I must, however, mention here a singular fact. Having myself subjected caoutchouc to destructive distillation, I obtained none of Mr. Enderby's oil; but on adding sulphuric acid to the more volatile products, I got what I conceived to be impure eupion. My failure in procuring the new oil I ascribe to a difference in the temperature employed.

Professor Liebig is inclined to the opinion that the other substances described by Reichenbach are products of reaction, and not educts. But I venture to remind him that creosote, for example, may by detected in tar, by its smell and by its antiseptic virtue; that, according to Reichenbach, both eupion and paraffine may be sufficiently purified, by rectification alone, to exhibit their characteristic properties; and that paraffine may be extracted from the petroleum of Rangoon, in a state of absolute purity, without the employment of any more active solvent than sulphuric æther.

M. Hess, in a note read in the Imperial Academy of Sciences of St. Petersburg, on the 11th of March* 1836, mentions some circumstances which are highly interesting in reference to the present subject. After referring to the analogy of the oil of petroleum with the eupion of Reichenbach, (an analogy which I had demonstrated in a paper read to the Royal Society of Edinburgh in December 1834, and since. published in their Transactions,) he states that in, following Reichenbach's process for the preparation of eupion from oil. he obtained a liquid of sp. gr. 071, which by the action of potash he obtained at last so light as 0·648, and boiling from 68° Fahr. to 110° Fahr.

This liquid he found to have the composition of olefiant gas; it contained, he says, but very little eupion, which might be separated by sulphuric acid.

Now my experiments above described render it extremely probable that M. Hess's liquid is identical with that of Mr. Enderby; and that the oil separated from it by sulphuric acid is not eupion, but the second oil analysed by me.

As M. Hess had previously shown that the pure oil of petroleum had the same composition as olefiant gas, and was in its properties, as I had also proved, very analogous to eupion, he thinks it highly probable that the composition of eupion is

the same.

He then proceeds to divide the very numerous compounds, which agree in containing, like olefiant gas, about 85.7 per cent. of carbon, and 14.3 per cent. of hydrogen, into two series. The one, of which paraffine, eupion, and olefiant

* Annales de Chimic, vol. lxi. p. 331.

gas

are examples, he calls passive, because they do not act on sulphuric acid; the other, of which Faraday's quadro-carburetted hydrogen and the oil obtained by himself, as well as Mr. Enderby's oil (if the two latter be not identical), are specimens, he calls active, as they act strongly on the same acid. I have mentioned his views here, in order to direct attention to the striking fact, established by my experiments, that Mr. Enderby's oil, belonging to one of these classes, is, partially at least, converted by the action of sulphuric acid into a liquid belonging to the other series, and retaining the same composition.

Another circumstance well worthy of notice is the fact that several of the liquids in question yield uniform results as to composition, even when the portions analysed differ in density and volatility. This has been shown to occur likewise in the oils of turpentine and lemons, and seems to indicate the existence of an almost unlimited number of polymeric combinations of carbon and hydrogen.

When Mr. Enderby's liquid was first made known it was stated to be an excellent solvent for caoutchouc, which, from its great volatility, would have rendered it extremely valuable. But it is necessary to state, that I have not yet seen one specimen of it which, under any circumstances, in my hands, possessed this property. Two gentlemen informed me that they had succeeded in dissolving caoutchouc by means of it; but when asked to repeat the experiment with the same liquid they both failed. If therefore this liquid be a solvent for caoutchouc, it must be under conditions with which I am not acquainted.

LXIV. Experiments on Gaseous Interference. By WILLIAM CHARLES HENRY, M.D., F.R.S.*

THE singular power exerted by certain gases, of suspend

ing the action of finely divided platina on mixtures of oxygen and hydrogen, was first observed and announced by Dr. Turnert, shortly after Döbereiner's discovery. It was also about the same period noticed by Dr. Henry in the course of his researches on the application of platina to the analysis of complex gaseous mixtures. More recently Dr. Faraday has described similar interferences, affecting the • Read before the Chemical Section of the British Association at Bristol: and communicated by the Author.

+ Jameson's Journal, vol. xi. pp. 99 and 311.

Phil. Trans., 1824, p. 266.; [or Phil. Mag., First Series, vol. lxv. p. 272.-EDIT.] § Ibid., 1834, p. 71.

activity of prepared plates of the same metal. Various modes have been proposed of interpreting these phænomena. Dr. Turner (Chemistry, 5th edit., p. 647) observes, " One would be tempted to suppose that these gases act by soiling the metallic surface, though in some respects this explanation is not satisfactory." In the Essay by Dr. Henry already referred to (p. 282), it is suggested that this property " is most remarkable in those gases which possess the strongest attraction for oxygen, and it is probably to the degree of this attraction, rather than to any agency arising out of their relations to caloric, that we are to ascribe the various powers which the gases manifest in this respect." Finally, the latest writer on this subject, Dr. Faraday, concludes (par. 655.): "Whether the effect produced by such small quantities of certain gases depends upon any direct action which they may exert upon the particles of oxygen and hydrogen, by which the latter are rendered less inclined to combine, or whether it depends upon their modifying the action of the plate temporarily (for they produce no real change on it) by investing it through the agency of a stronger attraction than that of the hydrogen, or otherwise, remains to be decided by more extended experiments." It was in the hope of illustrating the nature of these interesting phænomena in gaseous chemistry that the following experiments were instituted.

The carbonic oxide and olefiant gases are stated by all the above-mentioned inquirers to possess, in the most remarkable degree, the property of interference. I have selected those gases as fitter subjects for experiment than others which manifest the same property, because, as Dr. Faraday testifies, they prevent combination, without at all injuring or affecting the power of the platina (644. and 6.), and hence exhibit the phænomenon in its simplest form. The platina which I employed was in the various conditions of (1.) plates prepared according to Dr. Faraday's method; (605.) (2.) sponge from calcination of the ammonia-muriate, either alone or moulded with China clay into small balls; and (3.) the black powder precipitated by the addition of alcohol to the solution of protochloride of platina in potassa, according to Liebig's process.

1. Carbonic Oxide.-To a mixture of oxygen and hydrogen, in the proportions required to constitute water, carbonic oxide was added, so as to form th,th, andth of the entire volume. The prepared plate when admitted caused no appreciable diminution, nor was any change observed during three or four hours in any of the three mixtures. The following morning evident but slight diminution was visible in all.

Since the gaseous products admit of exact analysis only over mercury, a fluid through which the plate cannot be passed without destroying the purity of surface essential to its activity, I was induced to employ balls of platina and China clay in the greater number of instances. Such balls, introduced over mercury into mixtures containing from th toth of carbonic oxide, produced no instantaneous action. But in the course of five minutes there was generally a visible diminution of volume, and in the space of two hours the action was complete. When the carbonic oxide formed a larger element of the mixture, as from th to 3rd, the action was still longer delayed. With one third there was scarcely any visible decrease of volume during the first hour; and even on the following day there remained much gaseous matter unconsumed. Thus the residue of a mixture of 35 cu. in. of carbonic oxide with 70 of hydrogen and oxygen in combining proportions (together 1.05), amounted after twentyfour hours' contact with the ball to ⚫82. The proportions were extensively varied between and th as limits; and between these it was observed, that combination to a greater or less amount was in all cases induced by a sufficient duration of contact. Carbonic oxide, it appears then, does not prevent but only retards gaseous union.

To ascertain the proportions in which the oxygen had been shared by the gases opposed to each other, the residue was washed with limewater or with caustic potassa. In all cases a notable diminution, due to the absorption of carbonic acid, was observed, and from the limewater carbonate of lime was precipitated. The quantity of carbonic acid so formed varied with the varying proportion which the carbonic oxide had borne to the hydrogen of the explosive mixture. When the hydrogen and carbonic oxide were present in equal volumes, and the oxygen was sufficient to saturate one of them only, I found that the carbonic oxide had appropriated to itself, in one experiment eight times, in another as much as ten times, the volume of oxygen that the hydrogen had taken. When the carbonic oxide was inferior in volume to the hydrogen, less oxygen was expended in the production of carbonic acid, but still considerably more in proportion than had combined with the hydrogen. It is then a general fact, that carbonic acid is generated in all cases in which carbonic oxide suspends the action of platina on mixtures of oxygen and hydrogen.

The next object of inquiry was to ascertain the action of platina in its various forms on mixtures of carbonic oxide with oxygen only. Dr. Faraday had noticed that at common temperatures a mixture of two volumes carbonic oxide and

one volume oxygen was unaffected by the prepared platina plate in several days." (574.) I found however that after four days' contact with the plate, an appreciable diminution had ensued. Thus 3 cu. in. of such a mixture were reduced to 2, indicating the formation of nearly cu. in. of carbonic acid. But the union of carbonic oxide with oxygen was much accelerated by causing the gases to stand in contact with the platina over a solution of caustic potassa, instead of distilled water, which had been used by Dr. Faraday. In such experiments there was a daily decrease of volume in the confined gases, till the fluid by ascending covered the greater part of the plate. Thus 34 cu. in. were reduced to 1 cu. in. in about seven days.

Platina in the form of sponge had been previously stated to cause the slow union of carbonic oxide and oxygen*. This action I found was also quickened by admitting potassa fusa with or without water above the confining surface of mercury. Thus 1.40 cu. in. of a mixture of carbonic oxide and oxygen in equivalent proportions became 1.25 in the first five minutes after introducing the platina sponge and potassa; in the next five minutes 1.15, and in half an hour much less than 1 cu. in. remained. In two hours less than half a cubic inch was left, and the potassa, by rising so as to moisten the sponge, terminated the experiment. Finally, the black powder of Liebig admitted into mixtures of carbonic oxide and oxygen became incandescent at the moment of contact, and continued to glow until all the carbonic oxide was converted into carbonic acid. Platina therefore, in all its forms, determines, at atmospheric temperatures, the union of carbonic oxide with oxygen. In the state of plate the change goes on with extreme slowness; in that of sponge, much more quickly; and in the most minutely divided condition of powder, with ignition and with great rapidity.

In this unequivocal action of platina upon mixtures of oxygen with carbonic oxide only, it appears to me, is to be found the interpretation of the property residing in the latter gas, of suspending the combining tendencies of hydrogen and oxygen in mixtures of the three gases. Possessing, as has been already shown, a stronger affinity for oxygen than is inherent in hydrogen, carbonic oxide seizes, when mingled with those two gases and exposed to the agency of platina, a much larger proportion of the oxygen than is due to its comparative volume. In such complex mixtures, just as in simple mixtures of carbonic oxide and oxygen, the slow formation of carbonic

* Phil. Trans., 1824, p. 267. [Phil. Mag., vol. lxv. p. 269.-EDIT.]