$% tie fear ches on Alumine. 



compofcd only in part by carbonat of foda and potam, dn 

 illumine is obtained, which makes no fenfible effervefcence 

 with acids, though there was no effervefcence during its pre- 

 cipitation. I then thought that the water of the folution, 

 which mull: be a little diluted to produce no effervefcence, 

 might be alone fufficient to retain the carbonic acid. But 

 this quantity of water, compared with the volume of the car- 

 bonic acid which ought to refult from the decompofition of 

 the alkaline carbonat, could retain by its own affinity for the 

 carbonic acid only a very fmall part of that which remained 

 in the folution. May we not here fuppofe, agreeably to the 

 ideas of Berthollet refpetting affinities, that the alumine pre- 

 cipitated contributes by its mafs, conjointly with the acidi- 

 ferous folution and the alkali, to retain the carbonic acid ? 

 \\ r c (hall find hereafter that the carbonated water diffolves 

 alumine. But this folution, when filtered, feems alio to aban- 

 don its carbonic acid in the open air as eafily as pure carbon- 

 ated water. 



IX. I have already mentioned (II.) what Bergman ftates, 

 that when a folution of alumine is precipitated by alkaline 

 carbonats, there is formed in the liquor, when it has been 

 expofed feveral days to the free air and heat, an earthy de- 

 pofit, arifing from the expulfion of the carbonic acid which 

 held it in folution. I repeated this experiment with all the 

 alkalies fatu rated with carbonic acid, but I never could ob- 

 ferve any precipitation pofterior to that of the alumine by the 

 alkaline carbonat ; and I think it probable that the refult 

 Bergman obtained was becaufe his alumine was not pure, or 

 becaufe his alkalies, being imperfectly faturated with car- 

 bonic acid, had difTolved a fmall quantity of earth. Betides, 

 the precipitate I ought to have obtained would have been 

 a combination of alumine and alkaline carbonat. 



Being defirous to afcertain, by a more direct experiment 

 than the preceding, if carbonated water was capable of dif- 

 folvins; alumine, I put into two -necked bottles pure alumine 

 recently precipitated bv carbonat of ammonia, and ftill moift, 

 I diluted it with a great quantity of diftilled water: I caufed 

 to circulate for eight hours, into this mixture, a current of 

 carbonic acid gas, This water, when filtered, was fubjecled 

 to ebullition : it immediately became turbid and depofited 

 alumine, which potafh was able todiffolve. The carbonated 

 water of alumine became turbid alfo on being mixed with 

 fome drops of ammonia ; and, at laft, by the mere agitation 

 of the corked bottle, in which it was, when only half full. 



I collected two or three grains of the alumine, precipitated 

 from the carbonated water by means of its expofure to the air: 



y< i00 ': it 



