with Observations on the Analysis of Salt-lrines. 101 



In general, when muriate of lime and muriate of magnesia are 

 stated as ingredients with sulphate of lime, no sulphate of soda 

 or sulphate of magnesia is found. The reason is obvious, that 

 if either of these salts existed, it would react on the muriate of 

 lime, and form sulphate of lime. But when muriate of lime is 

 not found, sulphate of magnesia, or sulphate of soda, is often 

 stated as an ingredient, obviously owing to the circumstance, that, 

 although a portion of muriate of lime has been present, so as to 

 form sulphate of lime, there has not been a quantity sufficient. 

 to decompose the whole sulphate of soda, or sulphate of mag-.. 

 nesia. 



A striking example of these facts is to be found in Dr. Henrv's 

 analysis of the different varieties of sea- and rock-salt *. In four 

 varieties of rock-salt, tlierc were found small quantities of mu- 

 riates of lime and magnesia, vvith a portion of sulphate of lime, 

 hut no sulphate of magnesia ; while in the different varieties of 

 sea-.salt, British and foreign, there was no appreciable quantity, 

 and in some of them no trace whatever of muriate of lime, but 

 in all of them with sulphate of lime considerable quantities of 

 Milphate of magnesia. la the latter, therefore, the muriate of 

 lime had been converted entirely into sulphate of lime from the 

 excess of sulphate of magnesia; in the former, from the defi- 

 ciency of the sulphate, a portion of the muriate of lime had re- 

 mained undecomposed. 



A result somewhat siuiilar, and which affords a very direct ap- 

 plication of the same principles, is stated by Mr. Horner, in his 

 analysis of the salt-brine at Droitwich, compared with that of 

 Cheshire f. The latter contains a little muriate of lime; the 

 former contains none. But, then, that of Droitwich contains 

 Milphate of soda and sulph.ate of lime ; there is every probability, 

 therefore, that its muriate of lime has been converted into sul- 

 phate of lime by the sulphate of soda, which is in excess ; while 

 in the Cheshire brine, a> there is no sulphate of soda in excess, 

 that is, none after the evaporation, a portion of muriate tf lime 

 remains. 



There is a singular fact stated by Dr. Henry with regard to 

 what is called fishery salt, prepared from salt-brine, which seems 

 to admit of explanation only on these views. He found the pro- 

 portion of sulphate of lime mixed with it to be less, as it was col- 

 lected at a later period of the evaporation ; that drawn from the 

 boiler, after two hours application of the heat, contained in 1( 

 parts 16 of sulphate of lime; that after four hours contained 

 only 11 ; and that after six hours only 3|. Now if the water 

 of this brine held sulphate of lime in solution, the sulphate wou'd 

 begin to be deposited when the <iuantity of water was diminished 



• I'hilosophical TrnnsRcUoni, IrflO. f Geological Transactions, rol. ii. 



G3 to 



