180 An Analysis of two Mineral 
in a great measure, the action of the ordinary re- 
agents. When the water is boiled in contact with 
some of the metals, it becomes turbid; and the me- 
tal is partly oxydated, and partly dissolved. ‘The 
iron, which has been used in the construction of the 
baths, is almost destroyed: the tin, which lined a 
vessel used as a warm bath for children, has suffer- 
ed in like manner. _ If the water be only boiled and 
poured into a wine glass with a bright key in it, the 
liquor becomes turbid before it is cold. Copper 
seems to resist its action better; but this is only in 
a low temperature: for, if the water be boiled in a 
copper vessel, similar effects are produced ; a preci- 
pitate is formed and some copper is dissolved in the 
water. 1. This is readily proved by putting a 
bright piece of iron into the liquor, which, in a few 
hours, acquires a coppery coating.* Lead also I 
have found to be acted upon. 
I examined, with some minuteness, the precipi- 
tates formed by iron and by copper. 2. The first 
is of a yellow colour; and, though it is not mag- 
netic, it may be made so by the flame ofa blow- 
* This remark evinces the strong necessity of a chemi- 
cal examination of all the substances used as medicines. It 
is very common to warm the water with a view of quick- 
ening its laxative power. It is evident with what caution 
vessels, in which copper is an ingredient, should be used 
for this. purpose; or, rather, with what care they should be 
utterly avoided. . 
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