of Spring and Mineral Waters. 293 
sp. gravity cannot constitute a test of the hardness of water, when 
we find that one grain of earthy salt, dissolved in 2000 grains of 
pure water, converts it into the hardest spring water that is com- 
monly found. 
We shall now proceed to notice some of the most useful tests 
in the analysis of waters. 
1. Soap Test.—When a piece of soap is agitated in distilled 
or pure rain water, a part of it is dissolved, producing a milky li- 
quid, which continues for many days unaltered. But when soap 
is agitated with hard spring water, the milkiness produced almost 
instantly degenerates into a curdy substance, which rises to the 
surface, and leaves the liquid below nearly transparent. This 
curdy substance is understood to be the earth of the salt com- 
bined with the oil of the soap. It has a glutinous, unpleasant 
feel when rubbed upon the hands, and soils glass and other ves- 
sels so as to require hard pressure of a cloth to remove it. Though 
this test sufficiently distinguishes hard water from soft or pure 
water, it is not equal to form an accurate comparison of the hard- 
ness of two kinds of water. 
2. Lime-water Test.—Most spring water, fresh from the well, 
will exhibit milkiness by lime-water; this is usually occasioned 
by the water holding supercarbonate of lime in solution; the ad- 
dition of lime-water reduces the supercarbonate to carbonate, 
which is insoluble, and falls down in the state of a white granular 
powder. When a spring contains nothing but superearbonate of 
lime, which is the case with the water of an excellent pump in 
this neighbourhood, lime-water is the only test waited to ascer- 
tain the proportion of salt init. Let a given portion of the spring 
water be saturated by lime-water, adding it as long as milkiness 
ensues ; the carbonate of lime is precipitated, and may be deter- 
mined by the usual means. I find it, however, rather preferable 
to add a small excess of lime-water to secure the precipitation of 
the whole acid: when the salt has subsided, the clear liquid may 
be poured off, and tested by an acid, and the salt may be dissolved 
by test muriatic or nitric acids. Thus the whole quantity of lime 
will be found; from which, deducting that added in lime-water, 
there will remain the lime in the spring water originally com- 
bined with the carbonic acid. In this way | find the SuPer cats 
bonate of lime, in five ounces of the water ‘above mentioned, 
consist of 48 lime, 
*77 carb. acid, 
1°25 
being about one grain of salt in 2000 of water. This kind of 
water is hard, and curdles soap 5 but it is much softened by boil- 
ing, and deposits the incrustation so often found in kettles, &e. 
If 
