Preface and Table of Contents of Familiar Letters on Chemistry. This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org. Familiar Letters on Chemistry and Its Relation to Commerce, Physiology and Agriculture by Eustis Liebig, MD, PhD, FRS, Professor of Chemistry in the University of Giesen, edited by John Gardner, MD. Preface. The letters contained in this little volume embrace some of the most important points of the science of chemistry in their application to natural philosophy, physiology, agriculture and commerce. Some of them treat of subjects which have already been or will hereafter be more fully discussed in my larger works. They were intended to be mere sketches and were written for the special purpose of exciting the attention of governments and an enlightened public to the necessity of establishing schools of chemistry and of promoting by every means the study of a science so intimately connected with the arts, pursuits and social well-being of modern civilized nations. For my own part, I do not scruple to avow the conviction that ere long a knowledge of the principal truths of chemistry will be expected in every educated man and that it will be as necessary to the statesman, the political economist and the practical agriculturalist as it is already indispensable to the physician and the manufacturer. In Germany, such of these letters as have already been published have not failed to produce some of the results anticipated. New professorships have been established in the universities of Gaungen and Würzburg for the express purpose of facilitating the application of chemical truths to the practical arts of life and of following up the new line of investigation and research, the bearing of chemistry upon physiology, medicine and agriculture, which may be said to be only just begun. My friend, Dr. Ernest Diefenbach, one of my first pupils, who is well acquainted with all the branches of chemistry, physics, natural history and medicine, suggested to me that a collection of these letters would be acceptable to the English public, which has so favorably received my former works. I readily acquiesced in the publication of an English edition and undertook to write a few additional letters, which should embrace some conclusions I have arrived at in my recent investigations in connection with the application of chemical science to the physiology of plants and agriculture. My esteemed friend, Dr. Gardner, has had the kindness to revise the manuscript and the proof sheets for publication, for which I cannot refrain expressing my best thanks. It only remains for me to add a hope that this little offering may serve to make new friends to our beautiful and useful science, and be a remembrance-er to those old friends who have, for many years past, taken a lively interest in all my labors. Eustis Liebig Geissen August 1843 Contents Letter 1 The subject proposed. Materials employed for chemical apparatus. Glass, cow chuck, cork, platinum, the balance. The elements of the ancients represent the forms of matter. Lavossier and his successors study of the materials composing the earth. Synthetic production of minerals. Lapis lazuli. Organic chemistry. Letter 2 Changes of form which every kind of matter undergoes. Conversion of gases into liquids and solids. Carbonic acid. Its curious properties in a solid state. Condensation of gases by porous bodies. By spongy platinum. Importance of this property in nature. Letter 3 The manufacture of soda from culinary salt. Its importance in the arts and in commerce. Glass, soap, sulfuric acid. Silver refining. Bleaching. Trade and sulfur. Letter 4 Connection of theory with practice. Employment of magnetism as a moving power. Its impracticability. Relation of coals and zinc as economic sources of force. Manufacture of beetroot sugar. Its impolicy. Gas for illumination. Letter 5 Isomerism or identity of composition in bodies with different chemical and physical properties. Crystallization, amorphism, isomorphism or similarity of properties in bodies totally different in composition. Letter 6 Alliance of chemistry with physiology. Division of food into nourishment and materials for combustion. Effects of atmospheric oxygen. Balance of carbon and oxygen. Letter 7 Animal heat. Its laws and influence on the animal functions. Loss and supply. Influence of climate. Fuel of animal heat. Agency of oxygen and disease. Respiration. Letter 8 Elements. Constituents of the blood. Fibrin, albumin, inorganic substances. Isomerism of fibrin, albumin and elements of nutrition. Relation of animal and vegetable organisms. Letter 9 Growth of animals. Uses of butter and milk. Metamorphoses of tissues. Food of carnivora and of the horse. Letter 10 Application of the preceding facts to man. Division of human food. Uses of gelatin. Letter 11 Circulation of matter in the animal and vegetable kingdoms. The ocean. Agriculture. Restitution of an equilibrium in the soil. Causes of the exhaustion of land. Virginia. England. Relief gained by importation of bones. Empirical farming unsatisfactory. Necessity for scientific principles. Influence of the atmosphere. Of saline and earthy matters in the soil. Letter 12 Science and art of agriculture. Necessity of chemistry. Rationale of agricultural processes. Washing for gold. Letter 13 Illustration of the necessity of chemistry to advance and perfect agriculture. Manner in which fallow ameliorates the soil. Uses of lime. Effects of burning. Of moral. Letter 14 Nature and effects of manures. Animal bodies subject to constant waste. Part separating. Exuviae. Waste vegetable matters. Together contain all the elements of the soil and of food. Various value of excrements of different animals as manure. Letter 15 Source of the carbon and nitrogen of plants. Produce of carbon in forests and meadows supplied only with mineral elements. Prove it to be from the atmosphere. Relations between mineral constituents and carbon and nitrogen. Effects of the carbonic acid and ammonia of manures. Necessity of inorganic constituents to the formation of elements. Of blood. And therefore of nutrition. Necessity of inquiries by analysis to advance agriculture. Letter 16 Results of the author's latest inquiries. Superlative importance of the phosphates of lime and alkalis to the cultivation of the cerealia. Sources of a supply of these materials. End of Table of Contents. Section 1 Of Familiar Letters on Chemistry. This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer please visit LibriVox.org. Recording by ML Co and Cleveland, Ohio March 2007. Familiar Letters on Chemistry. By Justice Liebig. Letter No. 1 My Dear Sir The influence which the science of chemistry exercises upon human industry, agriculture and commerce. Physiology, medicine and other sciences is now so interesting a topic of conversation everywhere that it may be no unacceptable present to you if I trace in a few familiar letters some of the relations it bears to these various sciences and exhibit for you its actual effect upon the present social condition of mankind. In speaking of the present state of chemistry, its rise in progress, I shall need no apology if, as a preliminary step, I call your attention to the implements which the chemist employs, the means which are indispensable to his labors and to his success. These consist generally of materials furnished to us by nature, endowed with many most remarkable properties fitting them for our purposes. If one of them is a production of art, yet its adaptation to the use of mankind, the qualities which render it available to us, must be referred to the same source as those derived immediately from nature. Cork, platinum, glass and kachuk are the substances to which I lewd and which minister so essentially to modern chemical investigations. Without them indeed we might have made some progress, but it would have been slow. We might have accomplished much, but it would have been far less than has been done with their aid. Some persons, by the employment of expensive substances, might have pursued the science, but in calculability your minds would have been engaged in its advancement. These materials have only been duly appreciated and fully adopted within the very recent period. In the time of la Loisier the rich alone can make chemical researches, the necessary apparatus could only be procured at a very great expense. And first, of glass. Everyone is familiar with most of the properties of this curious substance, its transparency, hardness, destitution of color and stability under ordinary circumstances. To these obvious qualities we may add those which especially adapted to the use of the chemist, namely that it is unaffected by most acids or other fluids contained within it. At certain temperatures it becomes more ductile and plastic than wax, and may be made to assume in our hands before the flame of a common lamp, the form of every vessel we need to contain our materials, and of every apparatus required to pursue our experiments. Then how admirable and valuable are the properties of quark, how little do men reflect upon the inestimable worth of so common a substance, how few rightly esteem the importance of it to the progress of science and the moral advancement of mankind. There is no production of nature or art equally adapted to the purposes to which the chemist applies it. Quark consists of a soft, highly elastic substance as a basis, having diffused throughout a matter with properties resembling wax, tallow and resin, yet dissimilar to all of these in termed subarin. This renders it perfectly impermeable to the fluids and in a great measure even to gases. It is thus the fittest material we possess for closing our bottles and retaining their contents. By its means and with the aid of kachuk, we connect our vessels and tubes of glass and construct the most complicated apparatus. We form joints and links of connection, adapt large apertures to small, and thus dispense all together with the aid of the brass founder and the mechanist. Thus the implements of the chemist are cheaply and easily procured, immediately adapted to any purpose and readily repaired or altered. Again, in investigating the composition of solid bodies, of minerals, we are under the necessity of bringing them into a liquid state, either by solution or fusion. Now vessels of glass, of porcelain, and of all non-metallic substances are destroyed by the means we employ for that purpose, are acted upon by many acids, by alkalis and the alkaline carbonates. Crucibles of gold and silver would melt at high temperatures, but we have a combination of all the qualities we can desire in platinum. This metal was only first adapted to these uses about 50 years since. It is cheaper than gold, harder and more durable than silver, infusible at all temperatures of our furnaces, and is left intact by acids and alkaline carbonates. Platinum unites all the valuable properties of gold and of porcelain, resisting the action of heat and of almost all chemical agents. As no mineral analysis could be made perfectly without platinum vessels had we not possessed this metal, the composition of minerals would have yet remained unknown. Without quark and kachuk, we should have required the costly aid of the machination at every step. Even without the latter of these adjuncts our instruments would have been far more costly and fragile, possessing all these gifts of nature we economize and calculate be our time, to us more precious than money. Such are our instruments. An equal improvement has been accomplished in our laboratory. This is no longer the damp, cold, fire-proof fault of the metallurgist, nor the manufacture of the joggest, fitted up with stills and retorts. On the contrary, a light, warm, comfortable room where beautifully constructed lamps supply the place of furnaces and the pure and odorless flame of gas, or of spirits of wine supersedes coal and other fuel and gives us all the fire we need, where health is not invaded, nor the free exercise of thought impeded. There we pursue our inquiries and interrogate nature to reveal her secrets. To these simple means must be added the balance, and then we possess everything which is required for the most extensive researches. The great distinction between the manner of proceeding in chemistry and natural philosophy is that one weighs the other measures. The natural philosopher has applied his measures to nature for many centuries, but only for fifty years have we attempted to advance our philosophy by weighing. For all great discoveries, chemists are indebted to the balance, that incomparable instrument which gives permanence to every observation dispels all ambiguity, establishes truth, detects error, and guides us in the true path of inductive science. The balance, once adopted as a means of investigating nature, put an end to the School of Aristotle and Physics. The explanation of natural phenomena by mere fanciful speculations gave place to a true natural philosophy. Fire, air, earth, and water could no longer be regarded as elements. Three of them could henceforth be considered only a significative of the forms in which all matter exists. Everything which were conversant upon the surface of the earth is solid, liquid, or error form. But the notion of the elementary nature of air, earth, and water so universally held was now discovered to belong to the errors of the past. Fire was found to be but the visible and otherwise perceptible indication of changes proceeding within the so-called elements. Lavoisier investigated the composition of the atmosphere and of water, and studied the many wonderful offices performed by an element common to both in the scheme of nature, namely oxygen, and he discovered many of the properties of this elementary gas. After his time, the principal problem of chemical philosophers was to determine the composition of the solid matter composing the earth. To the eighteen metals previously known were soon added twenty-four discovered to be constituents of minerals. The great mass of the earth was shown to be composed of metals in combination with oxygen, to which they are united in one, two, or more definite and unalterable proportions, forming compounds which are term metallic oxides, and these, again, combined with oxides of other bodies, essentially different to metals, namely carbon and silicon. If to these we add certain compounds of sulfur with metals, in which the sulfur takes the place of oxygen and forms sulfur-ets, and one other body, common salt, parenz which is composed of sodium and chlorine, close parenz, we have every substance which exists in a solid form upon our globe in any very considerable mass. Other compounds, enumerably various, are found only in small scattered quantities. The chemist, however, did not remain satisfied with the separation of minerals into their component elements, that is their analysis, but he sought by synthesis, that is by combining the separate elements and forming substances similar to those constructed by nature, to prove the accuracy of his processes and the correctness of his conclusions. Thus he formed, for instance, pumice stone, feldspar, mica, iron pirates, etc. artificially, but of all the achievements of inorganic chemistry, the artificial formation of lapis lazuli was the most brilliant and the most conclusive. This mineral, as presented to us by nature, is calculated powerfully to arrest our attention by its beautiful azure blue color. It's remaining unchanged by exposure to air or to fire, and furnishing us with the most valuable pigment, ultramarine, more precious than gold. The analysis of lapis lazuli represented it be composed of silica, alumina, and soda, three colorless bodies, with sulfur and a trace of iron. Nothing could be discovered in it of the nature of a pigment, nothing to which its blue color could be referred, the cause of which was searched for in vain. It might therefore have been supposed that the analyst was here altogether at fault, and that at any rate its artificial production must be impossible. Nevertheless, this has been accomplished and simply by combining in the proper proportions as determined by analysis silica, alumina, soda, iron, and sulfur. Thousands of pounds weight are now manufactured from these ingredients, and this artificial ultramarine is as beautiful as the natural, while for the price of a single ounce of the latter we may obtain many pounds of the former. With the production of artificial lapis lazuli, the formation of mineral bodies by synthesis ceased to be a scientific problem to the chemist. He has no longer sufficient interest in it to pursue the subject. He may now be satisfied that analysis will reveal to him the true constitution of minerals. But to the mineralogist and the geologist it is still in a great measure an unexplored field, offering inquiries of the highest interest and importance to their pursuits. After becoming acquainted with the constituent elements of all the substances within our reach and the mutual relations of these elements, the remarkable transmutation to which the bodies are subject under the influence of vital powers of plants and animals became the principal object of chemical investigations and the highest point of interest. A new science, inexhaustible as life itself, is here presented us, standing upon the sound and solid foundation of a well-established inorganic chemistry. Thus the progress of science is, like the development of nature's works, gradual and expansive. After the buds and branches spring forth, the leaves and blossoms. After the blossoms, the fruit. Chemistry, in its application to animals and vegetables, endeavors jointly with physiology to enlighten us respecting the mysterious processes and sources of organic life. End of Section 1, Recording by ML Cohen, Cleveland, Ohio, March 2007. Section 2 of Familiar Letters on Chemistry This is LibriVox Recording. LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org. Recording by ML Cohen, Cleveland, Ohio, March 2007. Familiar Letters on Chemistry by Justice Libig. Letter No. 2 My dear sir, In my former letter, I reminded you that three of the supposed elements of the ancients represent the forms or state in which all the ponderable matter of our globe exists. I would now observe that no substance possesses absolutely any one of those conditions, that modern chemistry recognizes nothing unchangeably solid, liquid or aeroform. Means have been devised for affecting a change of state in almost every known substance. Platinum, Illumina, and rock crystal, it is true, cannot be liquefied by the most intense heat of our furnaces. But they melt like wax before the flame of the oxyhydrogen blowpipe. On the other hand, of the twenty-eight gaseous bodies with which we are acquainted, twenty-five may be reduced to a liquid state and one into a solid. Probably, air long, similar changes of condition will be extended to every form of matter. There are many things related to this condensation of the gases worthy of your attention. Most aeroform bodies, when subjected to compression, are made to occupy a space which diminishes in the exact ratio of the increase of the compressing force. Very generally, under a force double or triple of the ordinary atmospheric pressure, they become one-half or one-third of their former volume. This was a long time considered to be a law, and known as the law of Marriott. A more accurate study of the subject has demonstrated that this law is by no means of general application. The volume of certain gases does not decrease in the ratio of the increase of the force used to compress them. But in some, a diminution of their bulk takes place in a far greater degree, as the pressure increases. Again, if amniacal gas is reduced by a compressing force to one-sixth of its volume, or carbonic acid is reduced to one-thirtysixth, a portion of them loses entirely the form of a gas and becomes a liquid which, when the pressure is withdrawn, assumes again in an instant its gaseous state. Another deviation from the law of Marriott. Our process for reducing gases into fluids is of admirable simplicity. A simple bent tube, or a reduction of temperature by artificial means, have superseded the powerful compressing machines of the early experimenters. The cyanuret of mercury, when heated in an open glass tube, is resolved into cyanogen gas and metallic mercury. If this substance is heated in a tube hermetically sealed, the decomposition occurs as before, but the gas, unable to escape and shut up in a space several hundred times smaller than it would occupy as a gas under the ordinary atmospheric pressure, becomes a fluid in that part of the tube which is kept cool. When sulfuric acid is poured upon limestone in an open vessel, carbonic acid escapes with effervescence as a gas, but if the decomposition is affected in a strong, close and suitable vessel of iron, we obtain the carbonic acid in the state of liquid. In this manner it may be obtained in considerable quantities, even many pounds of weight. Carbonic acid is separated from other bodies with which it is combined as a fluid under pressure of 36 atmospheres. The curious properties of fluid carbonic acid are now generally known. When a small quantity is permitted to escape into the atmosphere, it assumes its gaseous state with extraordinary rapidity and deprives the remaining fluid of caloric so rapidly that it congeals into a white crystalline mass like snow. At first indeed it was thought to be really snow, but upon examination it proved to be pure frozen carbonic acid. This solid, contrary to expectation, exercises only a feeble pressure upon the surrounding medium. The fluid acid enclosed in a glass tube rushes at once when opened into a gaseous state with an explosion which shatters the tube into fragments. But solid carbonic acid can be handled without producing any other effect than a feeling of intense cold. The particles of the carbonic acid being so closely approximated in the solid, the whole force of cohesive attraction, parense, which in the fluid is weak, close parense, becomes exerted and opposes its tendency to assume its gaseous state. But as it receives heat from surrounding bodies it passes into gas gradually and without violence. The transition of solid carbonic acid into gas deprives all around it of caloric so rapidly and to so great an extent that a degree of cold is produced immeasurably great, the greatest indeed known. Ten, twenty or more pounds weight of mercury bought into contact with a mixture of ether and solid carbonic acid becomes in a few moments firm and malleable. This however cannot be accomplished without considerable danger. A melancholy accident occurred at Paris which will probably prevent for the future of the formation of solid carbonic acid in these large quantities and deprive the next generation of the gratification of witnessing these curious experiments. Just before the commencement of the lecture in the laboratory of the Polytechnic School, an iron cylinder two feet and a half long and one foot in diameter in which carbonic acid had been developed for experiment before the class burst and its fragments were scattered about with the most tremendous force.  This vessel, formed of the strongest cast iron and shaped like a cannon, had often been employed to exhibit experiments in the presence of the students. You can scarcely think without shuddering of the dreadful calamity such an explosion would have occasioned in a hall filled with spectators. When we had ascertained the fact of gases becoming fluid under the influence of cold or pressure, a curious property possessed by charcoal, that of absorbing gas to the extent of many times its volume, ten, twenty, or even as in the case of ammoniocal gas or muriatic acid gas, eighty or ninety fold, which had been long known no longer remained a mystery. Some gases are absorbed and condensed within the pores of the charcoal into a space several hundred times smaller than they before occupied. And there is now no doubt that they there become fluid or assume a solid state, as in the thousand other instances chemical action hears the plant's mechanical forces. Adhesion or heterogeneous attraction, as it is termed, acquired by this discovery a more extended meaning. It had never before been thought of as a cause of change of state in matter, but it is now evident that a gas adheres to the surface of a solid body by the same force which condenses it into a liquid. The smallest amount of a gas, atmospheric air, for instance, can be compressed into a space a thousand times smaller by mere mechanical pressure, and then its bulk must be to the least measurable surface of a solid body as a grain of sand to a mountain. By the mere effect of mass, the force of gravity, gaseous molecules are attracted by solids and adhere to their surfaces. And when to this physical force is added the feeblest chemical affinity, the liquefiable gases cannot retain their gaseous state. The amount of air condensed by these forces upon a square inch of surface is certainly not measurable. But when a solid body, presenting several hundred square feet of surface within the space of a cubic inch, is bought into a limited volume of gas, we may understand why that volume is diminished, why all gases without exception are absorbed. A cubic inch of charcoal must have, at the lowest computation, a surface of one hundred square feet. This property of absorbing gases varies with different kinds of charcoal. It is possessed in a higher degree by those containing the most pores. That is, where the pores are finer. And in a lower degree, in the more spongy kinds, that is where the pores are larger. In this manner, every pore's body, rocks, stone, the clods of fields, etc., imbibe air, and therefore oxygen. The smallest solid molecule is thus surrounded by its own atmosphere of condensed oxygen. And if in their vicinity other bodies exist which have an affinity for oxygen, a combination is affected. When, for instance, carbon and hydrogen are thus present, they are converted into nourishment for vegetables, into carbonic acid and water. The development of heat when air is imbibed and the production of steam when the earth is moistened by rain are acknowledged to be consequences of this condensation by the action of surfaces. But the most remarkable and interesting case of this kind of action is the imbibition of oxygen by metallic platinum. This metal, when massive, is of lustrous white color, but it may be brought by separating it from its solutions into so finely divided a state that the particles no longer reflect light, and it forms a powder as black as soot. In this condition, it absorbs 800 times its volume of oxygen gas. And this oxygen must be contained within it in a state of condensation, verily like that, of fluid water. When gases are thus condensed, that is, their particles made to approximate in this extraordinary manner, their properties can be palpably shown. Their chemical actions become apparent as their physical characteristics disappear. The latter consists in the continual tendency of their particles to separate from each other. And it is easy to imagine that this elasticity of gaseous bodies is the principal impediment to the operation of their chemical force. For this becomes more energetic as their particles approximate. In that state in which they exist within the pores or upon the surface of solid bodies, their repulsion ceases, and their whole chemical action is exerted. Thus combinations which oxygen cannot enter into, decompositions which it cannot effect while in the state of gas, take place with the greatest facility in the pores of platinum containing condensed oxygen. When a jet of hydrogen gas, for instance, is thrown upon spongy platinum, it combines with the oxygen condensed in the interior of the mass. At their point of contact, water is formed, and as the immediate consequence, heat is evolved. The platinum becomes red hot, and the gas is inflamed. If we interrupt the current of the gas, the pores of the platinum become instantaneously filled again with oxygen. And the same phenomena can be repeated a second time, and so on, interminably. In finally pulverized platinum, and even in spongy platinum, we therefore possess a perpetual mobile, a mechanism like a watch which runs out and winds itself up, a force which is never exhausted, competent to produce effects of the most powerful kind, and self-renewed ad infinitum. Many phenomena, formerly inexplicable, are satisfactorily explained by these recently discovered properties of porous bodies. The metamorphosis of alcohol into acetic acid, by the process known as the quick vinegar manufacture, depends upon principles, at a knowledge of which we have arrived by a careful study of these properties. End of Section 2, recorded by ML Cohen, Cleveland, Ohio, March 2007. Section 3 of Familiar Letters on Chemistry. This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org, recording by Peter Yersley. Familiar Letters on Chemistry by Justice Leibig. Letter 3 My dear sir, the manufacture of soda from common culinary salt may be regarded as the foundation of all our modern improvements in the domestic arts, and we may take it as affording an excellent illustration of the dependence of the various branches of human industry and commerce upon each other and their relation to chemistry. Soda has been used from time immemorial in the manufacture of soap and glass, two chemical productions which employ and keep in circulation an immense amount of capital. The quantity of soap consumed by a nation would be no inaccurate measure whereby to estimate its wealth and civilisation. Of two countries, with an equal amount of population, the wealthiest and most highly civilised will consume the greatest weight of soap. This consumption does not subserve sensual gratification nor depend upon fashion, but upon the feeling of the beauty, comfort and welfare attendant upon cleanliness. And a regard to this feeling is coincident with wealth and civilisation. The rich in the Middle Ages concealed a want of cleanliness in their clothes and persons under a profusion of costly scents and essences, whilst they were more luxurious in eating and drinking, in apparel and horses. With us a want of cleanliness is equivalent to insupportable misery and misfortune. Soap belongs to those manufactured products, the money value of which continually disappears from circulation and requires to be continually renewed. It is one of the few substances which are entirely consumed by use, leaving no product of any worth. Broken glass and bottles are by no means absolutely worthless, for rags we may purchase new cloth, but soap water has no value whatever. It would be interesting to know accurately the amount of capital involved in the manufacture of soap. It is certainly as large as that employed in the coffee trade, with this important difference as respects Germany, that it is entirely derived from our own soil. France formally imported soda from Spain, Spanish sodas being of the best quality, at an annual expenditure of 20 to 30 millions of francs. During the war with England the price of soda and consequently of soap and glass rose continually and all manufacturers suffered in consequence. The present method of making soda from common salt was discovered by Le Blanc at the end of the last century. It was a rich boon for France and became of the highest importance during the wars of Napoleon. In a very short time it was manufactured to an extraordinary extent, especially at the seat of the soap manufacturers. Marseille possessed for a time a monopoly of soda and soap. The policy of Napoleon deprived that city of the advantages derived from this great source of commerce and thus excited the hostility of the population to his dynasty, which became favourable to the restoration of the Bourbons. A curious result of an improvement in a chemical manufacture. It was not long however in reaching England. In order to prepare the soda of commerce, which is the carbonate from common salt, it is first converted into Glauber's salt, sulphate of soda. For this purpose 80 pounds weight of concentrated sulphuric acid, oil of vitriol, are required to 100 pounds of common salt. The duty upon salt checked for a short time the full advantage of this discovery, but when the government repealed the duty and its price was reduced to its minimum, the cost of soda depended upon that of sulphuric acid. The demand for sulphuric acid now increased to an immense extent, and to supply it, capital was embarked abundantly as it afforded an excellent remuneration. The origin and formation of sulphuric acid was studied most carefully, and from year to year better, simpler and cheaper methods of making it were discovered. With every improvement in the mode of manufacture its price fell, and its sale increased in an equal ratio. Sulfuric acid is now manufactured in leadened chambers of such magnitude that they would contain the whole of an ordinary sized house. As regards the process into the apparatus this manufacture has reached its acme. Scarcely is either susceptible of improvement. The leadened plates of which the chambers are constructed, requiring to be joined together with lead, since tin or solder would be acted on by the acid. This process was until lately as expensive as the plates themselves, but now by means of the oxy hydrogen blowpipe, the plates are cemented together at the edges by mere fusion, without the intervention of any kind of solder. And then as to the process. According to theory 100 pounds weight of sulphur ought to produce 306 pounds of sulphuric acid. In practice 300 pounds are actually obtained. The amount of loss is therefore too insignificant for consideration. Again, saltpeter being indispensable in making sulphuric acid, the commercial value of that salt had formally an important influence upon its price. It is true that 100 pounds of saltpeter only are required to 1000 pounds of sulphur, but its cost was four times greater than an equal weight of the latter. Travellers had observed near the small seaport of Iquiqui in the district of Atacama in Peru, an efflorescence covering the ground over extensive districts. This was found to consist principally of nitrate of soda. Advantage was quickly taken of this discovery. The quantity of this valuable salt proved to be inexhaustible as it exists in beds extending over more than 200 square miles. It was brought to England at a less than half the freight of the East India saltpeter, nitrate of potasa. And as in the chemical manufacture, neither the potash nor the soda were required, but only the nitric acid. In combination with the alkali, the soda saltpeter of South America soon supplanted the potash, nitra of the East. The manufacture of sulphuric acid received a new impulse. Its price was much diminished without injury to the manufacturer. And with the exception of fluctuations caused by the impediments thrown in the way of the export of sulphur from Sicily, it soon became reduced to a minimum and remained stationary. Potash saltpeter is now only employed in the manufacture of gunpowder. It is no longer in demand for other purposes, and thus if government affect a saving of many hundred thousand pounds annually in gunpowder, this economy must be attributed to the increased manufacture of sulphuric acid. We may form an idea of the amount of sulphuric acid consumed when we find that fifty thousand pounds weight are made by a small manufacturer and from two hundred thousand to six hundred thousand pounds by a large one annually. This manufacture causes immense sums to flow annually into Sicily. It has introduced industry and wealth into the arid and desolate districts of Atacama. It has enabled us to obtain platina from its ores at a moderate and yet remunerating price, since the vats employed for concentrating this acid are constructed of this metal and cost from one thousand pounds to two thousand pounds of sterling. It leads to frequent improvements in the manufacture of glass which continually becomes cheaper and more beautiful. It enables us to return to our fields all their potash are most valuable and important manure in the form of ashes by substituting soda in the manufacture of glass and soap. It is impossible to trace within the compass of a letter all the ramifications of this tissue of changes and improvements resulting from one chemical manufacture, but I must still claim your attention to a few more of its most important and immediate results. I have already told you that in the manufacture of soda from culinary salt it is first converted into sulphate of soda. In this first part of the process the action of sulphuric acid produces muriatic acid to the extent of one and a half the amount of the sulphuric acid employed. At first the profit upon the soda was so great that no one took the trouble to collect the muriatic acid. Indeed it had no commercial value. A profitable application of it was however soon discovered. It is a compound of chlorine and this substance may be obtained from it purer than from any other source. The bleaching power of chlorine has long been known, but it was only employed upon a large scale after it was obtained from this residuary muriatic acid and it was found that in combination with lime it could be transported to distances without inconvenience. Henceforth it was used for bleaching cotton and but for this new bleaching process it would scarcely have been possible for the cotton manufacturer of Great Britain to have attained its present enormous extent. It could not have competed in price with France and Germany. In the old process of bleaching every piece must be exposed to the air and light during several weeks in the summer and kept continually moist by manual labour. For this purpose meadowland, eligibility situated, was essential. Now a single establishment near Glasgow bleaches 1400 pieces of cotton daily throughout the year. What an enormous capital would be required to purchase land for this purpose. How greatly would it increase the cost of bleaching to pay interest upon this capital or to hire so much land in England? This expense would scarcely have been felt in Germany. Besides the diminished expense, the cottonstuffs bleached with chlorine suffer less in the hands of skillful workmen than those bleached in the sun and already the peasantry in some parts of Germany have adopted it and find it advantageous. Another use to which cheap muriatic acid is applied is the manufacture of glue from bones. Bone contains from 30 to 36% of earthy matter, chiefly phosphate of lime, and the remainder is gelatin. When bones are digested in muriatic acid they become transparent and flexible like leather. The earthy matter is dissolved and after the acid is all carefully washed away pieces of glue of the same shape as the bones remain which are soluble in hot water and adapted to all the purposes of ordinary glue without further preparation. Another important application of sulfuric acid may be reduced, namely to the refining of silver and the separation of gold which is always present in some proportion in native silver. Silver, as it is usually obtained from mines in Europe, contains in 16 ounces 6 to 8 ounces of copper. When used by the silversmith or in coining 16 ounces must contain in Germany 13 ounces of silver in England about 14 and a half. But this alloy is always made artificially by mixing pure silver with the due proportion of the copper and for this purpose the silver must be obtained pure by the refiner. This is formally affected by amalgamation or by roasting it with lead and the cost of this process was about £2 for every 100 weight of silver. In the silver so prepared about 1, 1200 to 1, 2000th part of gold remained. To affect the separation of this by nitrio hydrochloric acid was more expensive than the value of the gold. It was therefore left in utensils or circulated in coin, valueless. The copper too of the native silver was no use whatever, but the 1,000th part of gold being about one and a half percent of the value of the silver now covers the cost of refining and affords an adequate profit to the refiner so that he affects the separation of the copper and returns to his employer the whole amount of the pure silver as well as the copper without demanding any payment. He is amply remunerated by that minute portion of gold. The new process of refining is a most beautiful chemical operation. The granulated metal is boiled in concentrated sulfuric acid which dissolves both the silver and the copper leaving the gold nearly pure in the form of a black powder. The solution is then placed in a lead and vessel containing metallic copper. This is gradually dissolved and the silver precipitated in a pure metallic state. The sulfate of copper thus formed is also a valuable product being employed in the manufacture of green and blue pigments. Other immediate results of the economical production of sulfuric acid are the general employment of phosphorus matches and of steering candles that beautiful substitute for tallow and wax. Twenty-five years ago the present prices and extensive applications of sulfuric and muriatic acids of soda, phosphorus, etc. would have been considered utterly impossible. Who is able to foresee what new and unthought of chemical productions ministering to the service and compass of mankind the next twenty-five years may produce? After these remarks you will perceive that it is no exaggeration to say we may fairly judge of the commercial prosperity of a country from the amount of sulfuric acid it consumes. Reflecting upon the important influence which the price of sulfur exercises and the cost of production of bleached and printed cotton stuffs, soap, glass, etc. and remembering that Great Britain supplies America, Spain, Portugal and the East with these exchanging them for raw cotton, silk, wine, raisins, indigo, etc. etc. We can understand why the English government should have resolved to resort to war with Naples in order to abolish the sulfur monopoly which the latter power attempted recently to establish. Nothing could be more opposed to the true interests of Sicily than such a monopoly. Indeed, had it been maintained a few years it is highly probable that sulfur, the source of her wealth, would have been rendered perfectly valueless to her. Science and industry form a power to which it is dangerous to present impediments. It was not difficult to perceive that the issue would be the entire cessation of the exportation of sulfur from Sicily. In the short period the sulfur monopoly lasted, 15 patents were taken out for methods to obtain back the sulfuric acid used in making soda. Admitting that these 15 experiments were not perfectly successful there can be no doubt it would, ere long, have been accomplished. But then in gypsum, sulfate of lime, and in heavy spa, sulfate of varieties we possess mountains of sulfuric acid. In galena, sulfate of lead, and in iron pyrites we have no less abundance of sulfur. The problem is how to separate the sulfuric acid or the sulfur from these native stores. Hundreds of thousands of pounds weight of sulfuric acid were prepared from iron pyrites while the high price of sulfur consequent upon the monopoly lasted. We should probably, ere long, have triumphed over all difficulties and have separated it from gypsum. The impulse has been given, the possibility of the process proved, and it may happen in a few years that the inconsiderate financial speculation of Naples may deprive her of that lucrative commerce. In like manner, Russia, by her prohibitory system, has lost much of her trade in tallow and potash. One country purchases only from absolute necessity from another, which excludes her own productions from her markets. Instead of the tallow and linseed oil of Russia, Great Britain now uses palm oil and coconut oil of other countries. Precisely analogous is the combination of workmen against their employers, which has led to the construction of many admirable machines for superseding manual labour. In commerce and industry every imprudence carries with it its own punishment. Every oppression immediately and sensibly recoils upon the head of those from whom it emanates. My dear sir, one of the most influential causes of improvement in the social condition of mankind is that spirit of enterprise which induces men of capital to adopt and carry out suggestions for the improvement of machinery, the creation of new articles of commerce, or the cheaper production of those already in demand. And we cannot but admire the energy with which such men devote their talents, their time and their wealth to realise the benefits of the discoveries and inventions of science. For even when these are expended upon objects wholly incapable of realisation, nay, even when the idea which first gave the impulse and proves in the end to be altogether impracticable or absurd, immediate good to the community generally ensues. Some useful and perhaps unlooked for result flows directly or springs ultimately from exertions frustrated in their main design. Thus it is also in the pursuit of science. Theories lead to experiments and investigations, and he who investigates will scarcely ever fail of being rewarded by discoveries. It may be indeed the theory sought to be established is entirely unfounded in nature, but while searching in a right spirit for one thing, the inquirer may be rewarded by finding others far more valuable than those which he sought. At the present moment electromagnetism as a moving power is engaging great attention and study. Wonders are expected from its application to this purpose. According to the sanguine expectations of many persons it will shortly be employed to put into motion every kind of machinery and amongst other things it will be applied to impel the carriages of railroads and this at so smaller cost that expense will no longer be matter of consideration. England is to lose her superiority as a manufacturing country in as much as her vast store of coals will no longer avail her as an economical source of motive power. We, say the German cultivators of this science, have cheap zinc and how small a quantity of this metal is required to turn a lathe and consequently to give motion to any kind of machinery. Such expectations may be very attractive and yet they are altogether illusory. They will not bear the test of a few simple calculations and these our friends have not troubled themselves to institute. With a simple flame of spirits of wine under a proper vessel containing boiling water a small carriage of 200 to 300 pounds weight can be put into motion or a weight of 80 to 100 pounds may be raised to a height of 20 feet. The same effects may be produced by dissolving zinc in dilute sulfuric acid in a certain apparatus. This is certainly an astonishing and highly interesting discovery but the question to be determined is which of the two processes is the least expensive? In order to answer this question and to judge correctly of the hopes entertained from this discovery let me remind you of what chemists denominate equivalents. These are certain unalterable ratios of effects which are proportionate to each other and may therefore be expressed in numbers. Thus if we require 8 pounds of oxygen to produce a certain effect and we wish to employ chlorine for the same effect we must employ neither more nor less than 35 and a half pounds weight. In the same manner 6 pounds weight of coal are equivalent to 32 pounds weight of zinc. The numbers representing chemical equivalents express very general ratios of effects comprehending for all bodies all the actions they are capable of producing. If zinc be combined in a certain manner with another metal and submitted to the action of dilute sulfuric acid it is dissolved in the form of an oxide. It is in fact burned at the expense of the oxygen contained in the fluid. A consequence of this action is the production of an electric current which if conducted through a wire renders it magnetic. In thus effecting the solution of a pound weight for example of zinc we obtain a definite amount of force adequate to raise a given weight one inch and to keep it suspended and the amount of weight it will be capable of suspending will be the greater the more rapidly the zinc is dissolved. By alternately interrupting and renewing the contact of the zinc with the acid and by very simple mechanical arrangements we can give to the iron an upward and downward or horizontal motion thus producing the conditions essential to the motion of any machinery. This moving force is produced by the oxidation of the zinc and setting aside the name given to the force in this case we know that it can be produced in another manner. If we burn the zinc under the boiler of a steam engine consequently in the oxygen of the air instead of the galvanic pile we should produce steam and buy it a certain amount of force. If we should assume which however is not proved that the quantity of force is unequal in these cases that for instance we had obtained double or triple the amount in the galvanic pile or that in this mode of generating force less loss is sustained we must still recollect the equivalence of zinc and coal and make these elements of our calculation. According to the experiments of desplets six pounds weight of zinc in combining with oxygen develops no more heat than one pound of coal consequently under equal conditions we can produce six times the amount of force with a pound of coal as with a pound of zinc it is therefore obvious that it would be more advantageous to employ coal instead of zinc even if the latter produced four times as much force in a galvanic pile as an equal weight of coal by its combustion under a boiler indeed it is highly probable that if we burn under the boiler of a steam engine the quantity of coal required for smelting the zinc from its ores we shall produce far more force than the whole of the zinc so obtained could originate in any form of apparatus whatever. Heat, electricity and magnetism have a similar relation to each other as the chemical equivalent of coal, zinc and oxygen by a certain measure of electricity we produce a corresponding proportion of heat or of magnetic power we obtain that electricity by chemical affinity which in one shape produces heat in another electricity or magnetism a certain amount of affinity produces an equivalent of electricity in the same manner as on the other hand a decompose equivalent of chemical compounds by a definite measure of electricity the magnetic force of the pile is therefore limited to the extent of the chemical affinity and in the case before us is obtained by the combination of the zinc and sulfuric acid in the combustion of coal the heat results from and is measured by the affinity of the oxygen of the atmosphere for that substance it is true that with a very small expense of zinc we can make an iron wire a magnet capable of sustaining a thousand pounds weight of iron let us not allow ourselves to be misled by this such a magnet could not raise a single pound weight of iron two inches and therefore could not impart motion the magnet acts like a rock which while at rest presses with a weight of a thousand pounds upon a basis like an enclosed lake without an outlet and without a fall but it may be said we have by mechanical arrangements given it an outlet and a fall true and this must be regarded as a great triumph of mechanics and I believe it is susceptible of further improvements by which greater force may be obtained but with every conceivable advantage of mechanism no one will dispute that one pound of coal under the boiler of a steam engine will give motion to a mass several hundred times greater than a pound of zinc in the galvanic pile our experience of the employment of electromagnetism as a motory power is however too recent to enable us to foresee the ultimate results of contrivances to apply it and therefore those who have devoted themselves to solve the problem of its application should not be discouraged in as much as it would undoubtedly be a most important achievement to supersede the steam engine and thus escape the danger of railroads even at double their expense Professor Weber of Gottingham has thrown out a suggestion that if a contrivance could be devised to enable us to convert at will the wheels of the steam carriage into magnets we should be enabled to ascend and descend aclivities with great facility this notion may ultimately be to a certain extent realised the employment of the galvanic pile as a motory power however must, like every other contrivance, depend upon the question of its relative economy probably some time hence it may so far succeed as to be adopted in certain favourable localities it may stand in the same relation to steam power as the manufacture of beet sugar bears to that of cane or as the production of gas from oils and resins to that from mineral coal the history of beet root sugar affords us an excellent illustration of the effect of prices upon commercial productions this branch of industry seems at length, as to its processes, to be perfected the most beautiful white sugar is now manufactured from the beet root in the place of the treacle-like sugar having the taste of the root which was first obtained and instead of three or four percent the proportion obtained by a card double or even treble that amount is now produced and notwithstanding the perfection of the manufacture it is probable it will, ere long, be in most places entirely discontinued in the years 1824 to 1827 the prices of agricultural produce were much lower than at present while the price of sugar was the same at that time one malta of wheat was ten shillings and one clafter of wood, eighteen shillings and land was falling in price readers note a malta was a measure containing several bushels but varying in different countries and a clafter was a cord, a stack measuring six feet every way end note thus food and fuel were cheap and the demand for sugar unlimited it was therefore advantageous to grow beet root and to dispose of the produce of land as sugar all these circumstances are now different a malta of wheat costs eighteen shillings a clafter of wood, thirty shillings to thirty-six shillings wages have risen but not in proportion while the price of colonial sugar has fallen within the limits of the German commercial league as for instance at Frankfurt on the main a pound of the whitest and best loaf sugar is seven pence the import's duty is thruppen's hapeny or thirty shillings per hundred weight leaving thruppen's hapeny as the price of the sugar in the year 1827 then one malta of wheat was equal to forty pounds weight of sugar whilst at present that quantity of wheat is worth seventy pounds of sugar if indeed fuel were the same in price as formerly and seventy pounds of sugar could be obtained from the same quantity of the root as then yielded forty pounds it might still be advantageously produced but the amount, if now obtained by the most approved methods of extraction falls far short of this and as fuel is double the price and labour dearer it follows that at present it is far more advantageous to cultivate wheat and to purchase sugar there are however other elements which must enter into our calculations but these serve to confirm our conclusion that the manufacturer of beet root sugar as a commercial speculation must cease the leaves and residue of the root after the juice was expressed were used as food for cattle and their value naturally increased with the price of grain by the process formerly pursued seventy five pounds weight of juice were obtained from one hundred pounds of beet root and gave five pounds of sugar the method of Schutzenbach which was eagerly adopted by the manufacturers produced from the same quantity of root eight pounds of sugar but it was attended with more expense to produce and the loss of the residue as food for cattle the increased expense in this process arises from the larger quantity of fuel required to evaporate the water for instead of merely evaporating the juice the dry residue is treated with water and we require fuel sufficient to evaporate a hundred and six pounds of fluid instead of seventy five pounds and the residue is only fit for manure the additional three pounds of sugar are purchased at the expense of much fuel and the loss of the residue as an article of food if the valley of the Rhine possessed mines of diamonds as rich as those of Golconda Viciapur or the Brazils they would probably not be worth the working at those places the cost of extraction is twenty eight shillings to thirty shillings the carrot with us it amounts to three or four times as much to more in fact than diamonds are worth in the market the sand of the Rhine contains gold and in the Grand Duchy of Barden many persons are occupied in gold washing when wages are low but as soon as they rise this employment ceases the manufacture of sugar from bead root in the like manner twelve to fourteen years ago offered advantages which are now lost instead therefore of maintaining it at a great sacrifice it would be more reasonable more in accordance with true natural economy to cultivate other and more valuable productions and with them purchase sugar not only with the state be the gainer but every member of the community this argument does not apply perhaps to France and Bohemia where the prices of fuel and of colonial sugar are very different to those in Germany the manufacture of gas for lighting from coal, resin and oils stands with us on the same barren ground the price of the materials from which gas is manufactured in England bears a direct proportion to the price of corn there the cost of tallow and oil is twice as great as in Germany but iron and coal are two thirds cheaper and even in England the manufacture of gas is only advantageous when the other products of the distillation of coal the coke etc can be sold it would certainly be esteemed one of the greatest discoverers of the age if anyone could succeed in condensing coal gas into a white, dry, solid, odourless substance portable and capable of being placed upon a candlestick or burned in a lamp wax, tallow and oil are combustible gases in a solid or fluid form which offer many advantages for lighting not possessed by gas they furnish in well constructed lamps as much light without requiring the expensive apparatus necessary for the combustion of gas and they are generally more economical in large towns or such establishments as hotels where coke is in demand and where losses in stolen tallow or oil must be considered as the labour of snuffing candles and cleaning lamps the higher price of gas is compensated in places where gas can be manufactured from resin, oil of turpentine and other cheap oils as at Frankfurt this is advantageous so long as it is pursued on small scale only if large towns were lighted in the same manner the materials would rise in price the whole amount at present produced would scarcely suffice for two such towns as Berlin and Munich but no just calculation can be made from the present prices of turpentine, resin, etc which are not produced upon any large scale End of Section 4 Section 5 of Familiar Letters on Chemistry This is a LibriVox recording All LibriVox recordings are in the public domain For more information or to volunteer please visit LibriVox.org recording by Peter Yersley Familiar Letters on Chemistry by Justice Leibig Letter 5 My dear sir, until very recently it was supposed that the physical qualities of bodies i.e. hardness, colour, density, transparency, etc and still more their chemical properties must depend upon the nature of their elements or upon their composition It was tacitly received as a principle that two bodies containing the same elements in the same proportion must of necessity possess the same properties We could not imagine an exact identity of composition giving rise to two bodies entirely different in their sensible appearance and chemical relations The most ingenious philosophers entertain to the opinion that chemical combination interpenetration of the particles of different kinds of matter and that all matter is susceptible of infinite division This has proved to be altogether a mistake If matter were infinitely divisible in this sense its particles must be imponderable and a million of such molecules could not weigh more than an infinitely small one But the particles of that imponderable matter which, striking upon the retina, give us the sensation of light not in a mathematical sense infinitely small Interpenetration of elements in the production of a chemical compound supposes two distinct bodies a and b to occupy one and the same space at the same time If this were so different properties could not consist with an equal and identical composition That hypothesis however shared the fate of innumerable imaginative explanations of natural phenomena in which our predecessors indulged They have now no advocate The force of truth dependent upon observation is irresistible A great many substances have been discovered amongst organic bodies composed of the same elements in the same relative proportions and yet exhibiting physical and chemical properties perfectly distinct one from another To such substances the term isomeric from iso, equal and meros, part is applied A great class of bodies known as the volatile oils oil of turpentine, essence of lemons oil of balsam, of copaiba oil of rosemary, oil of juniper and many others differing widely from each other in their odour in their medicinal effects, in their boiling point in their specific gravity etc are exactly identical in composition They contain the same elements carbon and hydrogen in the same proportions How admirably simple does the chemistry of organic nature present itself to us from this point of view An extraordinary variety of compound bodies produced with equal weights of two elements and how wide their dissimilarity The crystallized part of the oil of roses the delicious fragrance of which is so well known a solid at ordinary temperatures although readily volatile is a compound body containing exactly the same elements and in the same proportions as the gas we employ for lighting our streets and in short the same elements in the same relative quantities are found in a dozen other compounds all differing essentially in their physical and chemical properties These remarkable truths so highly important in their applications were not received and admitted as sufficiently established without abundant proofs Many examples have long been known where the analysis of two different bodies gave the same composition but such cases were regarded as doubtful At any rate they were isolated observations homeless in the realms of science At length examples were discovered of two or more bodies whose absolute identity of composition with totally distinct properties could be demonstrated in a more obvious and conclusive manner than by mere analysis that is they can be converted and re-converted into each other without addition and without subtraction In cyanuric acid, hydrated cyanic acid and cyanolide we have three such isomeric compounds Cyanuric acid is crystalline soluble in water and capable of forming salts with metallic oxides Hydrated cyanic acid is a volatile and highly blistering fluid which cannot be brought into contact with water without being instantaneously decomposed Ciamolide is a white substance very like porcelain absolutely insoluble in water Now, if we place the first cyanuric acid in a vessel hermetically sealed and apply a high degree of heat it is converted by its influence into hydrated cyanic acid and then if this is kept for some time at the common temperature it passes into cyanolide no other element being present and again inversely cyanolide can be converted into cyanuric acid and hydrated cyanic acid We have three other bodies which pass through similar changes in aldehyde, metalldehyde and etaldehyde and again two in urea and cyanuret of ammonia Further, 100 parts of aldehyde-hydrated butyric acid and acetic ether contain the same elements in the same proportion Thus one substance may be converted into another without addition or subtraction and without the participation of any foreign bodies in the change The doctrine that matter is not infinitely divisible but on the contrary consists of atoms incapable of further division alone furnishes us with a satisfactory explanation of these phenomena In chemical combinations the ultimate atoms of bodies do not penetrate each other they are only arranged side by side in a certain order and the properties of the compound depend entirely upon this order If they are made to change their place their mode of arrangement by an impulse from without they combine again in a different manner and another compound is formed with totally different properties We may suppose that one atom combines with one atom of another element to form a compound atom while in other bodies two and two four and four eight and eight are united so that in all such compounds the amount per cent of the elements is absolutely equal and yet their physical and chemical properties must be totally different the constitution of each atom being peculiar in one body consisting of two in another of four in a third of eight and in a fourth of sixteen simple atoms The discovery of these facts immediately led to many most beautiful and interesting results They furnished us with a satisfactory explanation of observations which were before veiled in mystery a key to many of nature's most curious recesses Again, solid bodies whether simple or compound are capable of existing in two states which are known by the terms amorphous and crystalline When matter is passing from a gaseous or liquid state slowly into a solid an incessant motion is observed as if the molecules were minute magnets they are seen to repel each other in one direction and to attract and cohere together in another and in the end become arranged into a regular form which under equal circumstances is always the same for any given kind of matter that is crystals are formed Time and the freedom of motion for the particles of bodies are necessary to the formation of crystals If we force a fluid or a gas to become suddenly solid leaving no time for its particles to arrange themselves and to cohere in that direction in which the cohesive attraction is strongest no crystals will be formed but the resulting solid will have a different colour a different degree of hardness and cohesion and will refract light differently in one word will be amorphous Thus we have cinnabar as a red and a jet black substance sulphur, a fixed and brittle body and soft, semi-transparent and ductile glass as a milk white opaque substance so hard that it strikes fire with steel and in its ordinary and well-known state These dissimilar states and properties of the same body are occasioned in one case by a regular in the other by an irregular arrangement of its atoms one is crystalline the other amorphous Applying these facts to natural productions we have reason to believe that clay, slate and many kinds of greywack are amorphous feldspar as transition limestone is amorphous marble basalt and lava mixtures of amorphous zeolite and orgyte Anything that influences the cohesion must also in a certain degree alter the properties of bodies carbonate of lime if crystallized at ordinary temperatures possesses the crystalline form hardness and refracting power of common spa if crystallized at a higher temperature it has the form and properties of aragonite Finally, isomorphism or the equality of form of many chemical compounds having a different composition tends to prove that matter consists of atoms the mere arrangement of which produces all the properties of bodies but when we find that a different arrangement of the same elements gives rise to various physical and chemical properties and a similar arrangement of different elements produces properties very much the same may we not inquire whether some of those bodies which we regard as elements may not be merely modifications of the same substance whether they are not the same matter in a different state of arrangement we know in fact the existence of iron in two states so dissimilar that in the one it is to the electric chain like platinum and in the other it is like zinc so that powerful galvanic machines have been constructed of this one metal among the elements are several instances of remarkable similarity of properties thus there is a strong resemblance between platinum and iridium bromine and iodine iron, manganese and magnesium cobalt and nickel phosphorus and arsenic but this resemblance consists mainly in their forming isomorphous compounds in which these elements exist in the same relative proportion these compounds are similar because the atoms of which they are composed are arranged in the same manner the converse of this is also true nitrate of strontia becomes quite dissimilar to its common state if a certain proportion of water is taken into its composition if we suppose selenium to be merely modified sulfur and phosphorus modified arsenic how does it happen we must inquire that sulfuric acid and selenic acid phosphoric and arsenic acid respectively form compounds which it is impossible to distinguish by their form and solubility were these merely isomeric they ought to exhibit properties quite dissimilar we have not I believe at present the remotest ground to suppose that any one of those substances which chemists regard as elements can be converted into another such a conversion indeed would presuppose that the element was composed of two or more ingredients and was in fact not an element and until the decomposition of these bodies is accomplished and their constituents discovered all pretensions to such conversions deserve no notice Dr. Brown of Edinburgh thought he had converted iron into rhodium and carbon or parasyanogen into silicon his paper upon this subject was published in the Transactions of the Royal Society of Edinburgh and contained internal evidence without a repetition of his experiments that he was totally unacquainted with the principles of chemical analysis but his experiments have been carefully repeated by qualified persons and they have completely proved his ignorance his rhodium is iron and his silicon an impure, incombustible coal This is a LibriVox recording while LibriVox recordings are in the public domain For more information or to volunteer please visit LibriVox.org Familiar Letters on Chemistry and its relation to commerce, physiology and agriculture by Eustace Liebig MD, PhD, FRS Professor of Chemistry in the University of Giesen Edited by John Gardner, MD Letter 6 One of the most remarkable effects of the recent progress of science is the alliance of chemistry with physiology by which a new and unexpected light has been thrown upon the vital processes of plants and animals We have no longer any difficulty in understanding the different actions of elements, poisons and remedial agents We have a clear conception of the causes of hunger of the exact nature of death We are not, as formerly, obliged to content ourselves with a mere description of their symptoms It is now ascertained with positive certainty that all the substances which constitute the food of man must be divided into two great classes one of which serves for the nutrition and reproduction of the animal body whilst the other ministers to quite different purposes Thus starch, gum, sugar, beer, wine, spirits, etc. furnished no element capable of entering into the composition of blood, muscular fiber, or any part which is the seat of the vital principle It must surely be universally interesting to trace the great change our views have undergone upon these subjects as well as to become acquainted with the researches from which our present knowledge is derived The primary conditions of the maintenance of animal life are a constant supply of certain matters, animal food and of oxygen in the shape of atmospheric air During every moment of life oxygen is absorbed from the atmosphere in the organs of respiration and the active breathing cannot cease while life continues The observations of physiologists have demonstrated that the body of an adult man supplied abundantly with food neither increases nor diminishes in weight during 24 hours and yet the quantity of oxygen absorbed into his system in that period is very considerable According to the experiments of Lavossier an adult man takes into his system from the atmosphere in one year no less than 746 pounds weight of oxygen. The calculations of Menzies make the quantity amount even to 837 pounds but we find his weight at the end of the year either exactly the same or different one way or the other by at most a few pounds What it may be asked has become of the enormous amount of oxygen thus introduced into the human system in the course of one year We can answer this question satisfactorily No part of the oxygen remains in the body but is given out again combined with carbon and hydrogen The carbon and hydrogen of certain parts of the animal body combined with the oxygen introduced through the lungs and skin and pass off in the forms of carbonic acid and vapor of water At every expiration and every moment of life a certain amount of its elements are separated from the animal organism having entered into combination with the oxygen of the atmosphere In order to obtain a basis for the approximate calculation we may assume with Lavoisier and Seguin that an adult man absorbs into his system 32 and one half ounces of oxygen daily that is 46,037 cubic inches equal to 15,661 grains French weight and further that the weight of the whole mass of the blood is 24 pounds of which 80% is water Now, from the known composition of the blood, we know that in order to convert its whole amount of carbon and hydrogen into carbonic acid and water 64.102 grains of oxygen are required This quantity will be taken into the system in 4 days and 5 hours Whether the oxygen enters into combination directly with the elements of the blood or with the carbon and hydrogen of other parts of the body It follows inevitably the weight of the body remaining unchanged in a normal condition that as much of these elements as will suffice to supply 24 pounds of blood must be taken into the system in 4 days and 5 hours and this necessary amount is furnished by the food We have not, however, remain satisfied with mere approximation We have determined accurately in certain cases the quantity of carbon taken daily in the food and of that which passes out of the body in the feces and urine combined that is, uncombined with oxygen And from these investigations, it appears that an adult man taking moderate exercise consumes 13.9 ounces of carbon which pass off through the skin and lungs as carbonic acid gas Footnote 1 This account is deduced from observations made upon the average daily consumption of about 30 soldiers in barracks The food of these men consisting meat, bread, potatoes, lentils, peas beans, butter, salt, pepper, etc was accurately weighed during a month and each article subjected to ultimate analysis Of the quantity of food, beer, and spirits taken by the men when out of the barracks we have a close approximation from the report of the sergeant And from the weight and analysis of the feces and urine it appears that the carbon which passes off through these channels may be considered equivalent of the amount taken in that portion of the food and of sauerkraut which was not included in the estimate It requires 37 ounces of oxygen to convert 13.9 of carbon into carbonic acid Again, according to the analysis of boson gold A horse consumes 79.1 ounces of carbon in 24 hours A milk cow 70.75 so that the horse requires 13 pounds 3.5 ounces and the cow 11 pounds 10.75 ounces of oxygen Footnote 2 17.5 ounces equals 0.5 kilogram As no part of the oxygen taken into the system of an animal is given off in any other form then combined with carbon or hydrogen and as a normal condition or state of health the carbon and hydrogen so given off are replaced by those elements in the food that the amount of nourishment required by an animal for its support must be in direct ratio with the quantity of oxygen taken into its system Two animals which in equal times take up by means of the lungs and skin unequal quantities of oxygen consume an amount of food unequal in the same ratio The consumption of oxygen in a given time may be expressed by the number of respirations It is therefore obvious that in the same animal the quantity of nourishment required must vary with the force and number of respirations A child breathes quicker than an adult and consequently requires food more frequently and proportionably in larger quantity and bears hunger less easily A bird deprived of food dies on the third day while a serpent confined under a bell respires so slowly that the quantity of carbonic acid generated in an hour can scarcely be observed and it will live three months or longer without food The number of respirations is fewer in a state of rest than during labor or exercise The quantity of food necessary in both cases must be in the same ratio An excess of food A want of due amount of respired oxygen or of exercise as also great exercise which obliges us to take an increased supply of food together with weak organs of digestion are incompatible with health But the quantity of oxygen received by an animal through the lungs not only depends upon the number of respirations but also upon the temperature of the respired air The size of the thorax of an animal is unchangeable We may therefore regard the volume of air which enters at every inspiration as uniform But its weight and consequently the amount of oxygen it contains is not constant Air is expanded by heat and contracted by cold An equal volume of hot and cold air contains an unequal amount of oxygen In summer atmospheric air contains water in the form of vapor It is nearly deprived of it in winter The volume of oxygen in the same volume of air is smaller in summer than in winter In summer and winter at the pole and at the equator we inspire an equal volume of air The cold air is warm during respiration and acquires the temperature of the body In order therefore to introduce into the lungs a given amount of oxygen Less expenditure of force is necessary in winter than in summer And for the same expenditure of force more oxygen is inspired in winter It is also obvious that in an equal number of respirations we consume more oxygen at the level of the sea than on a mountain The oxygen taken into the system is given out again in the same form both in summer and winter We expire more carbon at a low than at a high temperature and require more or less carbon than food in the same proportion And consequently more is respired in Sweden than in Sicily and in our own country an eighth more in winter than in summer Even if an equal weight of food is consumed in hot and cold climates infinite wisdom has ordained that very unequal proportions of carbon shall be taken in it The food prepared for the inhabitants of southern climes does not contain in a fresh state more than 12% of carbon while the blubber and train oil which feed the inhabitants of polar regions contains 66 to 80% of that element From the same cause it is comparatively easy to be temperate in warm climates or to bear hunger for a long time under the equator but cold and hunger united very soon produce exhaustion The oxygen of the atmosphere received into the blood in the lungs and circulated through every part of the animal body acting upon the elements of food is the source of animal heat End of Letter 6 My dear sir The source of animal heat its laws and the influence it exerts upon the functions of the animal body constitute a curious and highly interesting subject to which I would now direct your attention All living creatures whose existence depends upon the absorption of oxygen possess within themselves a source of heat independent of surrounding objects This general truth applies to all animals and extends to the seed of plants in the act of germination to flower buds when developing and fruits during their maturation In the animal body heat is produced only in those parts to which arterial blood and with it the oxygen absorbed in respiration is conveyed hair, wool and feathers receive no arterial blood and therefore in them no heat is developed The combination of a combustible substance with oxygen is under all circumstances the only source of animal heat In whatever way carbon may combine with oxygen the act of combination is accomplished by the disengagement of heat It is indifferent whether this combination takes place rapidly or slowly at a high or at a low temperature The amount of heat liberated is a constant quantity The carbon of the food being converted into carbonic acid within the body must give out exactly as much heat as if it had been directly burnt in oxygen gas or in common air The only difference is the production of the heat is diffused over unequal times In oxygen gas the combustion of carbon is rapid and the heat intense in atmospheric air it burns slower and for a longer time the temperature being lower In the animal body the combination is still more gradual and the heat is lower in proportion It is obvious that the amount of heat liberated must increase or diminish with the quantity of oxygen introduced in equal times by respiration Those animals therefore which respire frequently and consequently consume much oxygen possess a higher temperature than others which with a body of equal size to the heat take into their system less oxygen The temperature of a child 102 degrees is higher than that of an adult 99.5 degrees That of birds 104 degrees to 105.4 degrees is higher than that of quadrupeds 98.5 degrees to 100.4 degrees or than that of fishes or amphibia whose proper temperature is from 2.7 to 3.6 degrees higher than that of the medium in which they live All animals, strictly speaking are warm-blooded but in those only which possess lungs is the temperature of the body quite independent of the surrounding medium The most trustworthy observations prove that in all climates in the temperate zones as well as at the equator or the poles the temperature of the body in man and in what are commonly called warm-blooded animals is invariably the same Yet how different are the circumstances under which they live The animal body is a heated mass which bears the same relation to surrounding objects as any other heated mass It receives heat when objects are hotter It loses heat when they are colder than itself We know that the rapidity of cooling increases with the difference between the temperature of the heated body and that of the surrounding medium That is, the colder the surrounding medium the shorter the time required for the cooling of the heated body How unequal then must be the loss of heat in a man at Palermo where the external temperature is nearly equal to that of the body and in the polar regions where the external temperature is from 70 degrees to 90 degrees lower Yet notwithstanding this extremely unequal loss of heat experience has shown that the blood of the inhabitant of the Arctic circle has a temperature as high as that of the native of the south who lives in so different a medium This fact, when its true significance is perceived, proves that the heat given off to the surrounding medium is restored within the body with great rapidity This compensation must consequently take place more rapidly in winter than in summer at the pole than at the equator Now, in different climates the quantity of oxygen introduced to the system by respiration has been already shown varies according to the temperature of the external air The quantity of inspired oxygen increases with the loss of heat by external cooling and the quantity of carbon or hydrogen necessary to combine with this oxygen must be increased in the same ratio It is evident that the supply of heat lost by cooling is affected by the mutual action of the elements of the food and the inspired oxygen which combine together To make use of a familiar but not on that account a less just illustration the animal body acts in this respect as a furnace which we supply with fuel It signifies nothing what intermediate forms food may assume what changes it may undergo in the body The last change is uniformly the conversion of its carbon and its hydrogen into water The unassimilated nitrogen of the food along with the unburned or unoxidized carbon is expelled in the urine or in the solid excrements In order to keep up the furnace at a constant temperature we must vary the supply of fuel according to the external temperature that is, according to the supply of oxygen In the animal body the food or supply of oxygen we obtain the heat given out during its oxidation or combustion In winter when we take exercise in a cold atmosphere and when consequently the amount of inspired oxygen increases the necessity for food containing carbon and hydrogen increases in the same ratio and by gratifying the appetite thus excited we obtain the most efficient protection against the most piercing cold A starving man is soon frozen to death The animals of prey in those arctic regions as everyone knows far exceed in veracity those of the torrid zone In cold and temperate climates the air which incessantly strives to consume the body urges man to laborious efforts in order to furnish the means of resistance to its action while in hot climates the degree of labor to provide food is far less urgent Our clothing is merely an equivalent for a certain amount of food The more warmly we are clothed the less urgent becomes the appetite for food because the loss of heat by cooling and consequently the amount of heat to be supplied by food is diminished If we were to go naked like certain savage tribes or if in hunting or fishing with the same degree of cold as the Samoids we would be able with ease to consume ten pounds of flesh and perhaps a dozen of tallow candles into the bargain daily as warmly clad travelers have related with astonishment of these people We should then also be able to take the same quantity of brandy or train oil without bad effects because the carbon and hydrogen of these substances suffice to keep up the equilibrium between the external temperature and that of our bodies According to the preceding expositions the quantity of food is regulated by the number of respirations by the temperature of the air and by the amount of heat given off to the surrounding medium No isolated fact apparently opposed to this statement can affect the truth of this natural law without temporary or permanent injury to health The Neapolitan cannot take more carbon and hydrogen in the shape of food than he expires as carbonic acid and water and the Esquimax cannot expire more carbon and hydrogen than he takes into the system as food unless in a state of disease or of starvation Let us examine these states a little more closely The Englishman in Jamaica perceives with regret the disappearance of his appetite Previously a source of frequently recurring enjoyment and he succeeds by the use of cayenne pepper and the most powerful stimulants in enabling himself to take as much food as he was accustomed to eat at home but the whole of the carbon thus introduced into the system is not consumed The temperature of the air is too high and the oppressive heat does not allow him to increase the number of respirations by actual exercise and thus to proportion the waste to the amount of food taken disease of some kind therefore ensues On the other hand England sends her sick to southern regions where the amount of oxygen inspired is diminished in a very large proportion Those whose diseased digestive organs have in a greater or less degree lost the power of bringing the food into the state best adapted for oxidation and therefore are less able to resist the oxidizing influence of the atmosphere of their native climate obtain a great improvement in health The diseased organs of digestion have power to place the diminished amount of food in equilibrium with the inspired oxygen in the mild climate whilst in a colder region the organs of respiration themselves would have been consumed in furnishing the necessary resistance to the action of atmospheric oxygen In our climate Hepatatic disease or those arising from excess of carbon prevail in summer In winter pulmonary diseases or those arising from excess of oxygen are more frequent The cooling of the body produced increases the amount of food necessary The mere exposure to the open air in a carriage or on the deck of a ship by increasing radiation and vaporization increases the loss of heat and compels us to eat more than usual The same is true of those who are accustomed to drink large quantities of cold water which is given off at the temperature of the body 98.5 degrees increases the appetite and purses of weak constitution find it necessary by continued exercise to supply to the system the oxygen required to restore the heat abstracted by the cold water Loud and long continued speaking the crying of infants moist air all exert and decided and appreciable influence on the amount of food which is taken We have assumed that carbon and hydrogen especially by combining with oxygen serve to produce animal heat In fact, observation proves that hydrogen of the food plays a no less important part than the carbon The whole process of respiration appears most clearly developed when we consider the state of a man or other animal totally deprived of food The first effect of starvation is the disappearance of fat and this fat cannot be traced either in the urine or in the scanty feces Its carbon and hydrogen have been given off through the skin and lungs in the form of oxidized products It is obvious that they have served to support respiration In the case of a starving man 32.5 ounces of oxygen enter the system daily and are given out again in combination with a part of his body Curie mentions the case of an individual who was unable to swallow and whose body lost 100 pounds in weight during a month and according to Martel a fat pig overwhelmed in a slip of earth lived 160 days without food and was found to have diminished in weight in that time more than 120 pounds The whole history of hibernating animals and the well established facts of the periodical accumulation in various animals of fat which at other periods entirely disappears prove that the oxygen in the respiratory process consumes without exception all such substances as are capable of entering into combination with it It combines with whatever is present to it and the deficiency of hydrogen is the only reason why carbonic acid is the chief product for at the temperature of the body the affinity of hydrogen for oxygen far surpasses that of carbon for the same element We know in fact that the gramatoria expired a volume of carbonic acid equal to that of the oxygen inspired while the Carnovia the only class of animals whose food contains fat than is equal in volume to the carbonic acid expired Exact experiments have shown that in many cases only half the volume of oxygen is expired in the form of carbonic acid These observations cannot be gained and are far more convincing than those arbitrary and artificially produced phenomenon sometimes called experiments experiments which made as too often they are without regard to the necessary and natural conditions possess no value and may be entirely dispensed with especially when as in the present case nature affords the opportunity for observation and when we make a rational use of that opportunity In the progress of starvation however it is not only the fat which disappears but also, by degrees all such of the solids as are capable of being dissolved in the wasted bodies of those who have suffered starvation the muscles are shrunk and unnaturally soft and have lost their contractability all those parts of the body which are capable of entering into the state of motion have served to protect the remainder of the frame from the destructive influence of the atmosphere Towards the end the particles of the brain begin to undergo the process of octocidation aquarium, mania, and death close the scene that is to say all resistance to the oxidizing power of the atmospheric oxygen ceases and the chemical process of aromacosis or decay commences in which every part of the body the bones accepted enters into combination with oxygen the time which is required to cause death by starvation and fat in the body on the degree of exercise as in labor or exertion of any kind on the temperature of the air and finally on the presence or absence of water through the skin and lungs there escapes a certain quantity of water and as the presence of water is essential to the continuance of the vital motions its dissipation hastens death cases have occurred in which a full supply of water being accessible to the sufferer death has not occurred until after the lapse of 20 days in one case life was sustained in this way for the period of 60 days in all chronic diseases death is produced by the same cause namely the chemical action of the atmosphere when those substances are wanting whose function in the organism is to support the process of respiration when the diseased organs are incapable of performing their proper function of producing these substances when they have lost the power of transforming the food into that shape in which it may by entering into combination with the oxygen of the air protect the system from its influence then the substance of the organs themselves the fat of the body the substance of the muscles the nerves and the brain are unavoidably consumed the true cause of death in these cases is the respiratory process that is the action of the atmosphere a deficiency of food and a want of power to convert the food into a part of the organism are both equally a want of resistance and this is the negative cause of the secession of the vital processes the flame is extinguished because the oil is consumed and it is the oxygen of the air which has consumed it in many diseases substances are produced which are incapable of assimilation by the mere deprivation of food these substances are removed from the body without leaving a trace behind their elements have entered into combination with the oxygen of the air from the first moment that the function of the lungs or of the skin is interrupted or disturbed the body of the carbon appear in the urine which acquires a brown color over the whole surface of the body oxygen is absorbed and combines with all the substances which offer no resistance in those parts of the body where the access of oxygen is impeded for example in the armpits or in the soles of the feet peculiar compounds are given out recognizable by their appearance much carbon respiration is the falling weight and the bent spring which keeps the clock in motion and the inspirations and expirations are the strokes of the pendulum which regulate it in our ordinary timepieces we know with mathematical accuracy the effect produced on their rate of going by changes in the length of the pendulum or in the external temperature few however have a clear conception of the influence of air and temperature on the health of the human body and yet the research into the conditions necessary to keep it in the normal state is not more difficult than in the case of a clock