88 
THE HON. SIR CHARLES ALGERNON PARSONS ; EXPERIMENTS ON 
conditions of the experiment operate to imprison the occluded gases, then the 
yield of diamond is about the same as if the crucible had been plunged into water, 
while if the conditions are such as to allow a free passage through the skin of the 
ingot, the yield is at once diminished, even though the bulk pressure on the ingot is 
the same. 
The experiment, on compressing acetylene and oxygen, has shown that minute 
crystals, probably diamond, are produced almost instantaneously in the molten 
surface of metal exposed on one side to gases consisting of carbon monoxide, 
carbon dioxide, and hydrogen at very high temperature and at 15,000 atmospheres. 
Sir William Crookes’ experiment desciibed in his lecture before the British 
Association at Kimberley in 1905 is somewhat analogous; cordite with a little 
additional carbon was fired in a chamber, the pressure I’eaching 8,000 atmospheres, 
a few crystals of diamond were found and isolated ; this result Crookes attributed 
to the melting of the carbon under the temperature of explosion and crystallization 
under the pressui'e on cooling. 
Under the conditions of the experiment there would be a considerable amount of 
the surface of the chamber melted and swept into the products of the charge by the 
turbulence of the explosion, and the spherules of iron would thus be carburized and 
cooled while still under heavy pressure. 
In the acetylene-oxygen experiment there is a molten surface with reducing gases 
on one side at high pressure, and on the other metal impervious to gases. In 
Crookes’ experiment the globules of metal are surrounded by gases at high pressure. 
In both cases the metal has solidified with the occluded gases imprisoned by the 
high external gaseous pressure, for we have seen that the pressure of occluded 
gases in highly carburized iron when quickly cooled cannot exceed about 1000 
atmospheres. 
The experiments under vacua from 75 mm. up to X-ray vacua Iiave shown 
generally that as the vacuum is increased the yield of diamond in the crucible is 
diminished, and that below 2 mm. none has been detected. But when alloys pre¬ 
viously boiled at atmospheric pressure are quickly heated up under high vacuum 
violent ebullition takes place, from the large volume of gases liberated, and some of 
the contents are ejected into the vacuum chamber before they have had time and 
sufficient temperature to part with their occluded gases, and diamond occurs in the 
spherules so ejected. 
The gases occluded in cast iron which are given off when heated in vacuo have 
been investigated by H. C. Carpenter and others, and the relative amounts of the 
constituents are found to vary widely according to the previous heat treatment and 
the nature of the gases in contact with the metal while molten and during cooling; 
they are carbon monoxide and carbon dioxide, hydrogen and nitrogen. 
H. C. Carpenter Journal of Iron and Steel Institute,’ 1911) states that, when 
heating up a bar of cast iron in vacno in a silica tube, “ After the twenty-fifth heat 
