CHEMICAL SCIENCE. 211 



evaporate gradually at a high heat constantly maintained. The process 

 is doubtless applicable to all minerals which are formed by the union of 

 their components at a high heat; but, although successful in practice, it 

 gave only microscopic crystals, and the other occupations and subsequent 

 death of the distinguished experimenter prevented him from prosecuting the 

 subject. Prof. Sainte-Claire Deville, in conjunction with Captain Caron, has 

 recently presented to the Academy of Sciences, at Paris, a new mode of 

 operating, by which, it appears, fine crystals of practical size may he ob- 

 tained. This method, which was probably suggested to the Professor dur- 

 ing his investigations on aluminum, consists (when the Corundum minerals 

 are sought) in establishing the reaction at a high heat between the fluoride 

 of aluminum and boracic acid. The fluoride is introduced into a black-lead 

 crucible, and above it is adjusted a small cupel containing the boracic acid; 

 the crucible is then tightly covered and protected from the action of the 

 air, and heated to a white heat for an hour. The two vapors decompose 

 each other, giving rise to alumina (Corundum), and the fluoride of Boron. 

 The crystals are rhombohedric with the faces of the regular hexagonal 

 prism : they have but one axis, and are negative, and possess all the optical 

 and crystallographic properties of natural Corundums, as well as their hard- 

 ness. The crystals produced were sometimes more than a centimetre (0'4 

 inch) long, and very broad, but are wanting in thickness. 



When the materials are used pure, the resulting crystals are of course col- 

 orless; but by adding a little of the fluoride of chromium to the fluoride of 

 aluminum, the colored gems, the ruby, the sapphire, or oriental emerald 

 may be produced, the colors depending solely upon the proportions of the 

 chrome used, which, in all cases, must be very small (except in the green 

 gem, M. Damour having detected twenty-five per cent, of oxide of chrome 

 in ouvarowite). The colors produced are identical with those found in 

 nature, and the gems retain their perfect transparency. In some cases 

 rubies and sapphires were produced alongside of each other. The zircons 

 and other analogous minerals were produced in a similar way. Chryso- 

 beryl, with its characteristic crystallization, was produced by mixed fluo- 

 rides of aluminum and glucinum treated as above; zahnite, from the fluo- 

 rides of aluminum and zinc; staurotide by substituting silica for the boracic 

 acid, or by heating alumina to a high temperature in a current of gaseous 

 fluoride of silicium. But all the silicates thus prepared arc very basic, 

 containing a very small portion of silica. Rutile was obtained by the 

 decomposition of a fusible titonate, especially titanate of protoxide of tin 

 by silica. 



" In making these experiments we often obtained in solution in the tin, a 

 brilliant substance, crystallizing in large metallic plates, separable from the 

 tin by hydro-chloric acid, which scarcely attacks them. This curious mate- 

 rial is an alloy of equal number of equivalents of iron and tin. This appear- 

 ance and chemical properties give it considerable interest." 



These researches are valuable not only from their applicability to the arts, 

 in which the artificial production of the hard minerals will greatly add to 

 our facilities, but also by their important bearing on the theory of the 

 formation of gems and the production of minerals in nature. 



ON THE FUSION OF MOLYBDENUM. 



Debray finds that pure metallic molybdenum completely withstands the 

 temperature at which platinum, quartz, etc., become liquid. The metal 



