Succinate of Soda and Succinate of Am monia are also tests for iron.
In applying these agents it is necessary not to use more than is sufficient for the purpose ; because an excess of them re dissolves the precipitate. The best mode of proceeding is, to heat the solution con taining iron, and to add gradually the so lution of succinate, until it ceases to pro duce any effect. A brownish precipitate is obtained, consisting of sucei nate of iron. This, when heated with a little wax, in a low red heat, gives an oxide of iron, con taining about seventy per cent. of the metal.
The succinates, however, precipitate alumine, provided there be no considera ble excess of acid in the aluminous salt. On magnesia they have no action, and hence they may be successfully employed in the separation of these two earths.
Phosphate of Soda.—An easy and valua ble method of precipitating magnesia has been suggested by Dr. Wollastan. it is founded on the property which fully neu tralized carbonate of ammonia possesses ; first to dissolve the carbonate of magnesia • formed, when it is added to the solution of magnesian salt. For this purpose a so lution of carbonate of ammonia, prepared with a portion of that salt which has been exposed, spread on a paper, for a few hours to the air, is to be added to the so lution of the magnesian salt sufficiently , concentrated ; or to a water suspected to contain magnesia, after being very much reduced by evaporation. No pre cipitate will appear, till a solution of phosphote of soda is added, when an abun dant one will fall down. Let this be dried in a temperature not exceeding 100° Fah renheit. One hundred grains of it will indicate nineteen of magnesia, or about sixty-four of muriate of magnesia.
Olitriate of Lims.—Muriate of lime is principally of use in discovering the pre sence of alkaline carbonates, which, though they very rarely occur, have sometimes been found in mineral waters. Of all the three alkaline carbonates, mu tilde of lime is a sufficient reagent; for those salts separate from it a carbonate of lime, soluble, with effervescence, in mit riati c acid.
With respect to the discrimination of the different alkalies, potash May be de-' tected by muriate of plating. Carbonate of ammonia may be discovered by its smell ; and by its precipitating a neutral: salt of alumine, while it has no action ap parently on magnesian salts.
To estimate the proportion of an alka line carbonate present in any water, satu rate its base with sulphuric acid, and note the weight of real acid which is required.
Now 100 grains of real sulphuric acid saturate 121.48 potash, and 78.32 soda.
Analysis of waters by evaporation.
The reader, who may wish for rules for the complete and accurate analysis of mineral waters, will find in almost every chemical . work a chapter allotted to this subject. He may consult Kirwan's "Essay on the Analysis of Mineral Waters," London, 1799.
Before evaporation, however, the ga seous products of the water must be col lected, which may be done by filling with , it a large glass bottle, or retort, capable of holdiug about fifty cubic inches, and furnished with a ground stopper and betit tube. The bottle is to be placed up to its neck in a kettle filled with brine, which must be kept boiling for an hour, or two, renewing, by fresh portions of hot water, what is lost by evaporation. The" disengaged gas is conveyed, by a bent tube, into a graduated jar, filled with, and inverted in, mercury, where its hulk is to be determined. On the first impression of, the heat, however, the water will be ex: panded, and portions will continue to es-i cape into the graduated jar, till the water has obtained its maximum of temperaturel This must be suffered to escape, and its quantity to be deducted from that of the water submitted to experiment.
In determining, with precision, the quantity of gas, it is necessary to attend to the state of the barometer and ' meter.
The gases most commonly found in mineral waters, are carbonic acid; sulpha. • reefed hydrogen ; nitrogen ; oxygen gas; and, in the neighbourhood of volcanoes only, sulphureons and gas.. • To determine the proportion of the gases, constituting any mixture obtained from a mineral water in the foregoing . mariner, the following experiments may he made. If the use of re-agents has not detected the presence of sulphuretted hydrogen, and there is reason to believe, froin the same evidence, that carbonic acid forms a part of the mixture, let a • graduated tube be nearly filled with it over quicksilver ; pass up a small portion of solution of potash, and agitate this in contact with the gas ; the amount of the diminution will show how much carbonic acid has been absorbed ; and, if the quan tity submitted to experiment was an ali quot part of the whole gas obtained, it is easy to infer the total quantity present in the water. The unabsorbable resi duum consists, most probably, of oxygen and azotic gases ; and the proportion of these two is best learned by the use of Or. Hope's eudiometer.