1* 



ANALYSIS OF CORUNDUM, ANl> OF 



of prifmatlc 

 thallite j 



•f thallite In 

 tranfparent frag- 

 ments; 



Thallite in Prifms like the Tourmalin. 

 Silica m . 40 



Alumina • - -25 



Lime * - - 21,5 



Iron - - - - 11,5 



Lofs 2 



100,0. 



Thallite in Fragments, of a fine tranfparent Yellow Colour, 



of fibrolite of the 

 Chinefe corun- 

 dum; 



Silica 



Alumina 



Lime 



Iron 



Lofs 



Fibrolite accompanying 

 Silica 



Alumina - 

 Iron 

 Lofs 



42 

 - > - 25,5 



16 

 - 14 

 2,5 



100,0; 



the Matrix of Corundum from China, 



38 



- 46 

 13 



- 3 



of felfpar from 

 fand of Ceylon. 



Felfparfrom the Sand of Ceylon. 



Silica 

 Alumina 

 Lime 

 Iron - 

 Lofs 



10O. 



63,5 



20,5 



7 



1,5 

 2,5 



100,0. 



As the greater part of the above fubftances were fufible 

 cibles alonemuft without difficulty in potafh, I preferred ufing a filver crucible 

 to any other. It may be laid down as a general rule, with 

 refpecl to delicate experiments, that in the treatment of me- 

 tallic fubftances, we fliould not ufe metallic crucibles ; but, in 

 the treatment of earthy bodies, they alone are to be depended 

 upon. The eafily oxidizable metals cannot be employed ; but 

 filver and platina prefent advantages which no other metals 



feem 



be ufed with 

 earths ; 



namely, filver 

 and platina. 



