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absolutely necessary a rudder should be hung before they can be repaired, which, with good smiths, on board a ship, would require several days.

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Figure 4th represents the rudder composed of the materials I propose; by which will be seen the difference in bulk of the composition cap and the spare lower cap as represented in fig. 1. It will also be seen, that the alteration I propose strengthens the rudder below, as the space required for its working round the end of the cap in fig. 1. is much larger than in fig. 4.; it also hangs closer to the stern post below.

It is not only king's ships that should be supplied with the means of putting together as effective a temporary rudder as possible, but also Indiamen, and all merchant-ships going long voyages; and having such, I have no doubt two good carpenters in a merchant-ship, would put one together in twenty-four hours. Plymouth, 14th Feb. 1829.

Analysis of the Mineral Water of Bath.

[Communicated by Mr. A. Walcker.]

SINCE the latest experiments which the springs of this celebrated watering-place have been submitted to by Dr. Scudamore, our attention has been directed, by the masterly analysis of the Carlsbad and some other Bohemian springs by Berzelius, to look out, in the analysis of mineral waters, for several ingredients which were previously not supposed to exist in them. From this consideration, I was induced to subject the Bath water to a new analysis; and, although I wished to spare the reader the perusal of its dull details, yet I think it necessary to state briefly the processes which I have followed, in order to enable him to judge what reliance may be placed in their

correctness.

I am indebted for the supply of the mineral water to Mr. R. F. George, M. C. S. of Bath, who was kind enough to have it bottled, with due precautions, under his own inspection, from the pump in the pump-room.

The mineral water, when I received it, was very slightly turbid; the suspended precipitate appeared to consist chiefly of silica, an excess of muriatic acid and application of heat

having but very little effect in restoring its transparency. The specific gravity of the water at 60° F. was found to be 1.00202. In the filtered mineral water, nitrate of silver indicated the presence of chlorine.

When evaporated to of its original weight, and strained off from the precipitate formed, solution of starch and nitrous acid gave no indication of iodine; nor was bromine to be detected by the addition of chlorine; nor nitric acid by boiling it with a gold leaf, and a due quantity of sulphuric acid.

The residue of the water (the carbonates of which had been converted into acetates, in order to prevent the fluosilic acid, if present, from being carried off too rapidly along with the carbonic acid gas) gave no indication of fluoric or fluo-silicic acid, when treated with sulphuric acid in a platinum vessel, covered with a wet watch-glass.

Ebullition proved the presence of carbonic acid in the mineral water, by the precipitation of carbonate of lime.

Muriate of barytes indicated sulphuric acid.

A portion of the mineral water, to which an excess of carbonate of soda was added, was evaporated to dryness, and the residue dissolved in water. A part of this solution was supersaturated with nitric acid, and precipitated with an excess of nitrate of silver. The liquid, separated from the chloride of silver, gave no indication of phosphoric acid, by being duly neutralized with ammonia; nor could any indication of phosphoric acid be obtained, when the solution was precipitated with muriate of barytes, and the fluid strained off from the sulphate of barytes was mixed, after ebullition, with an excess of ammonia. The earthy carbonates obtained in this experiment left silica, when dissolved in muriatic acid. The muriatic solution indicated iron, by the addition of ferro-prussiate of potash. Sulphuretted hydrogen produced in the acid solution a slight precipitate of sulphuret of lead.* Ammonia produced a

* In a solution which contains at the same time oxide of lead and peroxide of iron, sulphuretted hydrogen does not produce a precipitate of lead, till the peroxide of iron present is reduced to the state of protoxide; and sulphuret of lead, already formed, can be re-dissolved by the addition of a solution of per-chloride of iron. The sulphuret of lead, whenever it is precipitated from a solution which contained at the same time a peroxide salt of iron, appears of a lighter colour, (from the ad

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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 a 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 3 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: 6 of the acetate is still indicated 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. butto 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.reaction 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. 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 $1.3 latter, blackish brown. ཨཐཱ་མི * an giong việc

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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.

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A portion of the dry residue of the water was heated to redThe 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.

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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.

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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

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