the JVater of Kilburn Wells. 119 
experiment, that the precipitate should be separated as soon as 
formed ; otherwise, if there be iron contained, that will also be 
precipitated together with calcareous earth). 
EXPERIMENT XU. 
On dropping muriated terra ponderosa into the fresh water, 
the earth is precipitated ; which also happens, but in a less 
degree, if the water has been boiled ; this proves it to contain 
vitriolated soda and magnesia, the other selenite. 
To ascertain the quantity of vitriolic acid contained in these 
salts, as much pure acetous acid was first added to one pound of 
the water, as was required to saturate the earth. Then a so- 
lution of terra ponderosa in nitrous acid was carefully dropped 
into the mixture, till no more precipitate was formed ; the 
thus regenerated spar was carefully collected, edulcorated, 
and dried, when it weighed 60 grains. Now, if 100 grains 
of ponderous spar contain 22 grains of vitriolic acid, it will 
follow, that one pound of the Kilburn water contains about 
13 grains of this acid. 
EXPERIMENT XIII. 
Vitriolated silver was dissolved, and added to the Kilburn 
water, previously impregnated with pure nitrous acid, to effect 
a solution of the earthy particles contained in it. The silver 
combined with the muriatic acid in the water, and formed a 
luna cornea : but I do not estimate the quantity of the acid in 
the water from this experiment, which is liable to deceive, as 
well as the preceding. This will appear on comparing the 
result with the real quantity of vitriolic acid, as given in the 
contents of the water, annexed to these experiments. 
