A practical insight into chemistry, as affecting engineering, is
now considered essential for the complete education of an en-
gineer. As a pupil, the young engineer serves from three to six
months in the works' laboratory, and a precise description of
the methods of analysis of materials coming under the cog-
nisance of the practising engineer should prove of great ser-
vice to an engineering pupil, as well as a means of relief

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2 ENGINEERING CHEMISTRY.
to his tutor, who is often preoccupied otherwise than in
teaching.
The two main points to be considered in describing a
method of analysis are, (i) The strength of reagents used ; and
(2) The volume of reagents employed. It therefore becomes
necessary to have a stock of reagents of definite strength at
hand in the laboratory. As a general rule, in instructions
for analysis, the specific gravity of the desired solution or
one part of a strong reagent diluted so many times, is re-
ferred to as a means of indicating the solution to be employed;
but this mode of expressing strength is not veiy definife or
convenient. The best system of reagents with which I am
acquainted is that devised by Mr. J. Reddrop, F.I.C., the
chemist of the London and North -Western Railway. This
system (it will be found) has been followed as far as possible
throughout this work, my own experience having led me to
fully endorse the claims of its author (see post, page 14) as to
t)ie advantages to be secured by the employment of the system.
