(2) _With Sulphuretted Hydrogen._--Two experiments with this gas, using in each 20 c.c. of the ferric chloride solution, and 10 c.c. of hydrochloric acid, required (after reduction) 20.2 c.c. and 20.1 c.c. of "permanganate." Repeating the experiments by passing the gas through a nearly boiling solution, but in other respects working in the same way, 21.3 c.c. and 21.6 c.c. of the permanganate solution were required. The sulphur was not filtered off in any of these. In another experiment, in which 50 c.c. of the ferrous sulphate solution were titrated with "permanganate," 48 c.c. of the latter were required. The titrated solution was next reduced with sulphuretted hydrogen, brought to the same bulk as before, and again titrated; 47.9 c.c. of the permanganate of potassium solution were required. (3) _With Sodium Sulphite._--Twenty c.c. of the ferric chloride solution, reduced with sodium sulphite, required 19.9 c.c. of "permanganate." In one experiment 50 c.c. of the ferrous sulphate solution were titrated with "permanganate"; 49.3 c.c. of the last-mentioned solution were required. The titrated solution was reduced with sodium sulphite, and again titrated; it required 49.2 c.c. of the permanganate of potassium solution. (4) _With Zinc._--Twenty c.c. of the ferric chloride solution, reduced with zinc and titrated, required 20.8 c.c. of "permanganate." Fifty c.c. of a solution of ferrous sulphate which required 49.7 c.c. of "permanganate," required for re-titration, after reduction with zinc, 49.7 c.c. The student should next practise the titration with bichromate, which is more especially valuable in the estimation of hydrochloric acid solutions. The following experiments are on the same plan as those already given. In each experiment (except when otherwise stated) there were present 20 c.c. of the ferrous chloride solution, and 10 c.c. of dilute hydrochloric acid, and the bulk was 300 c.c. ~Effect of Varying Temperature.~--The quantities of the bichromate of potassium solution required were as follows:-- Temperature 15° 30° 70° 100° Bichromate required 20.2 c.c. 20.3 c.c. 20.3 c.c. 20.4 c.c. ~Effect of Varying Bulk.~-- Bulk 50 c.c. 100 c.c. 200 c.c. 500 c.c. 1000 c.c. Bichromate required 20.4 " 20.4 " 20.4 " 20.5 " 20.8 " ~Effect of Varying Acid.~--In these, variable quantities of dilute hydrochloric acid were used. Acid present 10 c.c. 50 c.c. 100 c.c. Bichromate required 20.3 " 20.3 " 20.2 "