112 



ALUM 



As the Top rock contains a larger excess of iron pyrites than the Bottom, they are 

 mixed so as to diffuse the sulphuric acid equally. 



Erdmann has thus analysed his German specimens : 



Alumina 

 Silica, . 



Magnesia ... 

 Sulphur .... 

 Carbon .... 

 Protoxide of iron . 

 Oxide of manganese 

 Sulphate of protoxide of iron 

 ,, ,, alumina . 

 lime 



Shales from Freienwalde, Shales from Puzberg, 



by Klaproth. by Bergemann. 



. 16-000 ..... 10-80 

 .' 40-00 . '.'... 45-30 

 . 0-25 



. 2-85 . '. 3-94 



. 19-65 . '. . '. . 5-95 

 . 6-40 . . '. '. . 5-50 



. . '. '. '. 0'60 

 1-80 '. . 5-73 



'. '. '. '. . 1'20 

 1-50 1-71 



potash . . . 1*50 



Chloride of potassium . . 0*50 



Sulphuric acid ... 



Water 10-75 



loi-ao 



1-75 



0-35 



0-47 



16-50 



8970 



