IX.] CHEMISTRY OF NATURAL WATERS. 145 



the deoxidizing power of organic matters, which reduce the 

 sulphates to sulphurets. These in their turn may be converted 

 into carbonates, the sulphur being separated either as sulphu- 

 retted hydrogen (giving rise by oxidation to free sulphur), or 

 as insoluble metallic sulphurets. This reducing action not only 

 decomposes the soluble sulphates of soda, lime, and magnesia, 

 but also, as has been pointed out in 57, may extend to sul- 

 phate of baryta, and thus sulphuret or carbonate of baryta be 

 formed. It is the action of these soluble baryta-salts which 

 constitutes the second mode of desulphatizing waters ; and this, 

 if we may judge from the frequence with which baryta-salts 

 occur in the saline waters in question, appears to have been 

 the most general process. 



It is a fact worthy of notice, that a saline spring at Sabre- 

 vois, in the province of Quebec, near Lake Champlain, which 

 holds both baryta and strontia in solution, is at the same time 

 slightly impregnated with sulphuretted hydrogen. Another 

 saline and sulphurous spring, which rises within ten feet of 

 this, contains, however, a portion of sulphates. (Geology of 

 Canada, page 542.) 



62. I am indebted to Professor Croft, of Toronto, for some 

 notes of a recent examination by himself of a saline of the first 

 class, which contains at the same time a soluble sulphuret. 

 This water, from a boring in Chatham, Ontario, at a depth of 

 600 feet, and about 236 feet below the summit of the Cornifer- 

 ous limestone, had a specific gravity of 1039.3, and yielded 

 for 1,000 parts about 51 of solid matters. It contained large 

 portions of chlorides of calcium and magnesium, with very 

 little sulphate, traces of carbonate, and no free carbonic acid. 

 The water, which gave an alkaline reaction with turmeric, was 

 greenish in color, very sulphurous to the taste, and yielded a 

 purple color with nitroprusside of sodium, and a black precipi- 

 tate of sulphuret with a solution of sulphate of iron. A cur- 

 rent of carbonic acid rendered the recent water opalescent, and 

 by exposure to the air it deposited sulphur.* 



* [ For further studies of waters of this class, see the Supplement to this 

 paper.] 



7 J 



