1 02 An Analysis of Sea-water ; &c. 



to that extent that it was luiable to retain the wliole dissolved ; 

 and, HI the progress of the evaporation, would continue to be 

 deposited proportional to this, to -the end of it, and the muriate 

 ot soda would be deposited in the same manner ; so that the oro- 

 portion between the two would continue nearly the same. 'But 

 .If the sulphate of lime did not exist in solution, but derives its 

 -OTiiJU-i trom the action of sulphate of soda on muriate of lime, 

 which thcjse brines contain, this action would take place, when 

 a certain degree of concentration of the liquor had been at- 

 tained ; the *nl;^h&te of lime would then be copiously deposited ; 

 Jut as the evaporation continued to proceed, its quantity would 

 be diminished, as the quantity either of sulphate of soda, or of 

 muriate of lime, became less ; and its deposition would cease 

 when either of these salts was exhausted. 



This is placed in a still clearer light, by an analysis of these 

 brines, after evaporation, to a certain extent, compared with their 

 original composition. A brine from Northwich was found by 

 Dr. Henry to afford, by evaporation, saline matter, which, he 

 inferred, contained in lOOO parts, muriate of lime and muriate 

 of magnesia in nearly equal proportions 5 parts, sulpiiate of lime 

 19 parts, muriate of soda 974 parts. But the brine remaining 

 after the separation of all the common salt, which it is thought 

 worth while to extract, afforded saline matter by evaporation, 

 which he found to contain, in 1000 parts, muriate of magnesia 

 35, muriate of lime 32, sulphate of lime 6, muriate of soda 927. 

 Here, in the progress of the evaporation, the quantity of sulphate 

 of soda, which may be considered as an original ingredient of 

 the brine, had been diminished by the decomposition arising 

 from its action on the muriate of lime. The liquor, therefore, 

 after this, afforded by further evaporation, along with a large 

 quantity of muriate of lime, a small quantity only of sulphate of 

 lime; while, if this sulphate had been an original ingredient, it 

 would have continued to be afforded at least in equal propor- 

 tion. 



Something similar to this occurs in the evaporation of sea- 

 water. It is after a certain extent of evaporation, but while a 

 large portion of liquor still remains, that the precipit.ition of sul- 

 phate of lime takes place ; that is, after the concentration is suf- 

 ficient to favour the mutual action of the sulphate of soda, or 

 sulphate of magnesia, and muriate of lime. After this, the quan- 

 tity diminishes as the evaporation proceeds, till at last not a trace 

 of it, or of sulphate of lime, remains in the bittern, which con- 

 sists of muriate of soda, muriate of magnesia, and sulphate of 

 iTKignesia alone. This curious fact has not been particularly 

 noticed, though it is in consequence of it that magnesia is pre- 

 pared from bittern on the large scale, perfectly pure. 



All 



