VI 



ANALYSIS OF CORUNDUM, ANft ©F 



Imperfect Corundu?n from 

 China. 

 Silica 

 Alumina 

 Iron 

 Lofs - 



5,25 



86,50 



6,50 



1,75 



100,00. 



Jmperfeft Corundum from 

 At a. 

 Silica - 6,5 



Alumina - - 87,0 

 Iron ... 4,5 



Lofs --- 2,0 



100,0. 



As I could not difcover chrome, or any other colouring fub- 



Their difY. of 



from theoxi- ^ ance * except iron, in thefe ftones, I can attribute their differ- 

 dizemcnt of the ence of colour only to the different ftate of oxidizement of the 

 iron. j ron . ^ ut - lt j s j m p (jjb] e t afcertain what that ftate may be, 



from fo fmali a quantity. 

 The matrices of The matrices of thefe ftones, and the fubftances accompa- 

 mit to die ufu*l" n )' m g tnem > ar e more eafily fufed than the fix kinds of corun- 

 analyfis. dum juft mentioned. The ufual and well known mode of treat- 



ment by potafh, was fufficient to render thefe fubftances foluble 

 in the acids. Since the many experiments of Klaproth, Vau- 

 quelin, and others, the mode of analyzing mineral bodies fs 

 become fo familiar to chemifts, that I fhall mention particulars 

 with refpecl to one only of the following fubftances. 



MATRIX OF CORUNDUM FROM THE PENINSULA 

 OF INDIA. 



Matrix of Indian l . A certain quantity of this matrix was reduced to powder, 



ers^tufed with° m ^ e manner already defcribed. 1 00 grains of it were treated 



potato; diflblvedwith potafh, in a filver crucible : they then afforded a limpid 



»n mur. acid j folution in muriatic acid. The liquor was evaporated ; and, 



diflbl. in fm. ex- long before the mafs was entirely dry, it had affumed the 



cefs of acid ; left a ppe arance of a jelly. When the faline matter in the evapo- 



rating-difh was diflblved in a flight excefs of acid, a white 



powder remained at bottom, which had all the properties of 



filica, and, when wafhed and ignited, weighed 4-2,5 grains. 



Ammonia threw 2. Into the liquor which had ferved to wafh the above pow- 



down alumina ^^ j p 0urec j amm0 nia. A copious precipitate was thus formed, 



which was feparated by filtration, and well wafhed. 



3. Carbonate of potafh alfo caufed a precipitate in the li- 

 quor of No. 2. This precipitate was found to be carbonate of 

 lime, and weighed 23,5 grains, = 15 of lime. 



4. The precipitate of No. 2. was rediflblved in muriatic 

 acid ; then boiled with an excefs of potafh, and filtered. There 

 remained undiffolved, 3 grains, which were iron. 



5. The 



Carb. potafh 

 threw down 

 carb. lime ~ 

 Ttme 15. 



The alumina 

 and oxide were 

 diff. in mur. 

 acid j and the 



