Mineral Waters. 273 



is precipitated white by the Prussian alkali ; but 

 as the precipitate from many other metals is of 

 the same colour, we must have recourse to eva- 

 poration to dryness, and then examine the resi- 

 duum. If it is zinc, it will convert a small plate 

 of copper into brass. If arsenic is supposed to 

 be contained in mineral waters, we must evapo- 

 rate them to dryness, and judge by the smell 

 when the residuum is made red-hot, or by trying 

 if it tinges copper white. 



It has here been endeavoured to give some ge- 

 neral notions respecting the action of re-agents in 

 the analysis of mineral waters. But it must be re- 

 membered that these analyses are not to be at- 

 tempted but by a master of the science and of the 

 art ; so numerous and delicate are the minutiae 

 which must be taken into consideration, and so 

 nice are the various manipulations which are 

 demanded. 



