Page:Proceedings of the Royal Society of London Vol 60.djvu/43

Rh There is still evidence of liquation of gold towards the centre, but comparison of fig. 12 with those which immediately precede it will show how greatly the arrangement of the alloy has been modified by the presence of the additional 8 per cent, of silver. The proportion of silver in this alloy was proved by assay to be 15‘5 per cent.

As there was still evidence of liquation, the metal was cast with still more silver, making 20 per cent, of silver in all. The alloy, when cast into a mould, proved to be almost uniform in composition, the difference between the centre and the extreme portions being very slight.

Liquation had practically ceased, a fact which proves incontestably that silver is the solvent for the base metals, zinc and lead, when they are alloyed with gold.

Conclusions.—(1) Alloys of gold with base metals, notably with lead and zinc, now largely often met with in industry, have the gold concentrated towards the centre and lower portions, which renders it impossible to ascertain their true value with even an approximation to accuracy.

(2) When silver is also present these irregularities are greatly modified. The method of obtaining “ cooling-curves ” of the alloys shows that the freezing points are very different when silver is present and when it is absent from the alloy.

(3) This fact naturally leads to the belief that if the base metal present does not exceed 30 per cent., silver will dissolve it and form a uniform alloy with gold.

(4) This conclusion is sustained by the experiments illustrated by figs. 9, 10, 11, 12, which, in fact, gradually lead up to it, and enable a question of much interest to be solved.

In the course of an investigation of flame spectra at high temperatures (‘ Phil. Trans.,’ A, vol. 185, pp. 1029—1091 (1894) ) extended to the basic Bessemer process, the authors were occupied last July and August in observing the flames from the converters at the North -Eastern Steel Company’s Works, at Middlesbrough-on-Tees. A large number of photographs were taken in series during the progress of the “ blow,” and also of the “ after blow,” but these will