Page:Proceedings of the Royal Society of London Vol 60.djvu/437

Rh adding a few drops of ammonia; if any precipitate was produced it was collected and added to the other precipitate. The precipitate in this case was added to ferrocyanide precipitates obtained from the residue W.T,he paper, after being scraped to remove the residue as far as possible, was burnt in the oxyhydrogen flame. The gallium lines are strong.

The ferrocyanide precipitates with others rich in gallium were ignited at low redness to decompose the cyanides, and then fused with pure caustic soda. The produce was extracted with water and filtered.

Residue from Fusion.—Dissolved in hydrochloric acid, expelled the excess of acid, added water, reduced the ferric salt, and filtered. Residue remaining contained only a trace of gallium.

Filtrate.—Boiled with an excess of ammonium acetate and filtered off the precipitate. The filtrate was mixed with sodium phosphate and boiled, thus yielding a second precipitate. The filtrate from this was again boiled, and ammonium carbonate added until a third precipitate was produced. Very small portions of these three precipitates were burnt in the oxyhydrogen flame. The first two were rich in gallium, while the third contained only a trace. Ignited the first and second precipitates, heated the residue in a platinum crucible with hydrochloric and sulphuric acids, expelled the former acid by heating until the white fumes of sulphuric acid were evolved, and then fused the residue with caustic soda. Extracted with water and filtered. After a second fusion the residue was practically free from gallium. The alkaline filtrates were acidified with hydrochloric acid, and the gallium precipitated by boiling with ammonia until the excess of ammonia was expelled. Filtered and tested the filtrate by repeating the process of boiling with ammonia until no further precipitate resulted.

The precipitates of gallium hydrate and phosphate, obtained as described, were dissolved in hydrochloric acid and, after adding onefourth the volume of the solution of strong hydrochloric acid, an excess of potassium ferrocyanide was added. After standing for one day the precipitate was collected, washed, and ignited. It weighed 00670 gram.

This residue was dissolved by heating with strong sulphuric acid in a platinum crucible, some water being added, after heating strongly, and then an excess of caustic soda prepared from sodium. The crucible was then heated until the water was expelled, and the residue retained in the fused caustic soda. The process was repeated on the residue which remained after adding water and filtering. The second residue was practically free from gallium.

The filtrates were collected in a platinum basin, made faintly acid with hydrochloric acid, and saturated with sulphuretted hydrogen.