MINERAL WATERS OF DUNBLANE. 469 



may be a product of the operation, not an original ingredient. 

 The sulphuric acid may exist rather in the state of sulphate of 

 soda, and when, in the progress of the evaporation, the liquor 

 becomes concentrated, this salt may act on a portion of the 

 muriate of lime, and by mutual decomposition, form cor- 

 responding portions of muriate of soda, and sulphate of 

 lime. 



A question of this kind is not merely one of speculation, but 

 the solution of it may sometimes throw light on the proper- 

 ties of mineral waters, particularly on their powers of affecting 

 the living system. The present affords a very good example 

 of this. Sulphate of lime is a substance apparently inert. If 

 it exist, therefore, as such in the water, it can contribute no- 

 thing to its efficacy. But in the other state of combination 

 which is supposed, both the quantity of the muriate of lime, 

 the more active ingredient, will be greater, and the presence of 

 sulphate of soda will in part account for the purgative opera- 

 tion which the water exerts. 



There is no very direct, and perhaps no decisive experiment 

 by which this question may be determined ; for any method 

 which would cause the separation of either substance as a bina- 

 ry compound, may also be conceived to operate by causing its 

 formation. Thus, though sulphate of lime is obtained by eva- 

 poration, this is no proof of its prior existence, since the con- 

 centration of the solution might equally cause its formation, 

 by favouring the action of the sulphate of soda, if it exist, on 

 the muriate of lime. Its separation by a precipitant, by alko- 

 hol for example, even if it were obtained, is liable to the same 

 ambiguity; a certain degree of concentration of the watery so- 

 lution would be necessary for the effect, and the farther ope- 

 ration of the alkohol might be precisely on the same principle, 

 — diminishing the solvent power of the water, and thus aiding 



Vol. VII. P. II. S O the 



