230 DR BROWN ON THE PRODUCTION OF SILICON FROM PARACYANOGEN. 



parated from paracyanogen, when it is changed into nitrogen and silicon ; the 

 fourth contains processes for the preparation of amorphous, semicrystalline and 

 crystallized disiliciurets of iron from the paracyanide of iron and the ferrocyanide 

 of potassium ; and the fifth gives an easy process for the preparation of silicic 

 acid, on any scale of operation, by the reaction of the ferrocyanide of potassium 

 on the carbonate of potassa. 



I. On the Decomposition of Paracyanogen by Heat, out of contact with the Air or 

 with any Body possessed of a stronger attraction for Carbon than for Silicon. 



The following experiments Avere performed on paracyanogen procured by a 

 process implying the same principle as was inculcated in the Memoir already re- 

 ferred to, but with a somewhat diiferent and better apparatus. 



A B is a tube-shaped bottle of hammered iron, six or seven inches r 

 long, about an inch and a half in diameter, and furnished with a female I 

 screw at the mouth. C D is a screwing stopper, adapted to A, and 

 perforated from top to bottom by a canal a line and a half in diameter. 

 The bottle is filled with bicyanide of mercury, pressed down with a ram- 

 rod and hammer. The perforation having been stuffed with stucco, the 

 stopper is screwed firmly in, and the closed apparatus is laid on the sur- 

 face of a coke fire kept at a very low red heat. Mercurial vapour soon 

 begins to stream through the pores of the gypsum ; no purple flame ever 

 appears, and if the tube be suddenly snatched from the fire, there is not 

 observed any odour of cyanogen at the stopper. As soon as the appear- 

 ance of mercury has ceased, the apparatus is removed, and there is ob- 

 tained a full bulk of paracyanogen, of very nearly the same weight as the salt 

 contained of cyanogen. This is not, however, a case of the plenary transforma- 

 tion of cyanogen into paracyanogen ; for, as has been already noticed in my paper 

 on paracyanogen, the former substance is largely absorbed by the latter. The pro- 

 duct is paracyanogen as much impregnated with cyanogen as possible at the tem- 

 perature and under the pressure of the shut vessel in which it is produced. It 

 must be removed by clearing out the tube with whalebone or a feather ; for it is 

 not readily dislodged by agitation, and harder substances are apt to bring out traces 

 of iron, unless the operation of ignition have been conducted with great care. 



1. A quantity of paracyanogen was introduced into a small tube of common 

 glass, and the open end drawn into a fine capillary. It was fused, although with 

 difficulty, into a thick paste, by the highest heat procured from a large gas-flame 

 by the blowpipe ; care having been taken to handle the tube so as to prevent the 

 liquefaction and dropping of the glass. The semiliquefied matter moved about 

 in the tube, spreading itself over the sides, shrinking from the fire, and rapidly 



