on the alleged Conversion of Carbon into Silicon. 299 



hydrochloric acid was added in excess, which occasioned the 

 evolution of the characteristic odour of hydrocyanic acid; this 

 acid solution, evaporated to dryness, ignited to redness, and 

 treated with water, left a trace of reddish matter entirely so- 

 luble in hydrochloric acid. — (J. D. S.) 



Five grs. of paracyanogen were then mixed with about 40 

 grs. of dried borax, and exposed to a white heat for full two 

 hours in a platinum crucible, covered and placed in a Hessian- 

 luted crucible, as in the preceding experiment ; when with- 

 drawn, the Hessian crucible was completely glazed exteriorly, 

 and had evidently been softened by the heat ; in the platinum 

 crucible there remained a glassy substance of a light sea-green 

 colour; this, treated with water, gave an alkaline solution, which 

 precipitated lime-water and effervesced with hydrochloric acid, 

 evaporated the acid solution to dryness and fused the re- 

 sidue; again treated the residue with hydrochloric acid, and 

 after evaporation to dryness, fused ; the fused mass, treated 

 with distilled water and hydrochloric acid, left a slight sedi- 

 ment ; when this sediment was fused with carbonate of pot- 

 ash and the residue treated with hydrochloric acid, evaporated 

 to dryness and ignited, the ignited chloride of potassium was 

 wholly soluble, without any sediment whatever, in water aci- 

 dulated with hydrochloric acid ; the solution contained traces 

 of lime.— (J.D.S.) 



This experiment was repeated upon rather a smaller scale, 

 with precisely the same results. 



Notwithstanding the decisive nature of the experiments just 

 detailed, we determined, in order to avoid every objection, to 

 subject paracyanogen prepared from bicyanide of mercury — 

 the paracyanogen employed by Dr. Brown — to the process 

 indicated by him as simple and free from fallacy. Some bi- 

 cyanide of mercury was powdered and shaken down closely 

 in a porcelain crucible, which was then covered and firmly 

 luted ; this was placed in another crucible, also covered and 

 subjected to a full red heat for half an hour; the residue was 

 black and coherent ; a portion of this ignited left a trace of 

 oxide of iron, and it was almost entirely soluble in sulphuric 

 acid. 



Twenty grs. of this paracyanogen were mixed with 120 grs. 

 of carbonate of potash and ignited for one hour and a half at 

 a full yellow heat, the same precautions being taken as in the 

 experiment before cited ; when withdrawn, the residual salt 

 was white, soluble in distilled water, gave with mixed per- and 

 protosulphate of iron and hydrochloric acid a precipitate of 

 Prussian blue, and evolved much hydrocyanic acid on the 

 addition of hydrochloric acid, which occasioned no precipi 



