760

Appendix.

d.

may be separated by dissolving the potash in diluted muriatic acid, and filtering thesolution. 100 grains of sulphate of potash indicate 42 - 72 cubic inches of ssl-phureous acid gas, which being subtracted from the bulk of the gas absorbed by thepotash, leaves the bulk of the carbonic acid gas.

. Oxygen gas, after the above gases are separated, may be examined by means ofthe solution of sulphate of iron saturated with nitrous gas. * A small graduatedtube filled with the air to be examined is to be plunged inta this solution, and movedbackwards and forwards for a lew minutes. The whole of the oxygen is rapidlyabsorbed, and by marking the greatest absorption, its bulk in a given quantity ofthe air is ascertained.e. Azotic or nitrogen gas is discovered by not being at all affected by endiometricafprocesses.3. Alkalies, andALKALiNE.EAnTHy, and metallic cabonatf.s. Alkalies, even in mi-nute quantities, are discovered in water by reudering infusion of turmeric or paper stainedwith it brown. * When the change is permanent, the fixed alkalies may be supposedto be present; when fugacious, the alkali is ammonia. An infusion of Brazil-woodis rendered blue by the alkalies ; but this also is the case with the alkaline and earthycarbonates?, and the addition of sulphuric acid produces effervescence. Tincture ofnutgalls discovers iron j the colour is violet if alkaline carbonates or earthy salts bealso present; dark purple indicates other alkaline salts ; purplish red, sulphuratedhydrogen gas ; and whitish and then black, sulphate of lime. Boiling the water pre-cipitates the earthy and metallic carbonates.

The following substances of this class set down in the first column are incompatible,or cannot exist in mineral waters, with the salts placed in the opposite column.

{Fixed alkaline sulphates.«'7t.' fSulphate or magnesia.i of iron.

Alkaline carbonates

.Earthy carbonates

(Ni

Muriate of baryfes.of lime,of magnesia.

itrate of lime.

f Su Iphate of iron.

it

Carbonate of magnesia

' Muriate of barytes.C Sulphate of lime.1 Alum.(^Muriate of lime.

a. Alkalies and their carbonates are ascertained to be present in mineral waters by^the tests already mentioned ; and by the water, after being boiled, throwing down aprecipitate on the addition of muriate of magnesia. The volatile nature of ammo-nia easily distinguishes it if present, which is very seldom; and the best test fordetermining whether the fixed alkali be potash or soda is muriate of platina ] , whichforms an immediate precipitate with potash or any salt containing it, but is not atall affected by soda* The quantity of an alkali is determined by saturating it withsulphuric acid, and noting the quantity of real acid 4 necessary ; setting down, forevery 100 grains of real a( id used, 121-48 of potash, or 7 8*32 of soda; and the lossof weight produced by the effervescence on drepping in the acid, being added to theabove, shows the quantity of an alkaline carbonate.

b. Earthy carbonates. If the water contains sulphureted hydrogen gas, this mustbe separated by exposing the water for a considerable time to the air, before thequantities of the earihy carbonates can be estimated. After thus exposing it, boilthe water for fifteen minutes, filter it when cold; and treat what remains on the.filter with muriatic acid, which will dissolve the carbonates of lime, of magnesia,and of iron. The residuum, which may contain carbonate of alumina, and per-haps sulphate of lime, is to be dried in a red heat, and its weight noted ; and thenboiled in a solution of carbonate of soda. The soda is next to be saturated with

1 Dr. Henry.

2 This test is sufficiently delicate to detect soda when it amounts to j^th partonly of the water.

3 Sulphate of lime likewise produces the same effect.

* For a rule to determine the quantity of real acid in a diluted acid, see introduction.