202 SPRINGS, RIVERS, CANALS, LAKES, 



other pounds, of the same mineral water, a drachm or two of ammo- 

 niac perfectly caustic, or causes ammoniacal gas, disengaged by 

 heat from the alkali, to pass into the water. When the water is 

 saturated, it is it ft at rest in a close vessel for twenty four hours; 

 if a precipitate be afforded, it can only consist of ferruginous or 

 magnesian, or aluminous sails, whose nature is examined by the 

 different methods mentioned in the foregoing paragraph. But the 

 action of ammoniacal gas being more fallacious than that of lime 

 water, which produces the same decompositions, it must be ob- 

 served that ; his last should only be used as an assistant means, which 

 does not afford results equally accurate with those produced by the 

 former re-;iger,t. 



When salts with base of aluminous earth, or magnesia, have been 

 discovered b> lime water, or by ammoniacal gas, the cau?>tic fixed 

 alkalis may be used, to distinguish those with base of lime, sudi as 

 sulphat iind muriat of lime. For this purpose Fourcroy precipitates 

 some pounds of the water, which is examined b) either of these 

 liquid alkalis, till it no longer produces any ttirbidness. As this 

 alkali decomposes salts with a base of aluminous earth, as well as 

 those composed of lime; if the precipitate resembles in its form, 

 colour, and quantity, that which lime water has afforded, it may 

 be presumed that the water does not contain calcareous salt, and 

 the chemical examinations of the precipitate usually confirms this 

 si* puion: but if the mixture is much more turbid than that made 

 with lime water; it' the deposition be much heavier, more abundant, 

 and move readily afforded, the lime is mixed with magnesia or 

 alunmie. This is ascertained by treating the precipitate after the 

 different method* before explained. It may easily be concluded, 

 that iron precipitated by re-agents, at the same time as the saline* 

 terrestrial substances, is easily known by its colour and its taste; 

 and that the small quantity of this metal separated iu these pro- 

 ces*es, is not sufficient to eff ct the results. 



It were useless to explain at large the effects of sulphuric acid, 

 nitrous acid, gall-nuts, or of the calcarrou* and alkaline prussiats, 

 employed as re-agents on mineral waters. The general account of 

 these effects which has already been jveii may Curtice; it need 

 therefore only be noticed, that wiien they are mixed in large doses 

 with these wateis, and the preripitates collected, the nature and 

 quantity of their principles may be more accurately ascertained, a$ 



