442 DR T. THOMSON'S Analysis of some Minerals. 



but not gelatinous ; 20 grains being treated in this manner, left a 

 quantity of white siliceous matter, which, after ignition, weighed 

 5-535 grains. This matter being fused with twice its weight of 

 carbonate of soda, dissolved in muriatic acid, and treated in the 

 usual way, was found composed of, 



Silica, 4.861 



Peroxide of iron, . . . 0.290 

 Red oxide of manganese, 0.384 



5.535 



The muriatic solution was evaporated to dryness, and the 

 dry residue digested in water, acidulated with muriatic acid, till 

 every thing soluble was taken up. There remained undissolved 

 a quantity of silica, which weighed after ignition 1 .059 grains. 



Suspecting the presence of manganese in the muriatic acid 

 solution, I neutralized it with ammonia, and threw down the 

 iron (it had been peroxidized by digestion with nitric acid ), by 

 benzoate of ammonia. 



The benzoate of iron, after edulcoration and drying, was 

 burnt in an open crucible, and kept red hot till the iron was 

 brought into the state of peroxide. It weighed 1 4.95 grains, 

 equivalent to 13.46 grains of protoxide of iron. 



The residual liquid was mixed with an excess of carbonate 

 of soda, and boiled in a flask. Nothing was obtained except a 

 trace of alumina too small to be weighed. 



Thus the constituents of the mineral, by this analysis, are, 



Silica, 9.92 or 29.60 



Protoxide of iron, . . 13.460 67.30 



Peroxide of iron, v 1 . 0.290 1 .45 



Red oxide of manganese, 0.384 1 .92 



20.054 100.27 



