140 CHEMISTRY OF NATURAL WATERS. [IX. 



water with carbonic acid, solutions were obtained holding in a 

 litre 2.3 grammes of carbonate of lime ; of which one half was 

 soon deposited, even when the solution was kept under a 

 pressure of several atmospheres. It would thus seem that 

 saline liquids favor this temporary solubility of the carbonate 

 of lime as bicarbonates. 



In all of the above experiments an excess of carbonic acid 

 was present, but this I have since found is not essential, since 

 supersaturated solutions may be obtained holding as much as 

 1.2 grammes of carbonate of lime, together with sulphate of 

 magnesium and chloride of calcium, in a litre of water, without 

 any excess of carbonic acid. The power of alkaline chlorides 

 and of chloride of calcium to prevent the precipitation of chlo- 

 ride of calcium by carbonate of soda has already been observed 

 by Storer (Dictionary of Solubilities, page 110). I have found 

 that the precipitate produced by the admixture of solutions of 

 these two salts is readily dissolved, when recent, by a solution 

 of chloride of calcium or of sulphate of magnesia; and thus 

 liquids may be prepared holding at the same time from 1.0 to 

 1.2 grammes of neutral carbonate of lime and 1.0 of neutral car- 

 bonate of magnesia, in presence of sulphate of magnesia. These 

 solutions of carbonate of lime, which are strongly alkaline, may 

 be kept for twelve hours or more without perceptible change 

 at ordinary temperatures, but after a time deposit crystals of 

 hydrated carbonate of lime. The addition of alcohol imme- 

 diately throws down the whole of the carbonate of lime in an 

 amorphous condition. 



The carbonate of magnesia is still more soluble than the 

 carbonate of lime under similar conditions, and it is possible to 

 obtain 5.0 grammes of neutral carbonate of magnesia dissolved 

 in a litre of water holding seven per cent of hydrated sulphate 

 of magnesia, without any excess of carbonic acid. These solu- 

 tions, which are strongly alkaline to test-papers, yield a precipi- 

 tate by heat, which redissolves on cooling. 



It is evident that the mingling of saline and alkaline waters 

 may give rise to solutions like those just described, and thus 

 explain apparent anomalies in the composition of certain saline 



