GEMS, ARTIFICIAL (ante). Artificial gems, properly so-called, are identical in properties and chemical composition with the natural gems. The chemical composition of minerals, including gems, unlike crystallized salts, varies within limits. The prodUc tion of artificial gems is interesting for two reasons: first, scientifically, from the light thrown upon the conditions under which gems are formed in nature; second, coinmer• daily, as foreshadowing the time when they can be made of a size, and at a cost, which will render their manufacture profitable.
Although methods for the artificial production of rubies and sapphires have been known—at least since 1858—the results communicated to the Parisian Academy by MM. E Fremy and Feil in the latter part of 1877 are far more satisfactory. Rubies and sapphires are colored corundums; therefore, the first prOblem is the formation of corundiims which are composed of alumina (Al201), and, after that has been solved it is necessary only to incorporate with the corundum mixture the proper metallic oxides to obtain the gems. The theory upon which these experimenters worked was to displace the alumina from its silicate by fusion with a base having a stronger combining power with the silicic acid. The best results were obtained by placing equal parts of porcelain-clay and red-lead in a large crucible, enclosing this in a second, and exposing them for several weeks to an intense red heat in a glass furnace. Two crucibles are necessary, as the lead combines with the silica of the inner one and eats boles through it. Upon allowing the crucibles to cool and breaking the inner one, two strata were found, an upper glassy one, chiefly of silicate of lead, and a lower one containing clusters of corundum crystals. The silicate of lead was removed by melting with oxide of lead or potash. These crystals cut glass, rock crystals. and even topaz, and are exceeded in hardness by only the diamond and crystalline boron. By adding two or three per cent of bich•omate of potash, rubies were formed; while sapphires were obtained by using a smaller quantity of bichromate of potash and still less of oxide of cobalt. These gems *Ehelmen's memoirs on this department of chemist are contained in the first volume of ; tai's Recueil des Travaux Scientifiques de .11, Ebeinien. Puns, 16.55.
presented qualities in every respect like the natural ones, while diamond cutters who ground the rubies found them harder; they will probably outwear the natural rubies when used in watches.
At the same meeting at which the memoir of MM. Fremy and Fell was presented, M. Monuier announced that upon cautiously pouring a very dilute solution of oxalic acid upon a solution of silicate of soda as thick as molasses, the, separated slowly and was deposited, forming opals. By using a solution of nickelous sulphate, apple-green stores such as chrysoprase were formed.
Since 1828 many attempts have been made to produce diamonds by various methods, some of which claim to have been successful. Feb. 26, 1880, Mr. J. B. Hanney, of Glasgow, Scotland, read a preliminary notice before the Royal Society " On the Artifi cial Formation of the Diamond," and exhibited a number which he had made. In experimenting upon the solubility of solids in vapors immediately beyond the "critical point"—i.e., matter in transita between the liquid and gaseous states—Mr. Ilanney found that the solvent power of water was-greatly increased, even dissolving to a considerable extent alumina and silica, which are unaffected under ordinary conditions. He further found that upon withdrawal or dilution of the solvent gas, crystalline solids were deposited. These facts suggested the possibility that a solvent might be for carbon, and diamond crystals be deposited from this solution. After a number of unsuccessful experiments upon the common forms of carbon—charcoal, lampblack, and black-lead he turned to indirect methods. Remembering that'. the elements are much more ener getic in their action when nascent, or just set free from combination, and having ascer tained that upon heating a gas containing hydrogen and carbon, under pressure, in the presence of a metal, the metal attracts the hydrogen and liberates the carbon—it remained only to find a solvent for the nascent carbon, and this he finally found. His method was as follows: In a strong iron tube 20 inches long, 4 inches in diameter, and having a bore of one-half inch; some lithium, and a mixture of highly rectified bone-oil and paraffine-spirit were placed, and the end securely closed with a screw plug. After heating the tube for 14 hours and allowing it to cool, it was opened and, after the gas had passed out, a hard smooth mass was discovered at the upper end of the tube. Upon removing and pulverizing this mass, some hard particles were found which were tested. by Profs. Maskelyne, Roscoe, and Dewar, and declared to be diamonds. Mr. Hanney'w experiments proved the necessity for the presence of a stable compound containing nitrogen: Thus far it has cost five pounds to produce five shillings' worth of diamond, but further researches will undoubtedly cheapen the process. This is justly considered to be a triumph of chemistry, removing the reproach that, while chemists had built up synthethically many complex organic compounds, they had not produced a diamond composed, as it is, of the single element carbon that underlies the whole. And, among the achievements of the future may be the production of a Koh-i-noor, though, in this case, Nature holds great odds against man, as immense periods of time and great pres sures—which are required for the growth of minerals—tax neither her powers nor her patience.