In testing, the compound supposed to contain a chloride is
boiled with water, or, in some cases, dilute nitric acid. To the clear
solution containing nitric acid a few drops of nitrate of silver
solution are added. If, on shaking, a white curdy precipitate, soluble
in ammonia, separates out, it is sufficiently satisfactory evidence of
the presence of chlorides.
~Solution and Separation.~--The chlorides are generally soluble in
water, and are got into solution by extracting with warm dilute nitric
acid. Or, if insoluble, the substance is fused with carbonate of soda,
extracted with water, and the filtrate acidified with nitric acid. For
the determination, it is not necessary to obtain the solution of the
chloride free from other acids or metals. If tin, antimony, mercury, or
platinum is present, it is best to separate by means of sulphuretted
hydrogen. The chloride is determined in the solution after removal of
the excess of the gas. Where traces of chlorides are being looked for, a
blank experiment is made to determine the quantity introduced with the
reagents. One hundred c.c. of ordinary water contains from 1 to 3
milligrams of chlorine. On the addition of nitrate of silver to the
nitric acid solution, chloride of silver separates out. This is free
from other substances, except, perhaps, bromide and iodide.
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