DIAMOND: ARTIFICIAL PRODUCTION S^T 



their success in producing artificial diamonds, it is only in quite recent years that absolutely 

 unquestionable results have been attained. The methods employed by various workers have, 

 as a rule, differed from each other ; thus in one case it has been sought to obtain diamonds 

 by fusing or volatilising carbon in the intense heat of the electric furnace ; in another by 

 the separation of carbon from one of its liquid compounds at ordinary temperatures, or at 

 a high temperature combined with great pressure. Some of the most important 

 investigations have been made by Despretz and Hannay, and of the more recent 

 experimenters Moissan has been most successful. Even the crystals obtained by Moissan 

 scarcely exceed microscropic size, so that though their scientific interest is great, they 

 are inapplicable as gems. 



In the experiments of Despretz (185B), electric sparks were continually passed through 

 a vacuum for a period exceeding a month ; the terminals made use of were respectively a 

 carbon cylinder and a platinum wire. At the conclusion of the experiment it was 

 found that the latter had received a coating of particles of carbon, which, under a 

 magnification of 30 diameters, appeared as small octahedra, and were said to scratch 

 corundum. In other experiments in which the terminals were a carbon point and a 

 platinum wire, the electric current was passed through acidulated water, and similar^ 

 though less marked, results were stated to have been obtained. In neither case, however, 

 were the particles of carbon proved beyond question to be diamond. 



In 1880 it was demonstrated by J. B. Hannay, a Scotch chemist, that metallic 

 sodium, and still more metallic lithium, is capable at a high temperature of separating 

 carbon from a hydrocarbon ; the same worker also claimed to have established the fact 

 that, at a high temper-ature and pressure, carbon could be separated in the same way from 

 nitrogenous organic substances. The investigation was carried out by placing lithium and 

 paraffin (the latter to play the part of a hydrocarbon) and a little sperm-oil in a very 

 strong, sealed, wrought-iron cylinder, which was then exposed to a very high temperature ; 

 the interaction of these substances thus took place under great pressure. It was hoped 

 that the carbon separated from the paraffin by the lithium would, at the moment of its 

 separation, dissolve in the sperm-oil, and that on cooling diamond would crystallise out 

 from this solution. A crystalline mass, containing 97 per cent, of carbon was indeed 

 obtained, but its identity with diamond is, as before, doubtful. 



Since 1893 more successful experiments having the same object in view have been 

 devised and performed by Moissan, the celebrated French chemist. He adopted the method 

 of causing carbon to dissolve in iron at the very high temperature of the electric furnace, 

 and then subjecting the molten mass to rapid cooling by immersing the crucible in which it 

 was contained in cold water, or by pouring the molten substance into a mould of iron 

 filings, or by other means. The object of the rapid cooling was to produce an exterior shell 

 of solid metal enclosing liquid material under tremendous pressure ; it was hoped that the 

 carbon crystallising out from the liquid under this great pressure would assume the form of 

 diamond, instead of gi-aphite as under ordinary conditions. At the close of the experiment, 

 the mass of iron was dissolved in acid, and some black grains and small, water-clear crystals 

 were obtained, which possessed all the properties of diamond and were completely 

 combustible in oxygen, yielding carbon dioxide as the sole product of combustion. The 

 largest crystals obtained by this method are about J millimetre (^f^ inch) in diameter ; 

 identical results are obtained when the experiment is performed with molten silver instead 

 of iron. There can no longer be any doubt that by this method it is possible to produce 

 genuine diamonds. 



Another successful method of producing artificial diamonds has been recently (1898) 



