THE ACCOMPANYING SUBSTANCES. Q 



be fit for analyfis. From all thefe experiments I concluded, 

 that fome more efficacious mode of rendering corundum foluble 

 in acids was to be fought. 



I boiled a great quantity of fulphuric acid upon very finely Neither the vo- 

 powdered corundum in a platina crucible. But, although the ^ p^'AJ^ 

 acid, after a great length of time, had diilblved a little of the have any notable 

 ftone, I did not find this method more fatisfaftory than the *^ on on corun - 

 others. Nitric, muriatic, and nitro-muriatic acids, were lefs 

 effectual than the fulphuric. Phofphoric acid, held in fufion 

 with corundum, did not diffolve any notable portion of that 

 Hone, or render it foluble in other acids. 



I then had recourfe to fub-borate of foda (borax), which I Borax hfes it 

 found to anfwer beyond my expectation. Two parts of that f ca "| c< ^olax* 

 fait, calcined, and one of corundum, enter into fufion, at a and one of cor. 

 temperature which I judged to be about 80° of Wedgwood *; f°™ tnmwhUc 

 and a glafs, more or lefs coloured, is formed. This glafs is acid. 

 foluble in muriatic acid j and, by this method, it is eafy to ob- 

 tain a complete folution of corundum. My general method of 

 operating was as follows : 



I took one hundred grains of corundum ; and, having feve- Analyfis. ioo 



ral times made it red-hot, and plunged it into cold water, I put pulverized- fufed 



it into the fteel mortar, and treated it as already mentioned. I with 200 borax j 



then poured fome very dilute muriatic acid upon it, to wafli orT r - at ; ) c v a 3 c j ( J n . mu ~ 



whatever iron might have adhered, in confequence of its me-(evap. todrynefc 



chanical action upon the mortar. After it was dried and ° r • f* or ), 

 r precip. by alk. 



weighed, I put it into the agate mortar, and ground it as fine carbonate ; ab- 

 as I could. The augmentation of weight was then noted ; andjj ra ^ the lalts . 

 was always taken into account in the general refult. I then foive the precip" 

 put the whole into a platina crucible, with 200 grains of cal- in mur - acid ^ 

 cined fub-borate of foda, and expofed the mixture for an hour filter the mur!' 

 or two to a violent heat. When the crucible was cool, muriatic folution J precip. 

 acid was boiled upon it and its contents ; and, in about twelve ^j^ irf>«*rii - 

 hours, all the glafs difappeared. If I wiilied to obtain the filica oxide of iron is' 

 direaiy, I evaporated the whole to drynefs ; but, if other wife, KeTbut^lu" 

 I precipitated by an alkaline carbonate, and warned the preci- mina taken up 

 pitate, in order to get rid of all the falts contained in the liquor. by the allc * » 

 This latter mode I believe to be preferable. I then re-dilfolvedmina by mur. U of 

 the precipitate in muriatic acid, and evaporated for filica. But, an)m : VVafh, 

 as corundum contains only a fmall portion of this earth, there weigh^earths. 



* I have no doubt that a lower temperature would be fufficient. 



was 



