24 Chemical Examination of American Minerals. 



Sulphuric acid, 20-000 



Alumina, 6-360 



Silica, 0-012 



Lime, 0-136 



Peroxide of iron, ----- 0*110 



Magnesia, 



Protoxide of manganese. 



Soda, 4-000 



Water, - - - - - - - 22-209 



0-423 



53-250 



As the sulphuric acid obtained is equivalent to exactly 



4 atoms, it is obvious that the bases which saturate the acid, 



must constitute also atomic quantities. Now 6-75 make 3 



atoms of alumina. The quantity actually found, was only 



6-36, or 0-39 less than the atomic quantity. But the lime, 



peroxide of iron, protoxide of manganese and magnesia, (if 



we admit that the 0-42 contained 0-12 of magnesia) are 



equivalent to 0-39 alumina. It is clear from this, that these 



bodies took the place of a little alumina in the alum, and that 



if the alum had been pure, the quantity of alumina in 53*25 



grains of it, would have been exactly 6-75 grains, or 3 atoms. 



Nor is there any reason to doubt that the soda would have 



been exactly 4, or 1 atom, had it been obtained without loss. 



Hence the constituents of the soda alum are, — 



4 atoms sulphuric acid, _ _ - _ 



3 atoms alumina, ----- 



1 atom soda, -----, 



20 atoms water, - - _ - _ 



Or, we may state it this way. 

 3 atoms sulphate of alumina, 

 1 atom sulphate of soda, 

 20 atoms of water, 



53-25 



