Water added none 100 c.c. 200 c.c. 400 c.c. Silver required 47.0 c.c. 47.0 c.c. 47.0 c.c. 47.05 c.c. Very considerable dilution therefore has no effect. ~Effect of varying soda.~--The conditions were those of the 40 c.c. experiment in the first series, except that varying amounts of soda solution were used. Soda added none 10 c.c. 30 c.c. Silver required 46.95 c.c. 47.0 c.c. 47.0 c.c. This alkali therefore has no prejudicial effect. ~Effect of ammonia.~--Soda causes turbidity in some cyanide liquors; with these it should be replaced by 2 or 3 c.c. of dilute ammonia with a gram or so of ammonium chloride. The following experiments with dilute ammonia show that larger quantities of this reagent must be avoided. Ammonia added none 10 c.c. 30 c.c. 60 c.c. Silver required 46.95 c.c. 47.15 c.c. 47.7 c.c. 49.5 c.c. ~Effect of sodium bicarbonate.~--In this experiment 1 gram of bicarbonate of soda was used instead of the soda or ammonia of the other experiments. The silver nitrate required was only 46.45 c.c. instead of the 47.0 c.c. which is the normal result. This is probably due to the liberation of prussic acid and shows the importance of having the solution alkaline. ~Effect of zinc.~--In each experiment 40 c.c. of the cyanide solution and .5 gram of zinc sulphate crystals were used and the bulk was made up to 100 c.c. before titrating. Soda added 1 c.c. 5 c.c. 10 c.c. 25 c.c. Silver required 47.1 c.c. 47.0 c.c. 46.9 c.c. 46.9 c.c. The work was easier with the more alkaline solutions. The titration in the presence of zinc is comparatively easy, but, in learning it, it is well to have a burette with cyanide so that if a titration be overdone it can be brought back by the addition of 1 or 2 c.c. more cyanide and the finish repeated; a quarter of an hour's work in this way will ensure confidence in the method. ~Effect of other substances.~--It was found that an alkaline cyanate, sulphocyanate, ferrocyanide, nitrite, borate, silicate or carbonate has no effect. The ferricyanide had a small influence and, as might be expected, hyposulphite is fatal to the assay. The addition of salts of lead and cadmium was without effect. On the other hand, nickel produces its full effect; and the quantity of nickel added can be calculated with accuracy from the extent of its interference with the titration.