142 CHEMISTRY OF NATURAL WATERS. [IX. 



58. IRON, MANGANESE, ALUMINA, AND PHOSPHATES. None 

 of the waters of the four classes here described contain any 

 notable quantity of iron, yet this element is never wanting in 

 those waters which contain earthy carbonates. Whenever a 

 portion of one of these waters, or better the earthy precipitate 

 separated from it by boiling, is evaporated to dryness with an 

 excess of hydrochloric acid, the residue treated with acidulated 

 water yields a portion of silica, and the solution will then be 

 found to yield with ammonia a precipitate. This, which is 

 partially soluble in caustic alkalies, is often colorless, and will 

 be found to consist of alumina and peroxide of iron, with phos- 

 phoric acid and a trace of manganese, which latter metal is 

 seldom or never absent. The small quantity of alumina which 

 these waters contain appears not to be derived from suspended 

 argillaceous matters, 'but to be held in a state of solution. 

 The phosphates are generally present only in very small quan- 

 tities in these waters, for the reason pointed out in 5. The 

 largest amount which I have met with was in an alkaline 

 water of Class III. from Fitzroy ( 43), where it is equal to 

 .0124 of tribasic phosphate of soda in 1,000 parts of water. 



59. BROMIDES AND IODIDES. The chlorides in these an- 

 cient mineral waters are always accompanied by bromides and 

 iodides, but the proportion of the bromides to the chlorides 

 appears to be much less than in the waters of the modern 

 seas. According to Usiglio, 100 parts of the salts from the 

 Mediterranean contain 1.48 of bromide of sodium ; while ten 

 analyses by Yon Bibra of the waters of different oceans give 

 from 0.86 to 1.46, affording for 100 parts of salts a mean of 

 1.16 of bromide of sodium, equal to 1.04 parts of bromide 

 of magnesium. The waters of Whitby and Hallowell, on the 

 contrary, which are the richest in bromides of those described 

 in this paper, contain only 0.54 and 0.69 parts of bromide of 

 sodium in 100 parts of solid matters; while few of the saline 

 springs of the second class contain more than one half of this 

 proportion, and some of them very much less. 



With regard to the iodides in many of these waters, how- 

 ever, the case is very different. The waters of the modern 



