Page:Proceedings of the Royal Society of London Vol 60.djvu/438

406 A brownish coloured precipitate was removed by filtration. It contained copper, lead, and silver, but no gallium. The filtrate was boiled to expel sulphuretted hydrogen, and the gallium precipitated with ammonia as described above. The precipitate was collected and ignited. It weighed 0*0288 gram.

This residue possessed a very light yellow colour. One milligram was burnt in the oxyhydrogen flame; its spectrum shows the two gallium lines very strongly. Lines of sodium, potassium, iron, calcium, and lead are present, but those of the last three are exceedingly weak.

The remaining 00278 gram of residue was fused with hydrogen potassium sulphate; water and sulphuric acid were added, and the crucible heated until fumes of sulphuric acid were evolved. Water was again added, and a small residue removed by filtration. This residue weighed 0'0040 gram.

The gallium was separated from the iron by two extractions with caustic soda solution. The ferric hydrate was dissolved in hydrochloric acid, and reprecipitated by ammonia. The ferric oxide weighed 0'0022 gram.

The gallium in the filtrate was then reprecipitated and weighed as oxide. It weighed 0'0213 gram.

A few drops of sodium phosphate were added to the filtrate, and sufficient ammonia to make it turn red litmus paper blue. After boiling for a few minutes the liquid was filtered, the paper being dried and burnt in the oxyhydrogen flame. The gallium lines are present in its spectrum, but are very weak.

The oxide of gallium now possessed a scarcely perceptible, faint yellow colour. It does not represent the whole of the gallium present in the sample, as a small quantity was removed and lost in testing the precipitations and residues; We are able, however, to estimate this quantity by comparing the lines in the different spectra with lines and spectra obtained by heating weighed quantities of gallium oxide. In this way we estimate the total quantity of gallium to be Prof. W. N. Hartley and Mr. H. Ram age. as follows:—

Pure oxide .................................. 0*0213 gram. In 0 001 gram of impure oxide.. . . 0*0008 „ In residue insoluble in HKSO4...*. 0*0004 „ In other substances, ........ 0 001 „ Ga»Os, total ................ 0 0235 gram. 0*0235 gram of pure Ga20 3 contains 0*0175 gram of gallium, equal to 0 100 _ Q.QQ304 per cent.

One part of gallium is contained in 33,000 parts of crude iron.