200 CATARACTS, AND INUNDATIONS. 



Such are the different considerations JM. Fourcroy has thought 

 necessary to exhibit, that the effects of re-agents on waters may be 

 better ascertained 5 but whatever may be the degree of precision 

 to Wtjich researches of this nature may be carried; however exten- 

 sive the knowledge we may have acquired concerning the degrees 

 of purity, and the different states of such substances as are com- 

 bined with mineral waters, for the purpose of discovering ti 

 principles, if it still remains a fact, that each of these re-a^nls is 

 capable of indicating two or three different substances dissolved in 

 these waters, the result of their action will always be subject to un- 

 certainty. Lime, for example, seizes the carbonic acid, and preci- 

 pitates salts with the base of alumine, and of magnesia, as will as 

 the metallic salts. Ammoniac produces the same effect. Fixed 

 alkalis, besides the above mentioned salts, precipitate those with 

 base of lime. The calcareous prussiat, the prussiat of potash, and 

 gallic alkohol, precipitate the sulphat and carbonat of iron. The 

 nitric solutions of silver and of mercury, decompose all the sulphu- 

 ric and muriatic salts, which may be various both in quantity and 

 in kind, in the same water, and are themselves decomposable by al- 

 kalis, chalk, and magnesia. Among this great number of compli- 

 cated effects, how shall we distinguish that which takes place in the 

 water under examination, or by what means shall we ascertain 

 whether it is simple or compounded I 



These questions, though very difficult, for the time when the ex- 

 pedients of cheuiistrj were little known, are nevertheless capable of 

 being discussed in the present state of our knowledge. It must first 

 be observed, that the nature of re-agents being much better known 

 at present than it was some years ago, and their reaction on the 

 principles of water better ascertained, it may, therefore, be strongly 

 presumed that their application may be much more advantageously 

 made than has hitherto been supposed ; nevertheless, among the 

 great number of excellent chemists who have attended to the ana. 

 lysis of waters, Messrs. Bauire, Bergman, and Gioanetti, are almost 

 the only persons who have been aware of this great advantage. We 

 have been long in the habit of examining mineral waters by re- 

 agents, in very small doses, and often in glasses ; the phenomena of 

 the precipitations observed have been noted down, and the experi- 

 ment carried no further. Baume advises, in his ehimistry, that a 

 considerable quantity of the mineral water under examination, 



