ANALYSIS OF MINERAL WATERS. 261 



or nearly impracticable, to assign the precise composition, and 

 the real proportions of the compound salts ; and hence the 

 necessity of employing the direct method of obtaining them. 



The present state of the science leads to other views. 



If the conclusion were just, that the salts obtained by eva- 

 poration, or any analogous process from a mineral water, are 

 its real ingredients, no doubt could remain of the superiority 

 of the direct method of analysis ; and even of the absolute ne- 

 cessity of employing it. But no illustrations, I believe, are re- 

 quired to prove, that this conclusion is not necessarily true. 

 The concentration by the evaporation, must, in many cases, 

 change the state of combination, and the salts obtained are 

 hence frequently products of the operation, not original ingre- 

 dients. Whether they are so or not, and what the real com- 

 position is, are to be determined on other grounds than on 

 their being actually obtained ; and no more information is 

 gained, therefore, with regard to that composition, by their be- 

 ing procured, than by their elements being discovered ; for 

 when these are known, and their quantities are determined, 

 we can, according to the principle from which the actual 

 modes of combination are inferred, whatever this may be, as- 

 sign with equal facility the quantities of the binary compounds 

 they form. 



The accuracy with which the proportions of the constituent 

 principles of the greater number of the compound salts are now 

 determined, enables us also to do this with as much precision, 

 as by obtaining the compounds themselves. And if any error 

 should exist in the estimation of these proportions, the prose- 

 cution of these researches could not fail soon to discover it. 



The mode of determining the composition of a mineral wa- 

 ter, by discovering the acids and bases which it contains, ad- 

 mits, in general, of greater facility of execution, and more ac- 

 curacy, 



