22 ANALYSIS OF CORUNDUM, &C. 



Alumina at- When a folution of potafh is boiled upon a mixture of lime 



which 'becomes anc * a,um » na » tne alumina is diflblved, together with a much 



diffblvcdin pot- greater portion of lime than can be attributed to the diflblving 



a& along with p 0V ver of the water alone. But, if a folution of potalh be 



boiled upon lime, without alumina, no more Hme is taken up 



than would have been diflblved by an equal quantity of water 



not containing potafh in folution ; confequently, alumina 



feems really to promote the folution of lime in potafh. The 



affinity of alumina for lime, I had mentioned in the paper to 



which I allude j and it has fmce been noticed by Mr. Vau- 



quelin *. 



Guyton's con- If the conclusions of Mr. Guyton had been well founded, it 



dufions, iftrue, wou j d h ave been chemically impoffible to arrive at truth in 



would have ren- ... 



dered analyfis anatyus. There were already real difficulties enough to be 

 uncertain. overcome j and Mr. Berthollet has lately difcovered fome, 



which are not fo eafily anfwered as thofe I have juft confi- 

 dered. The pofition of this chemift, however, has been too 

 Objection to generally extended by him. If the power of mattes were as 

 Berthollet*! un- g reat as j ie r eprefents it to be, and if it increafed ad infinitum, 



limited pofition ° '. l j » 



refpeaing at- in proportion to the mafs, it rauft follow, that, with any given 



traclion from fubftance, we could decompofe any compound, provided the 

 the mafs. _ _ * J / . x 



mals ot tne decompounding body were tumciently great ; but 



this is well known not to be the cafe. 



From the experiments which I have related, it appears to 



be proved, 



Recapitulation lx ^- That there exiils an affinity between filicaand alumina. 



of the affinities 2dly. That there exifts a very powerful affinity between 

 of the earths, 1 • , r 



&c> alumina and magnefia. 



3dly. That alumina fliews an affinity for lime ; but that the 

 faid affinity is not fo ftrong as Mr. Guyton had fuppofed, nor, 

 if pure reagents be ufed, is it to be perceived under the cir- 

 cumflances Mated by him. 



4thly. That Mr. Guyton was miftaken in every inftance of 

 affinity between the earths, excepting in the cafe of filica with 

 alumina, which had been obferved before his experiments ; 

 and that, in the other cafes, he has attributed to a caufe which 

 does not exifi, phenomena that muft have refulted from the 

 impurity of his reagents. 



# Scheele was, in fa£r, the firft who perceived this affinity. See 

 his EJfay on Silent Clay, and Alumina, 



5thly» 



