with Olservations on the Analysis of Sail-brines. 13 



evaporate sea-water to dryness ; during the evaporation, sul- 

 phate and carbonate of lime were precipitated, and were with- 

 drawn : the dry saline mass was lixiviated with alcohol ; and 

 the ley being poured off clear, was found to hold in solution mu- 

 riate of magnesia and muriate of lime ; the undissolved matter 

 was then heated, with a mixture of two parts of alcohol and 

 one of water, by which it was almost entirely dissolved ; it de- 

 posited, however, on cooling, a white powder, which was found 

 to be sulphate of soda, and sulphate of magnesia, and it retained 

 dissolved the muriate of soda of the sea-water with a portion 

 likewise of muriate of magnesia. 



Now a portion of sulphate of lime was obtained in this pro- 

 cess, which, according to the view I have stated, was probably 

 produced by the mutual decomposition of sulphate of soda and 

 muriate of lime. But it is also possible, that this decomposition 

 might not be complete. I had formerly found, indeed, that when 

 a liquor containing these two salts is evaporated, their decom- 

 position is not entirely effected* ; it spemed possible, therefore, 

 that portions of both might remain undecomposed in Lavoisier's 

 process ; the alcohol applied to the solid matter would remove 

 the muriate of lime, and thus the sulphate of soda would re- 

 main. To elucidate the whole subject, therefore, it seemed best 

 to repeat Lavoisier's analysis as he had performed it, and ascer- 

 tain the actual results. 



A. Four pints of sea-water of the Frith of Forth, taken up 

 near Leith, at a distance from any fresh water, were evaporated 

 by the heat of a sand bath ; the evaporation being continued 

 nntil a pellicle of salt formed on the boiling liquor. A preci- 

 pitate subsided during the boiling, which being washed, weighed 

 when dry 25 grains. 



B. The li([uor was -evaporated to dryness, and the saline mass 

 was dried thoroughly by a continued heat of about 150°; it 

 weighed 1025 grains. To separate the salts composing it, it 

 was submitted to the action of alcohol. About 4 ounces of al- 

 cohol of the specific gravity of 840 were poured upon it in a 

 bottle, and allowed to remain over it for 12 hours, being occa- 

 sionally agitated ; and when poured off an ounce of the same 

 alcohol was added, and after frequent agitation, and being kept 

 over it for some hours, was poured off, and added to the furmer. 



C. 'i'he residuum, when dried, weighed ^^90 grains ; 1.35 

 grains had therefore been abstracted, consisting chiefly of earthy 

 muriates. 



D. The saline matter was digested with 9 ounces of a weaker 

 spirit, composed of 2 of alcohol and 1 of v/ater, heat being ap- 

 plied to it by a sand-bath nearly to ebullition, with frequent 



* Transactions, vol. vii. p. 4/5. 



agitation ; 



