DO 
THE HON. SIR CHARLES ALGERNON PARSONS: EXPERIMENTS ON 
It appears probable that concentration of gaseous pressure causes certain reactions 
• which bring about an association of carbon atoms in the tetrahedral form—-against 
their natural tendency to assume the more stable form of graphite.* 
The necessity of subjecting the iron to a temperature above 2000° C. before cooling 
would seem to imply the necessity of carbides of the other metals, such as silicon, 
magnesium, &c., being present to insure the necessary chemical reactions with the 
gases at high pressure within the ingot. 
In reviewing all our experiments, the greatest percentage of diamond occurred 
when the atmosphere around the crucible consisteil of 95 per cent, carbon monoxide 
and 1 per cent, hydrogen, 2 per cent, liydrocarbons, 2 per cent, nitrogen, the mean 
pressure in the vessel being about 1 inch absolute of mercury. The weight of 
diamond we estimated to be about I-t-20,000 of the weight of the iron. If we, for 
the moment, assume a volume of carbon monoxide at atmospheric pressure equal to 
0’69 that of the iron, the weight of carbon contained in it equals that of the diamond. 
For the following reasons it would appear that the formation of diamond in rapidly- 
cooled iron takes place when it is solid or in a plastic condition, or even at a still 
lower temperature. The rapid pitting of a diamond in highly carburized iron just 
above its melting point is so pronounced that the largest diamond hitherto produced 
artificially would be destroyed in a second or two if the iron matrix were molten. 
The production of diamond was obtained in an ingot rapidly cooled after it had set 
sufficiently hard to be handled in a spoon. A similar result was obtained in the case 
of a crucible placed in the die and subjected to 11,200 atmospheres pressure after the 
contents had set. Moissan found the diamonds to occur in the centre of the ingots 
both in the case of iron and also of silver. 
It has been seen that iron is permeable to carbon monoxide and hydrogen at 
temperatures above 600° C., and there appears to be no reason why the concentration 
of the occluded gases should not take place within the mass as effectively at 
600° C. as at higher temperatures, provided that they cannot escape. The most 
probable temperature, however, may be the point of recalescence at 690° C.f 
It would appear that the function of the impervious metal coating thrown around 
the ingot by quick cooling might be better effected by gas of the same composition 
as that whicli the metal ejects on cooling, the pressure being sufficient to ensure that 
the gaseous pressure around the ingot shall be equal to, or greater than could occur 
on quick cooling. Such a substitution might result in a larger gaseous content and a 
larger proportion of the ingot being brought into a suitable condition for the 
formation of diamond, and the yield might thereby be increased. Some gradations 
* It also appears that the conditions may operate to the exclusion of some gas or element inimical to 
the formation of diamond from certain parts of the metal, viz., the graphite liberated and the cooled 
metal of the outer layers may absorb some gas or element from the inner portion of the ingot and leave 
none for the central portion. 
t These conditions may also operate to exclude some gases from certain portions of the metal. 
