226 AN ANALYSIS 



Lavoisier had stated muriate of lime as having been obtain- 

 ed in his analysis, being dissolved with the muriate of mao-ne- 

 sia in the alcohol with which the solid matter obtained by eva- 

 poration had been lixiviated. I found no trace of it ; and its 

 presence after the evaporation to dryness, does not seem com- 

 patible with that of either sulphate of soda, or of magnesia. 

 Yet if the preceding reasoning be just, it is possible that alco- 

 hol, by its solvent action, might cause its reproduction to a 

 certain extent from sulphate of lime. On the other hand, the 

 entire insolubility of sulphate of lime in alcohol, might prevent 

 it from being acted on ; this is even more probable ; and the 

 result stated of muriate of lime being obtained, is therefore, in 

 all probability, to be ascribed to error, principally perhaps to 

 its not being distinguished sufficiently from muriate of magne- 

 sia, the quantity of which is stated by Lavoisier evidently too 

 low. 



The 



of magnesia re-acting, and being converted into sulphate of soda and muriate of 

 magnesia. This singular case is evidently owing to the relation of the solubili- 

 ty of these salts to temperature. Muriate of soda has its solubility little increa- 

 sed by heat, of course little diminished by cold ; sulphate of soda is in this re- 

 spect precisely the reverse ; hence, at an elevated temperature, muriate of soda 

 is the less soluble salt; and this determines its formation and separation from a 

 compound solution, containing its elements ; at a low temperature, again, sul- 

 phate of soda is the less soluble salt ; and this equally determines its forma- 

 tion, of course occasions the reverse decompositions. Now, according to the 

 proportion of saline ingredients, and according to the state of concentration, 

 and the temperature favouring the tendency of certain salts to crystallization 

 more than others; it is easy to conceive, that in a compound solution, different 

 combinations may be established, as these circumstances vary, and thus products 

 may be obtained, under certain conditions, which are not obtained under others. 

 Although sulphate of magnesia, therefore, is usually obtained by evaporation 

 from sea-water, sulphate of soda, at some stages of the operation or under pecu- 

 liar circumstances, with regard either to relative quantity of the elements, or to 

 temperature, may likewise be formed. 



