Journal of the Mining Institute of Japan

Copper blast furnace slag produced from Shisakajima Smelter contains more than 30% of iron. So we stad ed the methods of recovering iron and manufacturing Fort land cement from the residue by means of rotary kiln. And.we got satisfacaory results regarding the r covery of iron mainl as pig iron aud partially as loops, as well as the manufacture of Portland Cament from the resi ue. in this case the reeove: ed yield of iron was about 90% and the character of Portland cement was excellent enough to be far better than the standard quality. iu J. E. S.

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It is well known that lead salts are advantageous for silver cyanidation, by removing. sulp ions and by accelerating the dissolution of silver sulphide. But the effect of lead salts on the rate of dissolution of gold has not yet been investigated.
To find out the effect of varying amount of lead acetate on the dissolution of gold, determination of the rate of dissolution ofgold in 0.03 per cent, 0.08 per cent, 0.14 per cent and 0.20 per cent potassium cyanide solutions were made. It is found that, in 0.03 per cent and. 0.08 per cent potassium cyanide solutions, the lead acetate accelerates the dissolution of gold, when, fresh gold plate is used but it frequently retards the dissolution of gold making its surface passive when the same plate is used in repetition. In 0.14 per cent and 0.20 per cent potassium cyanide solutithis the lead acetate always accelerates the dissolution of, gold, even in the case of repeated immersion of the plate
The author conjectures that it is provable that gold in some way reacts with lead acetate, resulting the precipitation of metallic lead on the gold plate and the entry of gold into solution, as lead is electronegative to gold in cyanide solution, and that this fact perhaps accounts for the accelerated dissolution of gold. It seems also provable that passivity of gold is dne to the fact that the gold is filmed with insoluble leadoxycyanide which prevents the further dissolution of gold. The existence of lead on the gold plate is detected by the separate experiments using dithizon solution, in both cases of accelerated and retarded dissolution.
II. The effect of simultaneous addition of calcium hydroxide and lead acetate on the rate of dissolution of gold.
In these expeiments, the author finds that the effect of lead acetate on the dissolution rate of gold is more remarkable than that of calcium hydroxide and that the high concentration of calcium bydroxide and lead acetate almost completly inhibits the dissolution of gold.

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