on the alleged Conversion of Carbon into Silicon. 2Y 



" 3'04 grs. of silicic acid were extracted from 5 grs. of para- 

 cyanide of iron." The term extraction here, we presume, 

 has reference to the conversion of the carbon of the ferru- 

 ginous compound into silicon, and subsequently into silicic 

 acid by the action of carbonate of potash. Dr. Brown states, at 

 p. 240 of the Transactions, " That the substance in question, 

 viz. paracyanide of iron, contains nitrogen, carbon and iron, 

 in the ratios of 1, 2 and 1." We suppose these numbers re- 

 present the atoms of the respective substances ; 5 grs. of para- 

 cyanide of iron would therefore contain I'lll of carbon, for 

 54':12;:5:1*]11. Now taking the atom of silicon at one- 

 third of Berzelius's atom, in order to make silicic acid an 

 equi-atomic compound of silicon and oxygen, we shall have 

 22-22 -4- 3 = 7-406, and 7-406 : 15-406 :: J-lll : 2-3; so 

 that all the silica which could have been procured by the 

 transformation of the whole of the carbon in 5 grs. of para- 

 cyanide of iron, would have amounted to 2*3 grs. instead of 

 3*04 grs., as stated in the original memoir. We do not know 

 whether the excess of silica in this case was obtained by a 

 transformative force exercised upon iron or nitrogen, or both ; 

 but we cannot conceive that the carbon could have furnished 

 it; if so, Dr. Brown has even surpassed the transformative 

 power of nature. In another experiment, however, of Dr. 

 Brown's, the quantity of silicic acid falls amazingly short of 

 the calculated proportions, supposing the alleged conversion 

 to have been full and perfect. Thus it is stated at p. 245 of 

 the Transactions, that 5-4 grs. of silicic acid were obtained 

 from 30 grs. of ferrocyanide of potassium : now supposing the 

 ferrocyanide to have been anhydrous and the conversion of 

 all its carbon effected, there ought to have been obtained 

 12*06 grs. of silicic acid ; for the quantity of carbon in 30 grs. 

 of anhydrous ferrocyanide of potassium is 5-8 grs., therefore 

 7-406 : 15-406 : : 5-8 : 12-06. Doubtless Dr. Brown considers 

 the transformation in the experiment last referred to as being 

 very far from full and perfect; and we confess we are quite 

 astonished that he should have obtained as much silicic acid 

 as stated in his memoir. If the alleged conversion were ad- 

 mitted, of course, quoad carbon alone, for sake of argument,as 

 possible, it appears somewhat remarkable that two experi- 

 ments similar in j^rinciplc should have been so discordant in 

 result; and we cannot but think, that asserting that 3-04 grs 

 of one substance can be procured from a given weight of a 

 second substance only capable of yielding 2*3 grs., is very 

 like a " plenary mistake" 



The experiment on ferrocyanide of potassium, in p. 301 of 

 the Phil. Mag., October, is alleged to be " original on the 



