Temperature 10° C. 30° C. 70° C. 100° C. Sulphocyanate reqd. 19.6 c.c. 19.3 c.c. 19.0 c.c. 18.6 c.c. ~Effect of Varying Nitric Acid~:--Varying nitric acid has no effect, except that with a fairly acid solution the finishing point is somewhat sharper. Nitric acid added 5 c.c. 10 c.c. 20 c.c. 50 c.c. Sulphocyanate reqd. 19.6 c.c. 19.5 c.c. 19.6 c.c. 19.6 c.c. ~Effect of Varying Bulk~:-- Bulk 50 c.c. 100 c.c. 200 c.c. 300 c.c. Sulphocyanate reqd. 19.5 c.c. 19.6 c.c. 19.6 c.c. 19.7 c.c. ~Effect of Varying Ammonic Nitrate~:-- Ammonic nitrate 0 gram 1 gram 5 grams 10 grams Sulphocyanate reqd. 19.6 c.c. 19.6 c.c. 19.7 c.c. 19.9 c.c. ~Effect of Varying Silver~:-- Silver added 1 c.c. 10 c.c. 20 c.c. 50 c.c. 100 c.c. Sulphocyanate reqd. 1.0 c.c. 9.70 c.c. 19.6 c.c. 49.4 c.c. 99.0 c.c. This method is valuable for determining silver in salts, alloys, and solutions, where no more than an ordinary degree of accuracy is demanded. It is easy, and applicable under most of the usual conditions. Its greatest disadvantage is the brown coloration produced by the sulphocyanate when the assay is nearly, but not quite, finished; and the slowness with which this is removed on shaking up with the precipitate. This is worse with large quantities of precipitate, and if about 1 gram of silver is present, it gives an indefiniteness to the finish which lowers the precision of the process to about 1 in 500; this is useless for the assays of bullion. One writer states that this inconvenience is due to portions of liquid being entangled in the precipitate, but it appears much more likely to be due to the action of the precipitate itself. In attempting to apply the process to the assay of bullion by working it on the principle of a Gay-Lussac assay, it was found that a very considerable excess of silver was required to complete the reaction. In these experiments 100 c.c. of "sulphocyanate" (very accurately measured) was run into the solution containing the weighed portion of bullion (fine silver) and, after shaking the solution, was filtered. In the filtrate the remaining silver, if there should be any, was determined by the ordinary titration, but with "sulphocyanate" of one-tenth the strength. This final titration was quite satisfactory. The amount of silver precipitated by the first 100 c.c., however, varied with the quantity of silver present as in the following series.[17] Silver present. Silver precipitated. 1.1342 gram. 1.1322 gram. 1.1375 " 1.1335 " 1.1405 " 1.1351 " 1.1484 " 1.1379 "