Rrfearches on Alumine* 33 



it produced no efiervefeence by diflblving in acids, even when 

 I made the proof, before it was completely dried at the tem- 

 perature of the atmofphere. The cafe is the fame with the 

 al u*i me deposited at the bottom of bottles in which the car- 

 bonic acid gas had circulated. 



X. Bergman* then, had reafon to announce that alumine, 

 carbonic acid, and water, can enter into combination, though 

 the experiments on which he founded his aifertion do not 

 appear to me proper for proving it ; but he ought not to have 

 admitted, that alumine with carbonic acid formed a concrete 

 carbonate. 



On the other hand, Gren had fome reafon for faying that 

 alumine, preeipitated from its folutions by alkaline carbonates, 

 did not prefent itfelf in the form of carbonate of alumine. But 

 he 'ought. not to have inferred that alumine hni no affinity 

 for carbonic acid, (incc we have feen that carbonated water 

 diifolves that earth. Under thefe two points of view, both 

 thefe chemifts feem to have been deceived, though with op- 

 pofite fentiments, as too often happens when a particular 

 truth is given out as a oeneral truth. 



Of Native Carbonates of sllumine. 



XT. Hitherto I have examined only thofe aluminous car- 

 bonates confidcred as the production of art. It now remains 

 for me to fpeak of thofe which are confidered as natural. 

 [ (hall not examine whether the carbonic acid forms com- 

 pound or ternary combinations with alumine and another 

 earth or a metallic oxide. There is no need to fay, that be- 

 eaufe thefe combinations exift, we ought to conclude that the 

 carbonic acid forms with alumine a concrete carbonate. 

 Bergman infers that the latter compound exifts in nature, 

 becauie the argil of Cologne, expofed to a ftrong heat, gave 

 him feveral times its volume of carbonic acid gas. If we put 

 out of confideration the ternary or quaternary combinations 

 in which the argil of Cologne may be found, fiace it con- 

 tains the half Or the fourth of its weight of fubftances foreign 

 to alumine, the eonclulion of Bergman would be juft, if it 

 were certain that its earth contained no vegetable or animal 

 matter. But as the greater part of the argils found at the 

 uirfacc of the earth contain fome, and as they detonate (lightly 

 with nitre, little credit can be given to the observation of 

 Bergman ; efpecially as he adds, that the carbonic acid <{as 

 he obtained was mixed with hydrogen gas, which feems to 

 announce here the decomposition of fome vegetable or ani- 

 mal matter, or of water prefent with carbon in this argil *, 

 t Sec Home's frinc-iplts of Agriculture ^ . 1 aion. 



Vol. X. C ' There 



