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such change is produced if either the purulent matter, or solution of salts, be diluted; nor is it produced if the pus be previously coagulated by caloric: also the inspissated pus is coagulable by caloric as usual. No such inspissation is produced by these salts in mucous sputum, or in mucopurulent sputum, so that undoubtedly it is a criterion as discovered by Mr. Hunter in the case of muriate of ammonia, and with other neutral salts, as now manifested.

4. I endeavoured to find some easy tests for distinguish- and other tests, ing pus from mucus; but I did not succeed with the tanning principle; gallic acid; supersulphate of alumina; nitrate of silver, and other metallic salts; and as already said, varions acids. They all produced precipitation of these animal matters, but not with observable characteristic differences.

5. To observe the state in which the matter of pus is se- State in which creted, I procured the assistance of Mr. Maynard, the prepus is secreted sent house-surgeon of St, George's hospital, and Mr. George Ewbank, who had been on many occasions essentially 'serviceable in my inquiries. Square pieces of goldbeater's skin were applied to various sore legs after carefully removing the matter already secreted. In five or ten minutes the square pieces being removed, they were found wet with a limpid fluid. In this state they were inspected by the microscope, by which numerous globules were seen, In ten minutes farther the liquid was no longer limpid but opaque, like pus, in which the usual spherical particles were seen with the microscope as just mentioned.

Supposing objections might be offered on account of the -alteration of texture of the skin employed, square pieces of glass were also applied. The results were the same in both trials. The two gentlemen above named, as well as Dr. Richard Harrisou, and other pupils, who happened to be present, all concurred in the observation, that the limpid matter became opaque, and that while limpid it was, like pus, full of spherical particles,

(To be concluded in our next.)

V.

An Aecount of a New Gas, with a Reply to Mr. MURRAY'S last Observations on Oximuriatic Gas. By Mr. JOHN DAVY.

Mr Davy's theory op

posed by Mr.

Murray.

His experi

ments.

Objections,

Water present

SIR,

ABOUT

To MR. NICHOLSON.

BOUT six months since Mr. Murray undertook to oppose Mr. Davy's theory respecting oximuriatic gas, and to defend the old hypothesis, in which this substance is considered as a compound of oxigen and an unknown basis. called muriatic acid, and common muriatic acid gas as a compound of the same basis and water.

Independent of his general reasoning, the only arguments advanced by this gentleman in support of his opinions were derived from his own experiments, undertaken expressly for the purpose. His first attempt to discover oxigen in oximuriatic gas was by trying the action of this substance on carbonic oxide; and he concluded, that it did not exert any when the mixture of the two gasses, previously dried, was exposed to the influence of light. He then endeavoured to prove, that the addition of hidrogen to the mixture induced action, and the formation of carbonic acid gas. He also attempted to show that oximuriatic gas, if supplied in sufficient quantity, is capable of affording oxigen to sulphur in sulphuretted hidrogen, and of converting it into sulphureous or sulphuric acid.

To account for these supposed changes in consequence of the presence of hidrogen, he was obliged to imagine, in opposition to all experimental evidences, that the composition of muriatic acid gas is indefinite: that the unknown basis combines with different proportions of water, but always retains the appearance and the gaseous state of common muriatic acid gas, hitherto the only subject of experiment.

Having given this outline of Mr. Murray's mode of de fence of the old hypothesis, I shall briefly state the facts I ventured to oppose to it.

It was first shown, that muriatic acid gas, and the sulphuretted

ment.

phuretted liquor of Dr. Thomson, alone resulted from the in the experi action of dry oximuriatic gas on dry sulphuretted hidrogen ; and that the production of sulphuric acid in Mr. Murray's experiment was owing to his having admitted water.

My brother, Mr. Davy, next discovered the existence of New coma new gas made in the same way as the gas employed in pound. Mr. Murray's first experiments, in which he says he obtained carbonic acid, and possessed of the property of converting carbonic oxide into carbonic acid, it being a compound of oximuriatic gas and oxigen.

oxide.

Lastly, it appeared, that due allowance being made for Experiment to the difficulty of entirely excluding moisture, pure oximu- show that oximuriatic gas riatie gas is not capable of converting carbonic oxide into does not acicarbonic acid, when inflamed with a mixture of this gas and dify carbonic hidrogen. Thus, when 10 measures of carbonic oxide were subjected to the action of oximuriatic gas inflamed by an electric spark with hidrogen, only two measures disapappeared, 8 measures of carbonic oxide remaining unaltered. A result perfectly satisfactory, I conceived, considering the minute quantity of the gasses operated upon, not altogether amounting to half a cubic inch; and recollecting, that half a grain of water contains sufficient oxigen to convert about four cubic inches of carbonic oxide into carbonic acid.

nion.

Mr. Murray is of a different opinion. He considers, in Mr. Murray of bis last communication, the disappearance of two measures a contrary opí. of carbonic oxide, a demonstration, that oximuriatic gas is a compound of an unknown basis and oxigén. In the same paper, which is published in your Journal for June, he has given an account of the repetition of his experiment on the mixed gasses, employing pure oximuriatic gas; and he has arrived at the conclusion, "that the production of carbonic acid is established beyond the possibility of doubt."

I shall state the manner in which he conducted the experiment, and the evidences which satisfied him of the production of carbonic acid.

He exposed to light a mixture consisting of one volume His experi of carbonic oxide and of the same quantity of hidrogen ment in sup with twice that quantity of oximuriatic gas. After 36 hours port of it, he added ammoniacal gas to complete saturation, and, finding that most of the carbonic oxide had disappeared,

and

A new acid gas the cause

and that one of the ammoniacal salts formed had the property of effervescing with dilute nitric acid; he, without any additional proofs, drew the conclusion just mentioned, "that the production of carbonic acid in this experiment "was established beyond the possibility of doubt."

I have now to announce the existence of a new acid gas, of his mistake, which operated in Mr. Murray's experiment, without his knowledge of its presence, and was the cause of those phenomena, which he erroneously attributed to the formation of carbonic acid gas.

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Repeating this gentleman's experiment on the exposure of the mixture of the three gasses to light, and detecting, after the addition of ammonia, no traces of carbonic oxide; and perceiving, as he stated, an effervescence of the ammoniacal salt formed with nitric acid; I was induced to repeat also his experiment on the exposure of a mixture of carbonic oxide and oximuriatic gas to light without hidrogen. In this instance I obtained the same result, a total condensation by ammonia without the slightest remains of carbonic oxide.

So satisfactory were the details of Mr. Murray's experiment, the result of which was asserted to be, "that dry carbonic oxide gas and oximuriatic gas do not act on each other;" that at first I could hardly believe, but that water was somewhere concealed in the apparatus, and I gave myself much trouble to discover its source, but in vain.

The next step I took was to examine the gas, that resulted from the now evident action of oximuriatic gas on carbonic oxide. Mr. Brande was present at the time.

Finding that it did not fume when thrown into the atmosphere, that it had a most intolerable suffocating odour, that it was colourless, that it did not act on the mercury, and that water absorbed it very slowly, we immediately perceived, that it was a new and peculiar compound of carbonic oxide and oximuriatic gas, and this conclusion is fully confirmed by the investigation I have made of its properties.

1 shall now mention only the most striking circumstances respecting it. It is my intention to give a full account of the experiments I have made on it, in a paper which I shall soon do nyself the honour of offering to the Royal Society.

tion.

as an acid.

I have found, that it is produced in two or three minutes Its producwhen a mixture of equal volumes of carbonic oxide and oximuriatic gas is exposed in a tube over dry mercury to bright sunshine; and that the condensation, that takes place in their union, is exactly equal to one volume, so that this is the heaviest gas known excepting silicated fluoric acid gas. I have also ascertained, that it may be at any time formed without the direct rays of the sun-Light alone being necessary. Its acid character is well defined. Its characters It reddens litmus and combinés with ammonia; and its saturating power is so great, that it condenses four times its volume of this gas, forming a perfectly neutral salt, deliquescent, and of course very soluble in water; and its attraction for the dry volatile alkali is so strong, that it decomposes carbonate of ammonia, and is not expelled by The decomposition of this Decomposi acetic acid from this alkali. ammoniacal salt with effervescence by dilute nitric acid tion of its amdeceived Mr. Murray. Water in this instance is decomposed, its hidrogen is abstracted by the oximuriatic acid to form muriatic acid, and its oxigen by the carbonic oxide

moniacal salt.

to produce carbonic acid, which is disengaged. This will Other properappear evident, when it is known, that the new gas neither ties of it. inflames on the passage of the electric spark with either oxigen or hidrogen alone, but that it detonates violently with a mixture of oxigen and hidrogen in proper propor

tions, aud affords only muriatic and carbonic acid gas. The Action of meaction too of several metals and their oxides on this gas is tals on it. perfectly consistent with, indeed is quite demonstrative of its being a compound of equal volumes of carbonic oxide and oximuriatic gas, so condensed as to occupy half the of the mixture of the two. Thus tin, zinc, and anspace timony, respectively heated in it in small bent glass tubes over mercury rapidly decompose it. In each instance carbonic oxide, exactly equal to the volume of the gas decomposed, is liberated, and a compound of the metal employed and oximuriatic gas is produced, the same precisely as is formed by the combustion of the metal in oximuriatic gas. The decomposition too is just as readily effected by the oxides of zinc and antimony; with the first carbonic acid gas is obtained, and a compound of zinc and oximuriatic

gas;

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