440 
variety of elements sometimes found 
in water, and the extremely small 
quantities of them, are discouraging 
circumstances when the object of ana- 
lysis is to ascertain both the kind and 
quantity. of these foreign elements. 
They may both, however, be investi- 
gated without much labour, when pro- 
per means are used; and, perhaps, a 
little practice may render a person 
qualified to undertake the task, who 
is no great adept in chemical science 
in general. 
Most spring-water that is obtained 
by sinking some depth into the earth, 
contains lime held in solution by some 
one or more acids, particularly the 
carbonic and sulphuric acids. 
It is to these salts, the carbonate 
and sulphate of lime principally, that 
spring-water owes its quality of hard- 
ness, as it is called; a very singular 
and astonishing quality, when it is 
considered as produced by so ex- 
tremely small a portion of the earthy 
salt. The other earthy salts, or those 
of magnesia, barytes, ‘and alumine, 
produce the same effect nearly, but 
they are rarely met with, compared 
with those of lime. 
When any earthy salt is dissolved 
in pure distilled or rain water, it in- 
creases the specific gravity of the 
water; but, in the instance of spring- 
water in general, this test is rendered 
of little use, because the increase of 
spe. gra. is so small as almost to elude 
the nicest instrument that can be made. 
I have however an instrument, made 
by an artist in this town, which is no- 
thing more than the common glass 
hydrometer, but with an unusually 
fine small stem, that shows the supe- 
rior gravity of spring-water. It can- 
not, indeed, be brought in competition 
with other methods for ascertaining 
the relative hardness of spring-water, 
but it is a most useful instrument in 
other departments of chemical inves- 
tigation, particularly in determining 
minute portions of residual salt after 
precipitations.* It may well be con- 
ceived, that the sp. gravity cannot 
constitute a test of the hardness of 
* The scale of the hydrometer is one 
inch and a half long, and it is divided into 
25°, each degree corresponding nearly to 
*0004; the difference between distilled 
water and common spring-water is usually 
about 1° on the instrument; and that be- 
tween distilled or rain-water and the 
strongest lime-water is 4°. 
Proceedings of Public Societies, 
[June 7, 
water, when we find that one grain of 
earthy salt, dissolved in 2000 grains of 
pure water, converts itinto the hardest 
spring-water that is commonly 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 liquid, which con- 
tinues 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 
combined with the oil of the soap. It 
has a glutinous unpleasant feel when 
rubbed upon the hands, and soils glass 
and other vessels, so as to require hard 
pressure of a cloth to remove it. 
Though this test sufficiently distin- 
guishes hard water from soft or pure 
water, it is not equal to form an accu- 
rate comparison of the hardness 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 su- 
percarbonate of lime in solution; the 
addition of lime-water reduces the su- 
percarbonate to carbonate, which is 
insoluble, and falls down in the state 
of a white granular powder. When 
a spring contains nothing but super- 
carbonate of lime, which is the case 
with the water of an excellent pump 
in this neighbourhood, lime-water is 
the only test wanted to ascertain the 
proportion of salt init. Leta given 
portion of the spring-water be satu- 
rated by lime-water, adding it as long 
as milkiness ensues; the carbonate of 
lime is precipitated, and may be de- 
termined 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 dis- 
sélved 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 
combined with the carbonic acid. In 
this way I find the supercarbonate of 
lime, 
