The synthesis of a silicalcyanide and of a felspar

In the course of an investigation which has occupied much time during some years the writer has obtained a considerable number of definite compounds including silicon and the nitrogen of diverse organic groups in direct chemical union. Several of these new substances resemble in composition and in their general relations certain well-known compounds of carbon with nitrogen, such as amides, imides, and nitriles, among them being a silicocyanogen group, SiN, in combination. The formation of such substances afforded complete proof that silicon has, like carbon, though in less degree, a marked affinity for trivalent nitrogen, even when the latter is associated with complex organic groups. In the mineral kingdom no definite compounds of silicon with nitrogen have yet been met with; nor are they likely to be found at any part of the earth's surface to which water has easy access, as it is probable that any such substances would be very speedily decomposed in presence of moisture into silica and ammonia, or their derivatives. On the other hand, the existence of the great group of "alumino-silicates," which constitute so large a proportion of granitic and other similar rocks, affords clear evidence of the strong attraction of silicon for aluminium, which latter acts as an essentially trivalent element in its high temperature relations, and seems capable under such conditions of doing chemical work somewhat similar to the nitrogen. These considerations raised the question whether some at least of the alumino-silicated may not be regarded as fully oxidised products of silicides of trivalent aluminium, somewhat analogous to SiN, which had been formed at high temperatures in the first instance below the oxidised crust of the earth. It is evident that such "nuclear" silicides should be obtained for study by the complete deoxidation of the corresponding native silicates, or by direct synthesis from the sutiable elements. The first method was found to be impracticable in the most important cases, i. e. of alumino-silicates including alkali or alkaline earth metals. The application of the second or synthetic method has proved satisfactory, as it has led to the discovery of substance or remarkable stability, provisionally named Calcium Silicalcyanide, and with which a new synthesis of the felspar Anorthite has been effected. The results recorded in the following pages tend to support the view suggested above as to the nitrogen rôle of aluminium in certain silicides, and afford some further clues to the constitution and natural relations of the plagioclasic felspars.