The most important appHcation of the use of factors,
is the assay ton system devised by Prof Chandler. In
assaying ores of gold and silver, the precious metals are
always reported in ounces Troy per ton of 2000 pounds
avoirdupois. If a suitable number of grams, twenty-five
for instance, is taken and the gold and the silver weighed
in milligrams, a long calculation is required to convert
the results to ounces per ton. If however an assay ton
29.1666 grams, is used, the result in gold or silver as
weighed in milligrams is ounces to the ton without any
calculation.
The assay ton is derived as follows : —
One pound avoirdupois contains 7000 grains.
One ton, 2000 lbs., contains 14,000,000 grains.
One ounce Troy contains 480 grains.
CALCULATION AND USE OF FACTORS. 51

Therefore 14,000,000 -=- 480 or 29,166.6 is the number
of Troy ounces in 2000 lbs. avoirdupois ; so if we take
this number of milligrams for assay (29,166.6 +), each
milligram of gold or of silver found is an ounce Troy to
the ton in the ore : for

I : 29,166.6 + : : 480 : 14,000,000.
Therefore the assay ton is 29,166.6 + milligrams or
29.1666 + grams.
EXAMPLES.
1. Calculate the factors for NagO in Na2S04 and in
NaCl. Ans. 0.4368 and 0.5308.
2. Calculate the factors for Zn in ZnO, in ZnNH4
PO4 and in Zn2^2^'j.
Ans. 0.80345, 0.3664 and 0.4291.
3 . Calculate the factors forAsinAsgSa.inMggAsaOy
and AggAsO^. Ans. 0.6093, 0.4827 and 0.1621.
4. Calculate the factors for N, NH4 and NH4CI, for
weight of platinum from ignition of (N 1-14)2 PtClg.
Ans. 0.1441, 0.1752 and 0.5495.
5. What are the factors for conversion of Cr into
CrgOg, into PbCr04 and into BaCr04 ?

Ans. 1.4606, 6.1996 and 4.8656.
