IRON. 351 



pound of 1 atom sulphur and 1 atom iron ; and, 

 consequently, that an atom of iron weighs 3*5. 

 These observations apply only to protosulphuret 

 of iron formed artificially. The native protosul- 

 phuret, when dissolved in muriatic acid, always 

 deposites a little sulphur. Hence, it contains 

 either a small mixture of persulphuret of iron or 

 of sulphur. 



Now, it is possible to convert protosulphuret 

 of iron into neutral protosulphate of iron, by int P rot - 



* sulphate of 



careful digestion in a sufficient quantity of dilute iron. 

 nitric acid. Hence it follows, that the sulphur 

 and iron have the same ratio to each other in 

 protosulphuret and protosulphate of iron ; name- 

 ly, the ratio of 2 to 3'5. When 2 of sulphur are 

 converted into sulphuric acid, they become 5 ; 

 and when 3 '5 of iron are converted into pro- 

 toxide, they become 4%5, as is obvious from what 

 has been stated above. Hence it is clear, that 

 17'375 grains of protosulphate of iron must con- 

 tain exactly 4*5 grains of protoxide of iron ; as 

 the quantity of sulphuric acid has been shown to 

 be 5 grains. Thus the proportion of acid, oxide, 

 and water in 17*375 grains of protosulphate of 

 iron has been rigidly made out ; and the com- 

 ponent parts of the salt are as follows : 



1 atom sulphuric acid 5 



1 atom protoxide of iron 4-5 

 7 atoms water . 7-875 



17-375 



