PROCESSES FOR THE CONVERSION OF CARBON INTO SILICON. 553 



a parcel of carbonate of potass was employed which had not been tested. This 

 remark applies to a single experiment, all the others having been made with car- 

 bonate of certified purity. 



Encouraged by our success, comparative as it was, with the ferrocyanide of 

 copper, and anxious to procure quantitative results as to the amount of silica 

 yielded, we recently prepared several ounces of this salt, and washed and dried it, 

 with great care. On fusing it with carbonate of soda, however, we obtained only 

 traces of silica. Four specimens of the ferrocyanide were employed, two prepared 

 from ferrocyanide of potassium and sulphate of copper, and two from the former 

 salt and the nitrate of copper. All were washed and dried, and otherwise pre- 

 pared in the same way, and with the same care. 



The following are the quantitative results we obtained : 



Ferrocyanide of Copper (from Nitrate), grs. 318-7, fused with Bicarbonate of Soda, grs. 1200; gave of Silica, gr. 0-3. 

 Do. do. 325-5 do. 1200 do. 1-3. 



Do. (from Sulphate), 303.5 do. 1200 do. 1-0. 



Do. do. 280-6 do. 1000 do. 1-3. 



Do. do. 100- do. 200 do. 0-7. 



From 1328-3 grains of ferrocyanide of copper, we thus obtained only 4-6 grains 

 of silica. 



The last experiments we have to record, are those performed with paracyano- 

 gen. The paracyanogen employed was prepared by heating the cyanide of mer- 

 cury in iron tubes closed by screw stoppers, according to the process described by 

 Dr BROWN in his paper in the Society's Transactions for 1840.* 



Paracyanogen prepared in this way, when freed from the cyanogen which, 

 according to his view, was mechanically condensed in it, was found by him to be 

 entirely converted into silicon and nitrogen by different modes of treatment. The 

 simplest of all these was to heat the paracyanogen alone out of contact with air, 

 when its nitrogen passed away in the gaseous form, and its carbon became sili- 

 con. In two remarkable experiments recorded by Dr BROWN,| paracyanogen was 

 found to give off a weight of nitrogen less by 8 per cent, than it should have given ; 

 and the weight of silicon left behind was " conformable to the combining propor- 

 tions of paracyanogen and carbon." 



Satisfied that, could we shew a weight of silicon equivalent to that of the car- 

 bon, and one of nitrogen only 8 per cent, less than it should by calculation have 

 been, we should convince every chemist of the exceeding probability, if not the ab- 

 solute truth of the proposition, that carbon is transmutable into silicon, we carefully 

 repeated this experiment some ten or twelve times. 



We were foiled, however, on the very threshold, by finding that paracyanogen 

 when heated alone, instead of yielding only cyanogen and nitrogen, as it had done 

 to Dr BROWN, gave off also carbonic acid and carbonic oxide. 



f Transactions of the Royal Society of Edinburgh, vol. xv. p. 174. t Ibid. pp. 238, 239. 



