THE ARTIFICIAL PRODUCTION OF DIAMOND. 
77 
Since my paper in 1907, the experiment of heating iron in a carbon crucible and 
transferring it to a steel die and subjecting it to 11,200 atmospheres pressure has 
been repeated, and it has been found that if the iron is allowed to set before the 
pressure is applied the amount of diamond is much greater than if pressed when very 
hot and molten, and that it is then about the same as when the crucible is cooled in 
water. The only reason that suggests itself to account for this is, that when 
pressure is applied while the iron is very hot some of the latter permeates the carbon 
of the crucible, and because of the greater specific heat and lesser conductibility of 
the carbon, the iron next to and in the carbon remains molten after the ingot has 
been cooled by direct contact with the steel cup on the face of the plunger. Thus, 
when cooling, the occluded gases have a free exit from the ingot, through the molten 
metal (which is pervious to gas) into the carl)on of the crucible, and are not retained 
in the ingot to the same extent as when it is set and enclosed in an envelope of 
colder iron impermeable to the gases before pressing. 
The experiments of Baraduc Muller (‘ Iron and Steel Institute, Carnegie 
Scholarship Memoirs,’ 1914, p. 216), on the extraction of gases from molten steel, 
showed that steel is permeable to gases down to 600° C. 
Other Experiments. 
The action of water on carbide of calcium, and of concentrated sulphuric acid on 
sugar for 6 hours under pressure of 30,000 atmospheres were tried ; in both cases 
amorphous carbon was formed and no diamond. 
Hannay’s experiments were repeated, where paraffin and dipple-oil with the alkali 
metals, especially potassium, were sealed in steel tubes and subjected to a red heat 
for several hours. The analysis gave no diamonds; in fact it became apparent that 
when hydrocarbons or water were relied on to produce pressure, the latter could only 
exist for a short time at the commencement, for when a red heat was reached the 
hydrogen escaped through the metal, and the oxygen combined with the steel. 
We did not analyse the steel tubes themselves. Many experiments were however 
tried with central heating under the press at 6000 atmospheres, and nothing was 
♦ obtained of interest with the substances used by Hannay, unless, as previously 
mentioned, some iron was present. Friedlander’s experiment was repeated, where a 
molten globule of olivine, in a reducing flame, or with carbon added, was stated by 
him to contain minute diamonds. An experiment was made with molten olivine in a 
carbon crucible in a wind furnace stirred with a carbon rod, with and without an 
electric current passing between the rod and crucible. 
Many experiments were also tried at 6000 atmospheres under the press with 
central heating with olivine associated with carbon, hydrocarbons, bisulphide of 
carbon, water, &c., also with blue ground from Kimberley instead of olivine. The 
results of the analyses were in all cases negative, except occasionally when metallic 
iron was present. Thus in some cases the olivine or blue ground, was partially 
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