150 GARXET. 



the excess of sulphuric acid, the bases remain as sul- 

 phates. 



The dry mass is moistened with concentrated sul- 

 phuric acid, and after a little time mixed with water, 

 in which, if the decomposition be complete,. it should 

 entirely dissolve. 



From this solution the alumina and alkalies are 

 separated as directed above. 



A small quantity of iron, which is frequently present, 

 is to.be sought in the alumina. 



In the analysis of a feldspar containing lime (labra- 

 rlorite, anorthite). the latter is precipitated, after the 

 separation of the alumina, by oxalate of ammonia. 



When petalite and spodumene are analyzed by the 

 above methods, a mixture of salts of soda and lithia is 

 obtained at last, and must be analyzed as in the case of 

 triphylline. 



III. Silicates are easily decomposed by acids, if 

 melted to a glass with a small quantity of precipitated 

 carbonate of lime in a platinum crucible before the 

 gas blowpipe. One part of feldspar is mixed with 

 0.4 parts of carbonate of lime. 



In order to find the amount of alkalies in silicates 

 not easily decomposed by acids, they are mixed with 

 five to six of carbonate of lime and about three-fourths 

 chloride of ammonium and ignited, when the alkali 

 may be extracted with water. 



81. PYROXENE, AMPHIBOLE, GARNET, IDOCRASE, 

 EP1DOTE. 



Silcates of CaO, MgO, FeO, MnO and Al 2 O r 



The very finely-powdered mineral must be decom- 

 posed by fusion with four parts of carbonate of 

 potassa and soda. 



