Spring and Mineral Waters. 59 
those metals. Onegrain of lead precipitated 
by sulphuretted: hydrogen, would be suftici- 
ent to give a great many gallons of water a 
dark brown tinge. When sulphuretted’ hy- 
drogen is found in mineral waters, as those of 
Harrogate, it may be known by the smell; 
but solutions of lead are much superior tests, 
giving a black or brown tinge to such waters 
immediately. 
8. Tincture of galls and prussiates of potash 
and lime tests. ‘These are proper for the de- 
tection of iron, the former giving a black 
precipitate and the latter a blue one; but a 
portion of the solution of oxymuriate of lime 
requires to be added previously to the water, 
if it contains the green oxide of iron in-solu- 
tion, in order to convert it to the red oxide. 
There are many other tests than those I 
have enumerated, but they are more than can 
usually be wanted in the analysis of ordinary 
springs. My objectis not to givea catalogue 
‘of tests; but to shew in what manner their 
application may be improved, and reduced to 
a system intelligible to moderate proficients. 
Fhe improvements F would propose in the 
use of tests are, that the exact quantities of 
the ingredients in each test should be previ- 
ously ascertained and marked on the Jabel of 
the bottle; this might easily be done in most 
