IS ANALYSIS OF CORUNDUM, AND OF 



Alkalis do not The alkalis have no immediate action upon filver; but 1 

 acl on filver; have bferved, that crucibles of this metal, after they have 



yet the crucibles * ' * 



become rather been a long time in ufe, become fomewhat more brittle than 



Jor^fe" 16 '^ they WCre before ' 



The fixed alkalis Potafh and foda have long been termed fixed alkalis ; and 



rife by mere j t j s ce rtain that, if we compare them with ammonia, they are 



more'readily *°* Bat fixed is an abfolute term, and cannot admit of de- 



thanfoda. grees. If potafh, fuch as we obtain from Mr. Berthollet's 



method of preparing it, be kept in fufion at a very ftrong heat, 



it may be totally volatilized. The vapour of the alkali may 



be perceived in the room ; and vegetable colours will undergo 



the change which is ufually produced by alkalis. Indeed, in 



preparing Mr. Berthotlet's potafh, the vapour of the alkali 



Water afiifts may be eafily perceived. Soda is not quite fo volatile ; though 

 their elevation. fflr fVom beJng fixed> j t appears a]{ ^ that a liule water in . 



creafes the volatility of both potafh and foda, as happens with 

 Potafh ufefully boracic acid. This volatility of potafh, has been advantage- 

 W a-h!n Cd ^ oufi ^ a PP lied of late t0 the art of bleaching. 



§ II. 



On the Affinities the Earths hare been fujypofed to have for each 



other, in the humid way. 



In the courfe of the foregoing analyfis, I had occafion to 



make fome further obfervations concerning a fubject upon 



which I had been formerly engaged, namely, on the affinities 



the earths have been fuppofed to have for each other, when 



held in folution by acid or alkaline menftrua. 



On the affinities J n the XXVIIIth volume of the Annates de Chimie, page 1 89, 



each h oth a er thS ^ publifhed a paper upon the analyfis of fome magnefianftones. 



Kiitorical fads. In this paper, I took notice of the following affinities of the 



earths for each other, namely, the affinity of alumina for mag- 



nefia, of alumina for lime, and of alumina for filica. In the 



XX XI ft volume, page 246, there is a memoir, by Guy ton de 



Guyton's expe- Morveau, upon a fimilar fubject ;* and he there reports fome 



nments. experiments of his own, by which he was induced to think, 



that the earths do really poflefs a chemical attraction for one 



another. Since that time, the affinity of the earths has been 



* He has taken no notice of any of the experiments contained in 

 my paper, 



received 



