t 34 1 



VI. METALLIC SUBSTANCES 



a. Iron is a common ingredient in mineral 

 waters, whence they are called chalybeate. The 

 general method of drftinguiming this metal, is 

 by an infufion or powder of galls, Which turns 

 water containing iron of a purple or black co- 

 lour, deeper in proportion to the quantity of 

 Iron prefent. 



But the mod accurate method, is by means of 

 the Pruffian alkali (V) fully faturated with the 

 inflammable matter of dried blood. This al- 

 kali mixed with a chalybeate water turns the 

 latter immediately blue, and depofits the iron in 

 a powder of the fame color. 



b. Copper in water is precipitated in a red 

 powder by the fame alkali. 



c. Zinc is precipitated in a white powder by 

 the Pruffian alkali. Although this alkali preci- 

 pitates all the metallic fubftances from acids, fo 

 that they may be diftinguilhed from one another, 

 it does not any of the earths. 



d. Arsenic has been fufpected in fome mineral 

 fprings, but I am acquainted with no proof of 

 it. However, it may poilibly happen that water 

 running through arfenical veins, may carry off a 

 quantity of arfenic. To difcover this, the water 



{x) The Pruffian alkali is made of equal quantities of dried 

 ox-blood, and fixed alkali. Thefe are to be burnt together 

 jn a crucible, and the afhes difiblved in a fufficient quantity 

 ©f water, when we enter on our experiments. 



lliould 



