Imatges de pÓgina
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precipitate, which, when treated before the blow-pipe with a little soda, proved to contain lead; when treated with boracic acid, and a piece of iron wire, no indication of phosphoric acid was observed. Caustic soda, when boiled on the precipitate, took up some alumina. The concentrated solution of the earthy muriates produced no precipitate, when mixed with a saturated solution of sulphate of lime, thus proving the absence of barytes and strontia in the mineral water. Oxalate of ammonia indicated lime; and in the liquid, strained off from the

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mixture of sulphur produced by the decomposition of the sulphuretted hydrogen,) resembling very much, when a due proportion of iron was present, the precipitate formed by sulphuretted hydrogen in solution of the per-muriate of tin, for which, on a superficial examination, it may be mistaken; still more so, as the precipitate, its admixture of sulphur being soluble in hydro-sulphuret of ammonia, greatly disappears by the admixture of this re-agent. Muriatic, sulphuric, and nitric acid diminish the delicacy of the sulphuretted hydrogen as a test for lead. In a solution containing of its weight of the acetate of lead, the effect of the re-agent is still perceptible when the diameter of the fluid under exami nation amounts to about three inches of the acetate is still indi-. cated by the test, the diameter of the fluid being about one inch; and in a solution containing of the acetate of lead, the indication by the sulphuretted hydrogen is very distinct, when the diameter of the fluid is: but to of an inch. But if a solution of the concentration last mentioned contains about of its weight of muriatic acid, the change of colour, which the sulphuretted hydrogen produces, resembles that which would take place in a solution containing but of the salt of lead When the muriatic liquid is neutralized by carbonate of soda, the re-action appears with its full intensity. This is not quite the case when ammonia has been used for neutralization. Sulphuric and nitric acid act in a similar way; the former, however, even if present in a still smaller proportion. It is not the decomposition of the sulphuretted hydrogen which diminishes the efficacy of this test; (as one might suspect the muriatic acid to contain some chlorine, and both the other acids to contain some nitrous acid;) for the excess of the sulphuretted hydrogen present is proved, as well by the smell as by the copious precipitate, which an additional quantity of the salt of lead produces.

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The sulphuret of lead already formed cannot be re-dissolved by muriatic acid. Acetic acid does not diminish the effect of the test in any sensible degree; nor does chloride of sodium, even if the liquid contains of its weight. Muriate of ammonia, however, in a similar proportion, appears * not to hinder the full effect of the test in the first moments; but the re action produced becomes gradually less and less intense, although the fluid continues to contain an excess of sulphuretted hydrogen. When the solution of the lead is less concentrated, a smaller proportion of the acids, i was, of course, required to produce the same effect. The sulphuret of lead, precipitated from a solution containing an excess of the above acids, differs very much in its appearance from that where no acid is present; the former being of a denser aggregation, and a bluish black colour; the latter, blackish brown,


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oxalate of lime, phosphate of ammonia, together with pure ammonia, indicated the presence of magnesia.

The earthy carbonates, as well as the residue of the water*, gave no indication of manganese, when treated before the blowpipe, either with borax and nitre, or with soda.

Turmeric paper was not acted upon by the mineral water, even when concentrated by evaporation. Slightly reddened litmus paper turned blue, after some time, by the influence of the earthy carbonates. Tincture of galls proved, by want of re-action, that no iron was kept in solution.

A portion of the dry residue of the water was heated to redness. The ignited mass was dissolved in boiling water; and from the filtered solution, the sulphuric acid and the magnesia (of which a small quantity was found to be dissolved) were precipitated with muriate and hydrate of barytes. The boiling liquid, strained off from the precipitate, was evaporated to dryness, and the dry residue dissolved in a weak solution of carbonate of ammonia. The ammoniacal solution, after separating the last traces of lime by oxalate of ammonia, left, after evaporation and ignition, alkaline chlorides, one portion of which was dissolved in water, together with an adequate quantity of phosphate and carbonate of soda, and evaporated to dryness. The saline residue, by its perfect solubility in water, proved the absence of lithia in the mineral water. Another portion was dissolved in water, together with three times of its weight of per-chloride of platinum, and evaporated to dryness. The residue, when dissolved in spirit of wine, left some potassio-chloride of platinum. Thus the presence of potash and soda in the mineral water was evinced.

The constituents of the Bath water, according to the fore

The residue, when heated before the blowpipe, with an addition of carbonate of soda, does not cover the charcoal with a sublimate of oxide of lead, on account of the traces of this metal being defended from volatilization by the large quantity of the foreign substances inclosing them. The fused mass, however, left in the mortar, after a careful elutriation, some particles of metallic lead, even though but one or two grains had been employed for the experiment. The presence of lead in the residue may easily be ascertained also, by digesting on it from fifteen to twenty times of its weight, of a solution of acetate of ammonia, with some additional acetic acid. The fluid filtered off from the earthy residue is precipitated by sulphuretted hydrogen.

JAN.-MARCH, 1829.


going experiments, are therefore-chlorine, sulphuric acid, carbonic acid, potassa, soda, lime, magnesia, oxide of iron, alumina, and silica. Besides these, the mineral water contains some extractive matter; its residue, when evaporated, being coloured, and containing an admixture of carbon, after ignition. The relative proportions of these ingredients were ascertained in the following manner:—

.I.-14.47 cub. inch. of the mineral water were boiled in a suitable apparatus*, till the whole quantity of its gaseous contents *Having frequently occasion to determine the gaseous contents of mineral waters, the following little apparatus has proved to me, by frequent experience, to be a very useful one for that purpose.





A is a narrow cylindrical vial, containing from 2 to 3 cubic inches. Into its aperture a cork is thrust, and fastened down by a wire. (The lower surface of cork is well imbibed with a solution of mastic and turpentine in spirit of wine, in order to prevent its swelling, and consequently changing the bulk of the interior of the bottle.) C is a glass tube, of to inch bore, to be connected to the glass ball D, the neck of which is cylindrical, (if it widens towards its mouth, the cork is easily forced out when the water boils,) and its flat ground aperture of such wideness as to be easily closed by the finger. B, the tube for carrying off the gas, is of no more than about inch bore. When the apparatus is to be used, the bend bb of the tube B is first filled with mercury, by dipping it into that metal; then the cork E is thrust into the neck of the glass ball, entirely filled with the mineral water, by which process part of the water is forced into the tube C, and the air in the vessel A compressed in some degree. By holding the whole contrivance dexterously, with the bend of the tube B upwards, the column of mercury is sufficient to

was expelled. The gas collected over mercury was partly absorbed by a solution of caustic soda, and was found to consist, in one experiment, of 0.41 cub. inch. carbonic acid gas, and 0.29 cub. inch. residue (not absorbable by the alkali) in a dry state, (deduction being made for the elasticity of the aqueous vapour,) at 60° therm. and 30" bar. In another experiment, 0.38 cub. inch. carbonic acid gas, and 0.28 cub. inch. residue, were obtained, the mean of which gives, for one pint of the mineral water, (34.659 cub. inch., or 8767.7 grains,) 0.95 cub. inch. carbonic acid gas.

Twelve cub. inch of the mineral water, mixed with a sufficient quantity of diluted sulphuric acid, gave, when boiled till all disengagement of gas had ceased, 0.89 cub. inch. carbonic acid gas; which quantity gives, for one pint, 2.57 cub. inch. Thus one pint of the mineral water was found to contain 0.95 cub. inch. dry carbonic acid gas, at 60° therm. and 30" bar., in a free state, and (2.57 – 0.95) 1.62 cub. inch. = 0.75787 grains carbonic acid gas, united to the bases: making, for 1000 grains of the mineral water, 0.08609 grains carbonic acid.

prevent any gas from escaping. By the first effect of heat applied to the ball, part of the mineral water, which is afterwards boiled by the steam passing through it, is carried over into the vessel A. Boiling is to be continued till the increase of gas in the measuring tube has perfectly ceased. The advantages which this contrivance offers are-1. That the whole quantity of the mineral water under examination is submitted to continued ebullition, (no part of it being carried over into the measuring tube.) 2. That the quantity of water condensed in the measuring tube is, proportionately, very small. The air of the vessel A is so perfectly expelled, that the apparatus fills almost perfectly, (leaving, perhaps, an airbubble, of the size of a large pin's head,) when the apparatus is allowed to cool, with its tube B plunged into hot water. The cubical contents of the bottle A, with its pipes, are to be deducted from the volume of the gas obtained, and correction to be made, when the air in the bottle was of another temperature or density. In order to empty the little apparatus, when the experiment has been finished, it is best to connect it, when still hot, with its top downwards, to a common pair of bellows, and to drive the water out by a current of air. The air of the lungs is, of course, not proper for that purpose. Besides the little effect which it would have in drying the bottle, it would leave it partly filled with carbonic acid gas. The balls which I make use of, contain from about 7 to 12 cub. inch.; and I obtain from the smaller quantity, when the mineral waters are rich of gas, results which correspond as closely as can be expected, when the experiment is repeated. If the gas, not absorbable by the caustic alkali, is the object of research, I used to fill the little apparatus with pure carbonic acid gas, and collect the gas in the eudiometer itself, into which a solution of caustic potash has been injected before.

The residue, not absorbed by the caustic soda, gave, by détonation over mercury, 18.2 per cent. oxygen in one expe riment in another, 18.6 per cent.; and may be considered as atmospheric air, originally dissolved by the water, and partly decomposed by its protoxide of iron.

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II. 56000 grains of the mineral water were mixed with an excess of carbonate of soda, and evaporated to dryness. The residue was perfectly lixiviated with water, till all reaction on the test paper had ceased; and the saline solution was again evaporated, and kept in fusion over a spirit-lamp for some time, in order to decompose the soda-carbonate of magnesia which might have been formed. The fused mass, when dixiviated with boiling water, left some earthy carbonates, which were added to those obtained by the first lixiviation.

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H -JIV o III. One-third of the solution obtained in II, when supersaturated with muriatic acid, and precipitated with muriate of barytes, gave 76.394 gr. of sulphate of barytes; making, for 1000 grains of the mineral water, 2.48539 gr., equal to 0.85471 gr. of sulphuric acid*.

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IV. Another third of the solution, supersaturated with nitric acid, and precipitated with nitrate of silver, gave 20.442 gr. of chloride of silver; making, for 1000 gr. of the water, 1.09511 gr., equal to 0.27017 gr. of chlorine.

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The remaining third, being neutralised with muriatic acid, was evaporated to dryness, and re-dissolved in water, in order to try if any silica had been dissolved by the carbonate of soda; which was, however, not the case.

V. The earthy carbonates obtained in II. weighed, after ignition, 57.757 grains; 56.8 gr. of which, dissolved in *The equivalent numbers are computed according to Berzelius's latest experiments and computations. Vide his Annual Report to the Academy of Sciences of Stockholm for 1827.

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Wherever the nature of the precipitate allowed it, the filter was burnt, and the weight of its ashes deducted from the weight of the ignited precipitate. "When the precipitate was to undergo a further examination, as much as conveniently could be done was taken from the bytmaque ferit

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