THE ARTIFICIAL PRODUCTION OF DIAM(JNL). 
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percentages of aluminium, magnesium, calcium, one or all are importajit; sulphur, 
manganese, and cobalt increase the yield, nickel appeared to be a disadvantage. An 
alloy of iron and 10 per cent, manganese, 10 per cent, cobalt, and 5 per cent, silicon 
gave out much gas when cooled slowly, and on quick cooling in water and mercury 
most of the spherules were burst and shredded. 
Finally about 1 to 3 per cent, of the other elements added to iron appeared to give 
the best results and the spherules were not then burst. 
An experiment was made by letting the ingot remain in the bed till it had quite 
set, hard enough to handle with the iron spoon, and then, cooled in water and 
mercury, it gave a fair diamond residue. 
Experiment.^ on the Conversion of Dincmond to (h-aphite. 
A clear octahedral diamond was placed in a small carbon crucible and packed 
loosely with Acheson graphite and heated for 10 minutes to about 1400° C. The 
diamond was coated with a firm layer of graphite. 
After two prolonged treatments with fuming nitric acid and potassium chlorate, 
alternating with boiling sulphuric acid and nitre, the opaque coating was removed 
and there remained a blackish translucent skin. When fractured the interior was 
unaltered and perfectly transparent. 
A piece of bort somewhat laminated, after the same treatment, showed the 
laminations separated by cracks starting from the outside. Upon breaking, the 
interior surface of the fissures showed an incipient change to graphite, but less rapid 
than on the outside surface. There was a sinuous pitting, deepest near the outside 
and diminishing inwards. The substance of the bort between the fissures was 
unaltered. 
The change of diamond to graphite under the conditions described is gradual, the 
surrounding gases, carbon monoxide, carbon dioxide, nitrogen, hydrogen, and also 
vapour of iron (as an impurity in the graphite) singly, or collectively, probably play a 
part, and further investigation as to this seems to be desirable. 
Sir James Dewar, in 1880, heated a diamond in a carbon tube to a temperature of 
2000° C., while a flow of pure hydrogen was maintained through the tube. The 
diamond soon became covered with a coating of graphite (‘ Proceedings of the Royal 
Institution ’). 
A clear diamond plunged into molten iron saturated with carbon at about 1400° C. 
for 5 minutes was deeply pitted. When removed from the iron small globules of iron 
adhered to the surface and the pits appeared to occur at these spots. 
A clear diamond was disintegrated by cathode rays, the temperature by pyrometer 
being 1890° C., the splinters were quite black and opaque, but after several prolonged 
treatments with fuming nitric acid and potassium chlorate, alternating with boiling 
sulphuric acid and nitre, the coating that remained was a dusky grey, but 
