PROCESSES FOR THE CONVERSION OF CARBON INTO SILICON. 559 



mained of insoluble matter, which was found to be carbon, 0*4 = 0'88 gr. cya- 

 nogen, making together 1'74 gr. of the original weight of paracyanogen.* 



This possibility of paracyanogen passing back into cyanogen, strikes at the 

 root of all the processes with paracyanogen, cyanides, ferrocyanides, &c., where 

 fusion with an alkali is prescribed ; and explains the uniform appearance of hydro- 

 cyanic acid, when acids were added to the products of fusion. So long as much of 

 the carbon and nitrogen of the paracyanogen is spent in forming cyanide of potas- 

 sium, quantitative proofs of the conversion of carbon into silicon, even should it 

 occur, cannot be secured by any fusion process. 



Whether or not this remark applies also to paracyanogen heated alone we 

 cannot decide. By simply heating it, we have never been able to resolve it en- 

 tirely into cyanogen, nor, so far as we know, has any chemist. But it may resolve 

 itself into nitrogen and carbon, which would as effectually interfere with the end 

 in view. 



* This fact has been already noticed by Professor JOHNSTON, Transactions of the Royal Soc. of 

 Edinburgh, vol. xiv. p. 37 ; and by Messrs SMITH and BRETT, London and Edinburgh Philosophical 

 Magazine, vol. xx. p. 29 ; but we have mentioned our experiment particularly, because it was made 

 with paracyanogen purified in the way already mentioned, and the quantity of cyanide of silver produced 

 was ascertained. 



VOL. XV. PART IV. 7 M 



