CHRYSOLITE. 



which are contained in the precipitated sesquioxide of 

 iron, and must be separated from it as in Nos. 21 and 

 25. 



About 1.5 per cent, of water is also present as an 

 unessential constituent ; its quantity may be ascer- 

 tained by ignition in a covered crucible. 



In order to ascertain directly the relative amounts 

 of protoxide and sesquioxide of iron, the process de- 

 scribed in No. 24 must be followed. 



77. CHRYSOLITE (OLIVINE). 

 2 (MgO, FeO), Si0 2 . 



The very finely-powdered mineral is decomposed 

 by digestion with concentrated hydrochloric acid, the 

 mass dried upon the water-bath, moistened with con- 

 centrated hydrochloric acid, and, after some time, 

 mixed with water and filtered from the separated 

 silica. 



Small amounts of copper and tin, which are con- 

 tained in many specimens of olivine, are detected and 

 separated by mixing the solution with saturated sul- 

 phuretted hydrogen-water, until it smells strongly, 

 and allowing it to stand for some time in a closed 

 vessel. 



The solution filtered from the precipitate is concen- 

 trated by evaporation, some chlorate of potassa being 

 added to peroxidize the iron. 



The sesquioxide of iron may be precipitated by an 

 excess of ammonia, and the magnesia separated from 

 it by boiling the solution until all the free ammonia 

 is expelled, when the sesquioxide of iron remains, and 

 may be filtered off'. 



This filtrate contains, besides magnesia, a small quan- 

 tity of protoxide of manganese and protoxide of nickel, 



