Dr. Fyfe's Elements of Chemistry. 53 



interest of iron and the simple acidifiable bodies are those with car- 

 bon, sulphur and cyanogen :" this last, however, we need hardly state, 

 is a compound of two simple acidifiable bodies. The protosulphuret 

 of iron is rather a scarce substance ; and yet Dr. F. states that it is 

 employed in the preparation of the sulphate of iron by exposure to air 

 and moisture : — now it is the persulphuret, which is a very plentiful 

 mineral, that is used for this purpose. 



Respecting the liquor Jerri alkalini of the London Pharmacopoeia 

 Dr. Fyfe has committed several mistakes. In the first place " It is" 

 not " much used j" secondly, the solution of carbonate of potash must 

 not be added to the solution of pernitrate of iron, but the latter to the 

 former. The following remarks show indeed that Dr. F. is equally 

 ignorant of the nature of the process, and of the product obtained by it. 

 "In the first part of the process, a pernitrate of iron, but with a large 

 excess of acid, is formed ; and in the second, this excess is merely 

 saturated by the alcaline solution, a part of the iron being precipitated 

 in the state of a carbonate, but which is instantly dissolved by the 

 nitric acid ; so that the product is a mixture of nitrates of iron and of 

 potass." Now as the acid solution is added to the alkaline one, in- 

 stead of the reverse as here stated, the precipitate formed is not dis- 

 solved by the nitric acid, but by the carbonate of potash j so that the 

 product is not a mixture of nitrates of iron and potash, but a solution 

 of carbonate 'of potash holding peroxide of iron in combination, and 

 mixed with nitrate of potash. That the solution contains no nitrate 

 of iron might almost have been learned from the name, absurd as it 

 is, which the London College have given to this preparation. It is 

 sufficiently ridiculous to speak of alkaline iron j but it would have been 

 worse than this to have bestowed a name denoting alkalinity, where 

 none was in existence. 



The sulphas ferri exsiccatus of the Edinburgh Pharmacopoeia is not 

 deprived of the whole of the water of crystallization $ it retains one 

 atom of water. According to Dr. Fyfe, colcothar is used " for making 

 razor-strops :" we supposed they had been made of wood and leather, 

 and merely covered with colcothar. When the carbonated alkalies 

 are employed to decompose sulphate of iron, the protocarbonate is 

 not converted into percarbonate by absorbing oxygen, no such com- 

 pound exists j — it becomes a mixture of protocarbonate and peroxide 

 of iron. " Permuriate [of iron] with the maximum oxid" cannot "be 

 prepared by dissolving that oxide or the carbonate in the acid :" it 

 must be "that oxide," for the carbonate contains protoxide : by the 

 bye, as permuriate with the maximum oxide is so particularly mentioned, 

 may we inquire whether there is any permuriate without it ? In the 

 London Pharmacopoeia it is not the red oxide of iron which is used for 

 preparing the iinctura ferri muriatis, but the ferri subcarbonas, which 

 is a mixture of protocarbonate and peroxide : the Edinburgh process 

 for the same preparation does not at first yield a protomuriate, for the 

 scales of iron employed are a mixture, perhaps a compound, of pro- 

 toxide and peroxide of iron. — There are several other statements re^ 

 specting the compounds of iron which we are precluded from noticing 



merely 



