' 7 ; 
WATERS, MINERAL. 
1 . If a watpr, which is precpitated by ox- 
alic acid, become milky on adding a wa- 
tery solution of carbonic acid, or by blow’- 
ing air through it from the lungs, by means 
of a quill or glass tube, we may infer that 
lime (or barytes which has never yet been 
found pure in waters) is present in an un- 
combiiicd state, 
2. If the oxalic acid occasion a precipi- 
tate before, but not after boiling, the lime 
is dissolved by an excess of carbonic acid. 
3. If after boiling, by a fixed acid. A 
considerable, excess of any of the mineral 
acids, however, prevents the oxalic acid from 
occasioning a precipitate, even though lime 
be present j because some acids decompose 
the oxalic, and others, dissolving the oxa- 
late of lime, prevent it from appearing. 
(Vide Kirwan on Waters, page 88). 
The oxalate of ammonia, or of potash, are 
not liable to the above objection, and are 
preferable, as re-agents to the uncombined 
acid. Yet even these oxalates tail to detect 
lime when supersaturated with muriatic or 
nitric acids ; and, if such an exbess be pre- 
sent, it must be saturated, before adding 
the test, with ammonia. A precipitate will 
then be produced. 
Tlie quantity of lime, contained in the 
precipitate, may be known, by first igniting 
it with access of air, which converts the 
oxalate into a carbonate ; and by expelling 
from this last the carbonic acid, by a strong 
hejt, in a covered crucible. According to 
Dr. Marcet, 117 grains of sidphate of lime 
give 100 of oxalate of lime, dried at 160° 
Fahrenheit. 
Fluate of ammonia is also a most delicate 
test of time. 
Barytic IFater.—l. Barytic water is a 
very effectual test for detecting the pre- 
sence of carbonic acid, with which it forms 
a precipitate, which is soluble with effer- 
vescence in dilute nitric, or better in mu- 
riatic acid. 
2. Barytic water is also a most sensible 
test of sulphuric acid and its combinations, 
which it indicates by a precipitate not so- 
luble in muriatic acid. 
Metals.— Of the metals, silver, bismuth, 
and mercury, are tests of the presence of 
'hydro-sulphurets, and of sulphuretted hy- 
drogen gas. If a little quicksilver be put 
into a bottle, containing water impregnated 
with either of these substances, its surface 
soon acquires a black film, and, on shaking 
the bottle, a blackish powder separates 
from it. Silver leaf and bismuth are speed- 
ily tarnished by the same cause. 
Sulphate, Nitrate, and Acetate of SiU 
fpr. — These solutions are all, in some mea- 
sure, applicable to the same purpose. 
Tliey are peculiarly adapted to the disco- 
very of muriatic acid and of muriates, with 
which they form a white precipitate. A 
precipitation, however, may arise from other 
causes, which it may be proper to state. 
The solutions of silver in acids are precipi- 
tated by carbonated alkalies and earths. 
The agency of the alkalies and earths may 
be prevented, by previously saturating them 
with a few drops of the same acid in which 
the silver is dissolved. The nitrate and ace- 
tate of silver are decomposed by the sul- 
phuric and sulphureous acids ; but this may 
be prevented by adding, previously, a few 
drops of nitrate or acetate of barytes,' and, 
after allowing the precipitate to subside, 
the clear liquor may be decanted, and the 
solution of silver added. Should a preci- 
pitate now take place, the presence of mu- 
riatic acid, or some of its combinations, 
may be suspected. To obviate uncertain- 
ty, whether a precipitate be owing to sul- 
phuric or muriatic acid, a solution of sul- 
phate of sijver may be employed, which, 
when no uncombined alkali, or earth, is pre- 
sent, is affected only by the latter acid. 
The solutions of silver are also precipi- 
tated by sulphuretted hydrogen, and by 
hydro-sulphurets; but the precipitate is 
then reddish, or brown, or black ; or it 
may be at first white, and afterwards be- 
come speedily brown or black. It is solu- 
ble, in great part, in dilute nitrous acid, 
which is not the case if occasioned by mu- 
riatic or sulphuric acid. 
The solutions of silver are precipitated 
by extractive matter ; but in this case also 
the precipitate has a dark colour, and is so- 
luble in nitrous acid. 
Acetate of Lead . — Acetate of lead is a test 
of sulphuretted hydrogen and of hydro-snl- 
phurets of alkalies, which occasion a black 
precipitate ; and if a paper, on which cha- 
racters are traced with a solution of acetate 
of lead, be held over a portion of water 
containing sulphuretted hydrogen gas, they 
are soon rendered visible, especially when 
the water is a little warmed. 
Muriate, Nitrate, and Acetate of Barytes. 
These solutions are all most delicate tests 
of sulphuric acid and of its combinations, 
with which they give a white precipitate, 
insoluble in dihite muriatic acid. They are 
decomposed, however, by carbonated alka- 
lies ; but the precipitates, occasioned by 
carbonates, is soluble in dilute muriatic or 
