304 On the alleged conversion of Carbon into Silicon, 



nitric acid, the residuum was fused and then treated with hy- 

 drochloric acid, which left a trace of insoluble matter, proba- 

 bly silica, but which was so minute as not to affect a balance 

 sensible to TUvtf gr. ; this minute quantity was most probably 

 accidental, and very probably was derived from the iron tube 

 which was corroded. The weight of the residual chlorides, 

 when evaporated to dryness, was 104 grs., so that if we admit 

 that only one-seventh of the quantities originally employed 

 were tested for silica, we should have above 20 grs. of ferro- 

 cyanide of potassium submitted to this trial, which, according 

 to Dr. Brown (p. 245), should yield 3*6 grs. of silicic acid. — 

 (J.D. S.) 



Subsequently to these experiments, it was observed in two 

 or three instances, that when paracyanogen made from the bi- 

 cyanide of mercury was submitted to the blowpipe flame in 

 a tube of common flint-glass, closed at one end and drawn to 

 a capillary at the other, that gaseous matter was evolved, and 

 a small hole blown out at that end containing the paracyano- 

 gen, through which aperture the gas escaped, and invariably 

 burnt with the characteristic flame of cyanogen. — (R. H. B.) 



This experiment was followed by placing, in a tube of Bohe- 

 mian glass, having a bulb at one extremity, a small quantity 

 of paracyanogen, prepared by dissolving the dark-coloured 

 product which results from the spontaneous decomposition of 

 hydrocyanic acid in sulphuric acid, and precipitating by water, 

 well washing, anddrying at a temperatureof 260° to 300° Fahr., 

 and plugging up the opening of the tube with plaster of Paris. 

 After causing the blowpipe flame to play upon the bulb con- 

 taining the paracyanogen for a short time, a small hole was blown 

 out as before, and cyanogen continued to burn for some time. 



Some more paracyanogen, prepared in a similar manner, was 

 placed in a similar tube of Bohemian glass, but in this instance 

 the bulb was carefully coated with luting, the open extremity 

 plugged as before, and the apparatus carefully dried ; the 

 flame of the blowpipe was then applied to the bulb for nearly 

 half an hour without any aperture being made in it. When 

 the contents of the bulb were removed, they presented precisely 

 the appearance of precipitated peroxide of iron immediately 

 after ignition, viz. a dark black glistening aspect ; this residue, 

 when burnt in a platinum capsule, was entirely dissipated, lea- 

 ving no residue whatever.— (R. H. B.) 



The disengagement of cyanogen in the last experiment but 

 one is completely at variance with the statement of Dr. Brown 

 in his paper < On Paracyanogen,' p. 168, " that pure paracyano- 

 gen (precipitated by atmospheric moisture from the sulphuric 

 acid solution of the common product) does not afford the 



