224 ANNUAL, REPORT SMITHSONIAN INSTITUTION, 1911. 



Commercially, we are as far from being able to produce artificial 

 diamonds as in the days of the alchemists. It is, perhaps, a bold 

 thing to say that no such thing as an artificial diamond will ever be 

 placed on the market, but one can safely assert that so far as our 

 knowledge stands at present it is impracticable. In saying this, I 

 am quite aware that statements as to the commercial production 

 of synthetic diamonds being an accomplished fact have quite recently 

 appeared broadcast in the public press, but those who are responsible 

 for such statements are, shall we say, under a misapprehension as to 

 the meaning generally conveyed by the term "synthetic," and are 

 unable to follow the distinction I have drawn between an artificial 

 gem and an imitation. 



To pass on to corundum, the problem of its artificial production is 

 very much simplified by the fact that its composition is oxide of 

 aluminium, and alumina- — which is, therefore, its amorphous equiv- 

 alent — fuses to a liquid under ordinary atmospheric pressure at a 

 temperature somewhere about 2,000° C. (the exact point has not as 

 yet been determined), and being the only stable oxide of a strongly 

 basic metal, it can be heated in air without any change. 



The chief problem to be faced, therefore, is that of attaining the 

 necessary temperature, and it is not surprising that crj^stalline 

 alumina was produced as a scientific curiosity as far back as the 

 commencement of the nineteenth century. It is at this time that we 

 first begin to hear of the oxy-hydrogen blowpipe (or the gas blow- 

 pipe as it was then called), and in a book published in 1819, 1 describ- 

 ing various experiments with this new apparatus, we read that 

 "two rubies were placed upon charcoal and exposed to the flame 

 of the gas blowpipe * * * after suffering it to become cold 

 * * • * the two rubies were melted into one bead." This hint 

 does not appear to have been followed up for some considerable time, 

 however, and the earlier experimenters in the production of artificial 

 gems worked in another direction; they were unable to obtain 

 products of commercial utility, because although they succeeded 

 in obtaining crystalline alumina, it was produced under conditions 

 which resulted in the formation of a mass of small crystals, almost 

 microscopic in size. Moreover, the form of these crystals was that 

 of the hexagonal plate which is the fundamental form of corundum, 

 and such a form would be useless for cutting even when of consider- 

 able area, owing to its thinness. Thus Gaudin, who appears to have 

 been one of the first to attain any success in this direction, obtained 

 a mass of such crystals by fusing alum and potassium sulphate in a 

 closed crucible. Ebelman obtained similar results by fusing alumina 

 with borax, and later Deville and Caron used aluminum fluoride 

 and boric acid. All these attempts yielded similar results, as in each 



» The Gas Blowpipe, by Dr. E. D. Clarke. 



