228 AN ANALYSIS 



chief ingredient in sea-water, though the quantity of it may be 

 affected by the changes which occur from the actions of some 

 of the other salts. 



A similar conclusion is to be drawn with regard to the Mu- 

 riate of Magnesia. Though the proportion of it may be affect- 

 ed by the changes which occur in the analytic operations, still, 

 from the quantity in which it is obtained, a considerable part 

 of it must originally exist. 



The principal difficulty is with regard to the sulphate of 

 magnesia, and the sulphate of soda. It has always been sup- 

 posed, that sulphate of magnesia is an ingredient in sea-water, 

 from its being procured by evaporation ; and it is possible that 

 it may be so. But it is just as possible, a priori, that sulphate 

 of soda may be the original ingredient, and that, during the 

 evaporation, the mutual action between it and muriate of mag- 

 nesia, is favoured by the concentration, whence portions of 

 both are decomposed, and corresponding quantities of sulphate 

 of magnesia and muriate of soda are formed. Nor is there any 

 thing connected with the mere results themselves, which proves 

 which of these views is just. 



If the appeal be made to experiment, it is sufficiently esta- 

 blished, that sulphate of magnesia may be formed by the action 

 of sulphate of soda on muriate of magnesia. When these two 

 salts are boiled together in solution, a double decomposition 

 takes place at least partially, and portions of sulphate of mag- 

 nesia and muriate of soda are formed. On the other hand, the 

 reverse combinations may also, according to circumstances, be 

 established. We have seen reason to conclude, that they are 

 so from the agency of alcohol ; and even in an aqueous solu- 

 tion, when certain proportions of the salts are used, they ap- 

 pear, under some circumstances, particularly that of a low tem- 

 perature, to take place to a certain extent. But still these 



facts 



