SPRINGS, RIVERS, CANALS, LAKES, 



as the foregoing. Su'phat of silver being more soluble than the 

 muriat of the same metal, distilled water may be successfully used 

 to separate these salts. Muriat of silver is known by its fixity, 

 its fusibility, and especially in its being less easily decomposed than 

 sulphat of silver. This last, placed on hot coals, emits a sulphure- 

 ous smell, and leaves an oxyd of silver, which may be fused with- 

 out addition. 



The Examination of the Mineral Waters by Distillation. 

 Distillation is used in the analysis of waters, to ascertain the 

 gaseous substances they may be united to. These substances are 

 either air, more or less pure, or carbonic acid, or sulphurated 

 hydrogen gas. To ascertain their nature and quantity, some 

 pounds of the mineral water must be poured into a retort, suf- 

 ficiently large to contain it, without being filled more than half or 

 two-thirds of its capacity ; to this vessel a recurved tube is to be 

 adapted, which passes beneath an inverted vessel filled with 

 mercury. In this disposition of the apparatus, the retort must be 

 heated till the water perfectly boils, or till no more elastic fluid 

 passes over. When the operation is finished, the quantity of air 

 contained in the empty space of the retort must be subtracted from 

 the bulk of the gas obtained; the rest consists of aeriform fluid 

 which was contained in the mineral water, whose properties may 

 quickly be knovii by the proofs of a lighted taper, tincture of 

 turnsole, and lime water; if it catches fire, and has a foetid smell, 

 it is sulphurated hydrogen gas ; if it extinguishes the taper, 

 reddens turnsole, and precipitates lime water, it is the carbonic 

 acid; lastly, if ii maintains combustion without taking fire, is with- 

 out smell, and alters neither turnsole nor lime water, it is atmo. 

 spheric air. It may happen that thi* fluid may be purer than the 

 air of the atmosphere : in this case its degrees of purity may be 

 judged by the manner in which it maintains combustion, or by 

 mixing it with nitrous or hydrogen gas, in the eudiometers of 

 Fonlana and Volta. The process used in obtaining gaseous matters 

 contained in waters is entirely modern. A moistened bladder was 

 formerly used, which was adapted to the neck of a bottle filled with 

 mineral water: the fluid was agitated, and by the swelling of the 

 bladder, an estimate was made of the quantity of gas contained in 

 the water. This method is now known to be fallacious, because 

 water cannot give out all its gas but by ebullition, and because the 



