THE

LONDON AND EDINBURGH

PHILOSOPHICAL MAGAZINE

AND

JOURNAL OF SCIENCE.

[THIRD SERIES.]

NOVEMBER 1836.

LXIII. On a volatile Liquid procured from Caoutchouc by destructive Distillation: with Remarks on some other empyreumatic Substances. By WILLIAM GREGORY, M.D., F.R.S.E., Lecturer on Chemistry.*

SOME years ago a patent was taken out by Mr. Enderby,

of London, for the production of a volatile inflammable liquid by the distillation of caoutchouc. This liquid possesses very remarkable properties. As prepared by Mr. Enderby, it is colourless, very fluid, has no taste, but a peculiar æthereal smell. Its specific gravity is very low, being = 0·680, and it boils at a temperature below 100° Fahrenheit. As no examination of this remarkable substance has yet been published, I venture to offer the results of some experiments which I have made on it at intervals during the last two years.

As Mr. Enderby purifies his oil by rectification alone, my first object was to push that process as far as possible, so as to get rid of the less volatile matters which might be present, By successive rectifications, carried on without ebullition at about 80° to 90° Fahr., I at last obtained a liquid having the specific gravity of 0.666 at 60° Fahr., approaching very nearly to that of the eupion of Dr. Reichenbach, obtained by the distillation of oil, viz. 0.655. The new liquid, however, is not eupion, for it boils at about 90° Fahr., and is instantly

• Communicated by the Author.

Third Series. Vol. 9. No. 55. Nov. 1836.

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decomposed by oil of vitriol; while eupion boils at 110° Fahr., and resists the action of that acid.

The boiling-point of the new oil is not constant. That of sp. gr. 0670 begins to boil at 95° Fahr., but the temperature soon rises, and towards the end of the distillation reaches 170° Fahr. Consequently, we cannot consider it as an unmixed compound.

Having taken some of this liquid with me to Giessen last year, I submitted it to analysis under the eye of Professor Liebig. Although I did not expect any very satisfactory result from the analysis of a substance confessedly not free from mixture, I was rather surprised to obtain results indicating a composition, in 100 parts, identical with that of olefiant gas.

I next proceeded to examine the action of sulphuric acid on the new liquid. When the acid is added to it in large quantity, part of the oil is decomposed instantaneously, while the rest is dissipated by the heat evolved, leaving a black semifluid mass. But if the acid be added gradually to the oil at the bottom of a long tube, which is closed by the thumb and cooled down after each addition, a colourless liquid is obtained, swimming on the surface of the black mass above mentioned. When the addition of new acid causes no further development of heat, the liquid may be decanted, washed with solution of potash, and rectified over chloride of calcium.

This liquid has properties very distinct from those of the oil which has yielded it. It has acquired an aromatic smell, resembling that of turpentine, and it now boils at about 440° Fahr. Notwithstanding, however, this remarkable change, the analysis of the modified oil gave results closely coinciding with those of the original liquid, viz. a composition identical, in 100 parts, with that of olefiant gas.

These analyses were made in September 1835. In the Annalen der Pharmacie, October 1835, Professor Liebig has directed the attention of chemists to the remarkable alteration produced by sulphuric acid on the oil of caoutchouc; and has conjectured that the change consisted in the conversion of that oil into eupion, which resists sulphuric acid. If so, he proceeds, then it is possible that eupion may be only produced from the oil of tar by the action of the sulphuric acid employed in its preparation.

I cannot acquiesce in this view. The eupion of Reichenbach boils at 110° Fahr., and the oil alluded to at 440° Fahr.; moreover their odour is quite different: and if we are to admit them to be essentially the same, one of them must be in the highest degree impure, implying the presence of some other substance.

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.

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As M. Hess had previously shown that the pure oil of troleum 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 gas

Annales de Chimic, vol, Ixi.

331. p.

LXVII. Experimental Researches into the Physiology of the Human Voice. By JOHN BISHOP, Esq., &c. &c.

[Continued from p. 277, and concluded.]

THE HE falsetto, or voce di testa, has always been considered a most embarrassing subject of research, and its peculiar quality has excited the attention both of the physiologist and of the musician. The change produced in the voice when passing from the falsetto into the common tone, or the reverse, is in some persons very sensible to the ear, whilst in others it is almost imperceptible. It is remarkable that some individuals have the faculty of producing, in the same pitch, three or four tones, possessing either the falsetto or the common character, a circumstance which indicates that the difference between them depends rather upon an altered state of the vocal tube than upon any change in the glottis.

The falsetto has generally been ascribed to some particular adaptation of the upper ligaments of the larynx. Dodart * has attempted to prove that it is a supra-laryngeal function, and that the nose becomes the principal tube of sound instead of the cavity of the mouth. Bennati † also considers these tones to be modified by the supra-laryngeal cavity, an opinion not justified by the experiments which he has detailed.

According to this hypothesis, we must suppose the influence of the trachea to be entirely annulled; but on what acoustic principle this is to be effected he does not explain, nor indeed can any one else. The changes observed by him in the pharynx were undoubtedly associated with corresponding changes in the whole length of the tube, and all the phænomena he has described may thus be readily explained.

It was suggested to me by Mr. Wheatstone, that it was only necessary to suppose the vocal tube capable of subdividing its vibrating length to account for this peculiar character of tone. Analogous effects are observed in the clarionet, the flute, and other instruments; the change taking place at the twelfth of the fundamental note in the former instrument, and at the octave in the latter. Having had an opportunity of examining the phænomena in some individuals possessing remarkably fine voices, I placed my finger lightly on the larynx, and requested them to gradually elevate the voice from the primary to the falsetto tones, when, although the ear could scarcely distinguish

* Mém. de l'Acad., 1707.

+ Recherches sur le Mechan. de la Voix Hum.

the moment of transition, I found that, the larynx suddenly fell, and then continued to re-ascend as the tones became more acute. On observing the motions of the larynx in a mezzo-soprano voice, I found a double falsetto, consisting of several tones of each register, with the power of yielding either the primary or the falsetto character. In this case the larynx fell twice, but in a much smaller degree. An instance of this kind of voice occurs in Miss Lanza. At the moment the larynx falls, during the continued ascent of the tones, the column of air and the tube become divided into portions separated by nodes, yielding harmonics of the fundamental notes, and the modulations of the voice are regulated, as before, by the divided length and relative tension of the tube. A much smaller quantity of air is sufficient to produce these tones; consequently, public singers who chiefly employ the falsetto, suffer much less fatigue than those who use the primary notes.

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In conducting these observations, care must be taken that the voice do not ascend or descend the scale too rapidly, otherwise the effect may escape detection. In further confirmation of these views it may be remarked, that when the glottis is injured and silenced by disease, the voice is entirely annihilated, which could not be the case if there were any means of ducing sound by the superior ligaments of the larynx. There is, however, no doubt that the human voice derives a portion of its peculiar quality from the reverberations of sound in the cavities of the chest and head, modified by every change in these cavities as well as in the vocal tube. (The great effect produced by the nasal cavities on the voice is well known.)

Much pains have been taken by physiologists to find an analogy between the organs of voice and artificial musical instruments. Amongst those which have been selected for this purpose are the drum, the duck-whistle, the reed, and various other wind and stringed instruments. These attempts serve to illustrate the complicated structure and functions of the vocal organs; but it appears to me more simple, and at the same time nearer the truth, to consider them in the following point of view:

They consist of elastic membranes inclosed in a tube. The glottis is a most complex and beautifully constructed membranous vibrating apparatus, exquisitely adapted for producing all the tones of the voice. The vocal tube, or pipe, is adjusted on the most refined acoustic principles, to yield with the glottis isochronous vibrations.

The perfect adaptation of these organs, in a manner inimitable by mechanical art, to produce the most melodious sounds,