DR T. THOMSON'S Analysis of some Minerals. 467 



By a careful analysis, I found that 53.25 grains of it could be 

 resolved into the following constituents. 



Sulphuric acid, 20.000 



Alumina, ..... . i^;, 6.360 



Soda, 4.000 



Water, 22.209 



Silica, 0.012 



Lime, -'}'. '-/' J; ;' : f ; ''V'vl * '"' 136 



Peroxide of iron, . . v' r: . 0.110 

 Protoxide of manganese, with 



a little magnesia, . . ";- 0.423 



53.250 



It will be observed that the sulphuric acid corresponds exact- 

 ly with four atoms. Hence it is probable, that the bases which 

 saturate this acid in the salt amount also to exactly four atoms. 

 Four constitutes an atom of soda. But the atom of alumina 

 being 2.25, three atoms of that earth will amount to 6.75 ; where- 

 as only 6.36 were found in the salt. There is, therefore, a defi- 

 ciency of 0.39 grains of alumina. But the lime, iron, and man- 

 ganese, (if the magnesia contained in it be reckoned 0.12), are 

 together exactly equivalent to 0.39 alumina. Thus, it appears, 

 that these substances replace a small portion of the alumina in 

 the salt. 22.209 approaches very nearly to twenty atoms of wa- 

 ter. We may, therefore, neglecting the minute quantity of silica, 

 lime, iron, manganese, and magnesia, consider the salt as com- 

 posed of 



4 atoms sulphuric acid, . . 20 

 3 atoms alumina, .... 6.75 



1 atom soda, 4.0 



20 atoms water, 22.5 



53.25 



VOL. XI. PAKT II. 3 N 



