120 CHEMISTRY OF NATURAL WATERS. [IX. 



The nearly saturated brines from the Saginaw valley in 

 Michigan, which have their source at the base of the carbonifer- 

 ous series, contain, according to my calculation from an analysis 

 by Professor Dubois, in 100 parts of solid matters: chloride 

 of calcium 9.81, chloride of magnesium 7.61, sulphate of lime 

 2.20, the remainder being chiefly chloride of sodium. Another 

 brine in the same vicinity. gave to Chilton an amount of chloride 

 of calcium equal to 3.76 per cent.* In a specimen of salt man- 

 ufactured in this region, Goessmann found 1.09 of chloride of 

 calcium ; and in two specimens of salt from the brines of Ohio, 

 from the same geological horizon, 0.61 and 1.43 per cent of the 

 same chloride. The rock-salt from the lias of Cheshire, accord- 

 ing to Nicol, contains small cavities, partly filled with air, and 

 partly with a concentrated solution of chloride of magnesium, 

 with some chloride of calcium. t 



* Winchell, Amer. Jour. Sci. (2), XXXIV. 311. 



f Edin. Neu. Phil. Jour., VII. 111. The results of the analyses by Mr. 

 Northcote of the brines of Droitwich and Stoke in the same region (L. E. & D. 

 Philos. Mag. (4), IX. 32), as calculated by him, show no earthy chlorides what- 

 ever, and no carbonate of lime, but carbonates of soda and magnesia, and sul- 

 phates of soda and lime. He regarded the whole of the lime present in the 

 water as being in the form of sulphate. If, however, we replace, in calculating 

 these analyses, the carbonate of soda and sulphate of lime by sulphate of soda 

 and carbonate of lime, we shall have for the contents of these brines : chlo- 

 ride of sodium, with notable quantities of sulphate of soda, some sulphate of 

 lime, and carbonates both of lime and magnesia ; a composition which is more 

 in accordance with the admitted laws of chemical combinations. From these 

 results, it would appear that the earthy chlorides, which according to Nicol 

 are present in the rock-salt of this formation, are decomposed by sulphates in 

 the waters which, by dissolving it, give rise to the brines. 



It is to be regretted that in many water-analyses by chemists of note, the 

 results are so calculated as to represent the coexistence of incompatible salts. 

 Of the association of carbonates of soda and magnesia with sulphate of lime, 

 as in the analysis just noted, it might be said that I have shown that it 

 may occur in the presence of an excess of carbonic acid (ante, page 90). By 

 evaporation, however, such solutions regenerate carbonate of lime and sul- 

 phates of soda and magnesia; and by the consent of the best chemists these 

 elements are to be represented as thus combined. But what shall be said 

 when chloride of magnesium, carbonate of soda, and silicate of soda are given 

 as the constituents of a water whose recent analysis may be found in a late 

 number of the Chemical News ; or when bicarbonates of soda, magnesia, and 

 lime are represented as coexisting in a water with sulphates and chlorides of 

 magnesium and aluminum ? These errors probably arise from determining in 



