ASH OF THE REFINING HEARTH. 205 



For the detection of most of the admixtures, it is 

 best to employ the black residue which is left on dis- 

 solving the iron in dilute sulphuric acid, and which can 

 easily be prepared in considerable quantity. It con- 

 tains silicic acid, carbon, carbide of iron, phosphide of 

 iron, arsenide of iron, compounds of chromium and 

 vanadium with iron, molybdenum, &c. 



The total amount of the carbon (phosphorus, 

 arsenic, chromium, &c. ?) in iron may be separated by 

 digesting the fine iron-filings with a solution of 

 chloride of copper, when all the uncornbined iron is 

 dissolved, and copper precipitated in its stead. When 

 the solution has been poured off, the precipitated metal 

 is digested, out of contact of air, with a neutral solution 

 of sesquichloride of iron which redissolves the metallic 

 copper. 



When this residue is digested with potassa, the 

 latter dissolves a newly formed brown humus-like 

 substance, together with phosphoric acid, arsenic acid, 

 and silicic acid. Almost the whole of the silicic acid 

 may be determined in this residue. 



It is yet to be ascertained whether this residue can 

 be analyzed by heating in chlorine-gas. 



109. ASH OF THE REFINING-HEARTH. 



Crystallized=8 FeO, Si0 2 . 



The analysis of pure crystals picked out of the mass 

 is simple and easy, since they consist essentially only 

 of protoxide of iron and silicic acid. They are finely 

 powdered, and treated with hydrochloric acid and some 

 concentrated nitric acid until they are completely gela- 

 tinized, the analysis being conducted as in the case of 

 Lievrite. The sesquioxide of iron obtained is calculated 

 as protoxide. 

 18 



