Page:Proceedings of the Royal Society of London Vol 60.djvu/433

Rh mefcal, the gallium lines are decidedly stronger in the spectra of the substances extracted from the metal.

One kilo, of finely powdered oi’e was mixed with dilute hydrochloric acid of double normal strength, measuring about 1250 c.c. Some carbon dioxide was disengaged and an insoluble residue left which was removed by filtration. The filtrate was then heated when a gelatinous separation of silica occurred. After evaporation to dryness, a further addition of hydrochloric acid yielded a solution 'which was not highly coloured, and, presumably, did not contain much iron. The silica rendered insoluble was removed by filtration, and to the filtrate ammonium chloride and ammonia were added. The precipitate thus formed was dissolved in hydrochloric acid, reduced with sulphur dioxide, nearly neutralised, and boiled with sodium thiosulphate. The precipitate was dissolved in hydrochloric acid and again precipitated by ammonia.

This precipitate was examined for gallium. The insoluble residue was also examined, and a comparison of the two spectra showed that a larger quantity of gallium remained in the insoluble residue than was extracted by the acid. It -was found that gallium could be extracted from this by fusion with caustic soda and lixiviation with water, and that the residue, after such treatment, contained no gallium. Operations on this particular ore w'ere suspended until other samples had been examined.

The following ores from the collection in the Royal College of Science, Dublin, were examined: —

1. Yorkshire clay ironstone from near Middlesbrough. 2. Clay ironstone from Grosmont, Whitby, Yorkshire. 3. Northamptonshire ore (clay ironstone). 4. Black band ore, Mount Melville mine, St. Andrews.

One kilo, of each was reduced to fine powder, and 100 grams of Nos. 1, 2, and 3, and 500 grams of No. 4 were extracted with dilute hydrochloric acid as in the previous case. In each sample gallium was found, but the proportion was very small in the Northamptonshire ore, and still more minute in the black band. Without operating on several hundred grams it would have been scarcely possible to detect the gallium in the Mount Melville ore. These ores had not been roasted, and in this they differed from the sample received from the North Eastern Steel Works. The effect of roasting is the same as increasing the proportion of gallium in the ore.

The sample weighing 575 grams consisted of 155 grams of fine powder and 420 grams of coarse powMer. The latter portion was heated with hydrochloric acid until the acid was nearly neutralised, when the liquid w'as decanted and filtered.