OF IRON. 323 



tosulphate of iron. Its constituents, according 

 to the analysis of Chenevix, are 



Arsenic acid 38 or 7'75 



Protoxide of iron 43 - 8 '77 

 Water . . 19 - 3-875 



100 



The last column gives the proportions of the 

 constituents, supposing the quantity of arsenic 

 acid to be 7'7^, or an atom. 8'77 approaches 

 very near 9, which is 2 atoms protoxide of iron ; 

 and 3-875 is very near 3*9375, or 3j atoms 

 water. The true constitution of the salt is pro- 

 bably 



1 atom arsenic acid . 7*75 



2 atoms protoxide of iron 9 



3 atoms water . . 3-375 



20-125 



6. Protacetate of iron. This salt was first Protace- 

 described many years ago by Sir Humphrey te 

 Davy, who gave an account of it in his Re- 

 searches. When iron, or sulphuret of iron is 

 dissolved in acetic acid, the solution has a light 

 green colour, and is transparent. I attempted 

 to filter this liquid to get rid of the undissolved 

 iron ; but the liquid absorbed oxygen from the 

 atmosphere with inconceivable rapidity, and 



X2 



