of Carbonic Acid in Mineral Waters. 51 



Wlien lie introduced into a graduated I'eceiver over mercury 

 containing eight cubic inclies of carbonic acid gas, a solution 

 of muriate of barytes previously mixed with half its weight of 

 caustic ammonia, an immediate absorption of 2.7 cubic inches 

 of gas took place, without disturbing the transparency of the 

 liquid. It did not begin to show a milky appearance until 

 after the mercury had risen higher and three cubic inches of 

 gas had disappeared. The eight cubic inches of gas were after- 

 wards absorbed entirely, and yet no considei able precipitate 

 took place. After the j^recipitate was separated by a filte.r, the 

 clear filtered liquid was heated to ebullition, by which means a 

 considerable quantity of carbonate of baryt was further sepa- 

 rated. 



A solution of muriate of lime with ammonia is acted upon 

 by cai'bonic acid gas in the same way as muriate of barytes. 

 After some hours of contact the liquid is hardly rendered tur- 

 bid, and even after 21 hours the filtered Hquid gives a preci- 

 pitate by ebullition. 



Only in cases where a great quantity of gas is absorbed by 

 the ammoniacal solutions of baryt and lime, or where the mix- 

 ture stands for several days, are the carbonates entirely preci- 

 pitated. 



In the absence of a mercurial apparatus in examining mineral 

 springs on the spot, lime water is sometimes employed, and 

 not altogether improperly, if the quantities of carbonic acid 

 gas are but small : I found, however, that lime water, even 

 when the lime is not entirely separated by the carbonic acid, 

 retains some carbonate of lime in solution, which will be found 

 by heating such lime water to ebullition, in a closed retoit, 

 when the carbonate of lime remaining in solution will fall to the 

 bottom. 



But this pha^nomenon ought not to be mistaken for, and 

 should not be considered as analogous to, that observed by Mr. 

 Dalton, when pure lime water was likewise rendered turbid 

 by ebullition ; for it has been ascertained since by Mr. Phillips 

 {Ann. de Chim. ct de Phij's. v. 16. 213.) that lime is much less 

 soluble in hot than in cold water. 



In order to convince himself that the precipitate obtained 

 was neither hydrate of lime nor crystallized lime. Dr. Vogel 

 made a comparative experiment by introducing into a given 

 quantity of newly prepared lime water carbonic acid gas in such 

 proportion that the lime water remained still alkaline; he fil- 

 tered, and heated it to ebullition in a long-neckod matrass, 

 by which it was rendered very turbid ; ho then .separated 

 the jirecipitale, which, on being dissolved in muriatic acid, 

 l)ioiluced a violent eflervcscence. 



O 2 An 



