ON THE COMPOSITION OF EMERYi * 53 



- Mr. Klaprorh obtained from the Chinefe corundum, after proved nearly 

 fepai ating from it the particles which were attraded by the ^f^chinefe 

 magnet, corundum. 



Argillaceous earth - - - 84* 



Silex - - - - 6,5 



Iron - - . - 7,5 



98. 

 As this analyfis was no doubt conducted with greater care 

 than mine, tke lofs of weight was lefs ; but the proportion of 

 the ingredients is fufficiently near to {how that the fubftances 

 are effentially the fame. 



From 25 grains of emery which appeared the moll impreg- Other emery 

 pated with iron, and yet retained its ufual hardnefs, I obtained, JSSwSCL 

 argillaceous earth 12,5, filex 2, iron 8, and one grain was not 

 duTolved ; or, per cent. 



Argillaceous earth - - 50 



Silex 8 



Iron 32 



Undiflblved • - - 4 



94. 



-As fuch emery can eafily be had of uniform quality in large 

 pieces, I procured the powder employed in this experiment, 

 by rubbing two pieces againft each other. 



From 25 grains of emery, fimilar in appearance to the pre- Another ana- 

 ceding, but which had been digefted with marine acid pre- y '* 

 vious to the action of the alkali, I had. 



23,7 94,8. 



The hardnefs of emery, as far as I could judge by its cut- Emery appear* 

 ting rock cryftai and flint, appeared to be equal to that ofJJ^. a a ^ dia " 

 diamond fpar. The latter could not be fcratched by the 

 former; but, as emery has not a furface fufficiently polifhed 

 to render a mark vifible, the converfe of this could not be 



tried. 



All 



