354 IRON, NICKEL, COBALT, &c. 



were reduced to a coarse powder, and digested 

 in dilute nitric acid till the whole was dissolved. 

 An excess of caustic ammonia was then poured 

 into the solution, by which the peroxide of iron 

 was thrown down. It was collected on a double 

 filter, washed, dried, and exposed to a red heat. 

 It weighed exactly 5 grains. The residual li- 

 quid, thus freed from iron, was concentrated, in 

 order to drive off the excess of ammonia. It 

 was then mixed with a sufficient quantity of mu- 

 riate of barytes to throw down all the sulphuric 

 acid. The sulphate of barytes, thus obtained, 

 being washed, dried, and heated to redness, 

 weighed 29*5 grains, equivalent to 4 grains of 

 sulphur. From this experiment it is evident, 

 that persulphuret of iron is composed of 



Sulphur 4 

 Iron 3-5 



7-5 



or two atoms sulphur and 1 atom iron. But 

 during the experiment the 3%5 of iron were con- 

 verted into peroxide, which weighed 5. Hence 

 it is obvious, that peroxide of iron is composed 

 of 



Iron 3' 5 or 1 atom 



Oxygen 1-5 - 1 atom 



