DR BROWN ON THE PRODUCTION OF SILICON FROM PARACYANOGEN. 239 



and, according to the foregoing experiment, 6.3 grs. of this were cyanogen, so that 

 4.29 grs. of nitrogen were driven away from 15- 6.3=8.7 grs. of paracyanogen. 

 The inference from these experiments is, that two equivalents of nitrogen are 

 thrown off from paracyanogen when it is changed into silicon and nitrogen ; that, 

 in other words, silicon is isomeric with carbon. This is only indirect evidence 

 that the silicon is derived solely from the carbon of the paracyanogen ; but I can- 

 not devise another method of determining the point, and it appears to be suffi- 

 ciently decisive. It may be added that the solid products of these experiments 

 were examined, and found to consist solely of platinum and silicon, the weights 

 of the latter, calculated from the silicic acid produced by it, being conformable 

 to the combining proportions of paracyanogen and carbon. 



In the repetition of these analyses, it must always be borne in mind that 

 different specimens of paracyanogen contain different proportions of condensed 

 cyanogen. One specimen yielded me more than 40 per cent. It depends partly 

 on the temperature at which it is formed, there being also less risk of appreciable 

 traces of silicon in the product the lower the temperature ; and partly on the 

 form of apparatus employed, or rather on the degree of pressure under which the 

 bicyanide is decomposed. Let a specimen be tested before it be analyzed : If 

 it be wholly soluble in concentrated sulphuric acid, it is fit for analysis, and the 

 quantity of cyanogen it contains will be discovered in the course of the operation. 



IV. On the production of the Siliciuretfrom the Paracyanide of Iron. 



The fourth part of the inquiry was devoted to the production of siliciuret of 

 iron from the paracyanide of the same metal ; and particular attention is solicited 

 to it, because the experiments are simple in design, infallible, and easy of execu- 

 tion on large quantities of material, while some of the products are as beautiful 

 as they are striking. The results, which have been obtained in the course of a 

 lengthened investigation, are embodied in the following formulae for the prepara- 

 tion of the siliciuret from the paracyanide, a method which is resorted to for the 

 sake of brevity 



It is necessary to premise, that the paracyanide of iron used in my experi- 

 ments was obtained from the ferrocyanide of potassium by the action of sulphur, in 

 the following manner : An equivalent proportion of well-dried ferrocyanide of po- 

 tassium, intimately mixed in powder with three equivalents of sublimed sulphur, 

 was heated six hours to the lowest glowing temperature of iron in the dark, in a 

 strong sealed tube, from which the access of air was prevented by drawing the open 

 end into a capillary. The product, having been quickly reduced to a fine powder 

 while yet warm and in a dry atmosphere, was introduced into a percolating tube 

 three feet in length, half an inch in diameter, and tapering at the dropping ex- 

 tremity to the width of a line. Linen having been bound over the dropping hole, 



