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3. Chemical Parentage of the Spectrum under discussion.-I freely admit the force of Professor Piazzi Smyth's remarks on the difficulty of volatilizing carbon ; but that does not appear to me to affect the experimental evidence for my assertion that “this spectrum is the spectrum of carbon, and not of a hydrocarbon or any other compound of carbon.” That evidence is very simple; this spectrum can be obtained alike from compounds of carbon with hydrogen, with nitrogen, with oxygen, with sulphur, and with chlorine.

Whether or not the spectrum is produced by the vapour of carbon is another question; but if this spectrum is, as Professor Piazzi Smyth asserts, that of a hydrocarbon, will Professor Piazzi Smyth explain how it is possible to obtain it from cyanogen, a compound of carbon and nitrogen, when no hydrogen is pre sent? I have just repeated the experiment with cyanogen for perhaps the fiftieth time. Dry mercuric cyanide was heated in a test-tube, and the gas evolved was dried by passing through a tube containing phosphoric anhydride; it then passed through a tube provided with platinum wires, the end of which dipped below warm and dry mercury. On passing the discharge from an induction-coil between the platinum wires a spark was obtained which gave the spectrum in question brilliantly, the gas being decomposed and carbon being deposited.

Professor Piazzi Smyth says that in May 1871, in a paper sent to the Royal Astronomical Society, he “ gave

such extracts from the authorities on either side as showed that the spectroscopists declaring for pure carbon, in opposition to those pronouncing for carbohydrogen, were blundering little less than the perpetual-motion men of last century." Permit me to quote from a paper communicated by myself to the Journal of Science for January 1871:

“At first sight it would appear that carbon is an element unlikely to yield a discontinuous spectrum, inasmuch as it is not known in the gaseous condition; and that if we obtain discontinuous spectra from carbon compounds, they must be due to some compound of carbon.

carbon. Thus the bright blue lines observed by Swan (1856) in the spectrum of the Bunsen-flame might be supposed to be more probably due to carbonic oxide or carbonic acid than to carbon itself. But we find that these same lines occur not only in the spectrum of the flame, but also in the spectra obtained by passing the electric spark either through carbonic oxide, or olefiant gas, or cyanogen, and the lines thus found to be common to compounds of carbon with different elements must of course be due to carbon itself. Whether they are really produced by carbon in the gaseous state is a question which cannot yet be certainly decided. If the carbon is in the solid

state, we shall then have an exception to the law that incandes-
cent solids give continuous spectra, of which we have only one
other example, viz. the spectrum of bright lines obtained by Bahr
and Bunsen from glowing erbia. In the case of erbia it is not
impossible that the bright lines are really produced by a gas
(Huggins and Reynolds, Proc. Roy. Soc. June 16, 1870); and
it is by no means improbable that, when a hydrocarbon is burned
it is first of all decomposed into its elements, which then com-
bine with oxygen. If this be so, the carbon may exist for the
moment in the gaseous state.”

The difference to which Professor Piazzi Smyth calls attention
between the spectra of compounds and elements (the difference,
namely, between Plücker's “spectra of the first order” and
“spectra of the second order") is important. It is perfectly
true that the spectrum of carbon is a spectrum of the first order,
and would, from that evidence, be inferred to be the spectrum of
a compound. If, however, this spectrum be caused by a com-
pound, it can only be a compound of carbon with carbon.

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XIV. Note on the Spectrum of Carbon. By Dr. ATTFIELD,

Professor of Practical Chemistry to the Pharmaceutical Society
of Great Britain.
To the Editors of the Philosophical Magazine and Journal.

GENTLEMEN,
IN
Nchemistry, when compounds of an element with dissimilar

radicals yield similar reactions with a reagent, the reactions
are held to be evidence of the presence of the element, even though
that element in its free state be a massive metal and those com-
pounds be liquid or even vaporous or gaseous. At least, to
the question “who gainsays the deduction ?” the answer is,
at present, no one.

In 1862 I showed that gaseous or vaporous compounds of car, bon with dissimilarradicals, when ignited by the aid of the chemical force in flames, or by the electric force in tubes, or in certain cases by either force, yielded identical spectra; and therefrom I inferred that the spectrum was that of carbon, though I could not say whether the carbon was free or combined in the gases and vapours. And who gainsays the deduction ? Mr. Piazzi Smyth, Astronomer Royal for Scotland, in the current Number of the Philosophical Magazine (January 1875).

Mr. Piazzi Smyth regards my deduction as a delusion, a blunder, an egregious error, a myth, a mistake patronized, he says, by the Royal Society through secret committees, which he designates accursed things, acting occasionally "as very dragons to keep out any salutary doubt expressed on a favoured topic."

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These are strong terms, especias via passed by a Atronomer Royal, and with the deüberaba prired sige atas stances of serial publication. Very strong przetaericoce obtained by himself would surely scarves as 22 Asroopet Royal in the employment of soch terms. Ta 'vibe ben lieved ?) not a tittle of such evidence is crioca. Nas, be spectrum which I stated to be that of carbon, a statemezi A. firmed over and over again by emitent ciemists and pèsests (Plücker, Morren, Marshall Waits), Mr. Piazzi Smyth asserts is not only not that of carbon, but solely teat of a hydrocarbon again an assertion unsupported by any experimental evidence whatever. It is true that Mr. Smyth quutes Lielegg and Crookes against me. But Lielegg supports me, and Croses is cited be cause of an editorial footnote in the 'Chemical News' appended to a notice of Morren's paper, asking experimentalists what they meant by the "vapour of carbon " existing in a flame. As for Lielegg, I will quote without comment the last sentence but one of his paper (Eng. trans. in Phil. Mag. March 1869, p. 216:“Therefore tubes filled with combinations of carbon and hydr. gen show the lines of carbon and those of bydrogen ; tubes filled with carbonic oxide or carbonic acid gas sbow those of carbon and oxygen, giving, in fact, a spectrum of carbon, because the extremely small pressure and the high temperature cooperate in reducing the carbon to a gaseous condition.” Plücker, who, with Faraday, General Sabine, and Geissler, spenttwoor three hours with me at the Royal Institution minutely examining my spectra--Plücker afterwards writes, on Nov. 12, 1862: “ Je suis d'accord avec vous sur l'existence du spectre de la vapeur de carbone.” Morren says, on page 6 of the paper already mentioned, "Je me mis donc au travail avec la pensée préconçue de combattre l'assertion émise par le savant anglais; mais il résulte, au contraire, des expériences auxquelles je me suis livré, que M. Attfield a raison, et que c'est bien la vapeur du carbone qui donne le spectre indiqué plus haut.”.

I might just refer to some minor statements made by Mr. Piazzi Šmyth. He says, in a paper to which he draws attention as not having been accepted, as he desired, by the Roysl Astronomical Society, but afterwards printed in the 'Observations' of his own observatory, that the question put by Crookes was never answered. I answered it at once, and the reply was inserted in the Chemical News' a fortnight after the question was asked. I did not work "in a rich London laboratory." With ordinary induction-coils, borrowed, the one from a captain in the army,

the other from Mr. Gassiot; with a spectroscope which Dr. Frankland would scarcely now own; with tubes and apparatus made by my own bands, and made, I believe chemically clean; and by the aid of well-fitting shutters in an ill-fur

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state, we shall then have an exception to the law that incandescent solids give continuous spectra, of which we have only one other example, viz. the spectrum of bright lines obtained by Bahr and Bunsen from glowing erbia. In the case of erbia it is not impossible that the bright lines are really produced by a gas (Huggins and Reynolds, Proc. Roy. Soc. June 16, 1870); and it is by no means improbable that, when a hydrocarbon is burned it is first of all decomposed into its elements, which then combine with oxygen. If this be so, the carbon may exist for the moment in the gaseous state.”

The difference to which Professor Piazzi Smyth calls attention between the spectra of compounds and elements (the difference, namely, between Plücker's “spectra of the first order” and “spectra of the second order”) is important. It is perfectly true that the spectrum of carbon is a spectrum of the first order, and would, from that evidence, be inferred to be the spectrum of a compound. If, however, this spectrum be caused by a compound, it can only be a compound of carbon with carbon.

XIV. Note on the Spectrum of Carbon. By Dr. ATTFIELD,

Professor of Practical Chemistry to the Pharmaceutical Society of Great Britain. To the Editors of the Philosophical Magazine and Journal.

GENTLEMEN, IN Nchemistry, when compounds of an element with dissimilar

radicals yield similar reactions with a reagent, the reactions are held to be evidence of the presence of the element, even though that element in its free state be a massive metal and those compounds be liquid or even vaporous or gaseous. At least, to the question “who gainsays the deduction ?” the answer is, at present, no one.

In 1862 I showed that gaseous or vaporous compounds of carbon with dissimilar radicals, when ignited by the aid of the chemical force in flames, or by the electric force in tubes, or in certain cases by either force, yielded identical spectra; and therefrom I inferred that the spectrum was that of carbon, though I could not say whether the carbon was free or combined in the gases and vapours. And who gainsays the deduction ? Mr. Piazzi Smyth, Astronomer Royal for Scotland, in the current Number of the Philosopbical Magazine (January 1875).

Mr. Piazzi Smyth regards my deduction as a delusion, a blunder, an egregious error, a myth, a mistake patronized, he says, by the Royal Society through secret committees, which he designates accursed things, acting occasionally was very dragons to keep out any salutary doubt expressed on a favoured topic.”

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ever.

These are strong terms, especially when penned by an Astronomer Royal, and with the deliberation involved in the circumstances of serial publication. Very strong experimental evidence obtained by himself would surely scarcely justify an Astronomer Royal in the employment of such terms. Yet (will it be believed ?) not a tittle of such evidence is forthcoming. Nay, the spectrum which I stated to be that of carbon, a statement confirmed over and over again by eminent chemists and physicists (Plücker, Morren, Marshall Watts), Mr. Piazzi Smyth asserts is not only not that of carbon, but solely that of a hydrocarbon again an assertion unsupported by any experimental evidence what

It is true that Mr. Smyth quotes Lielegg and Crookes against me. But Lielegg supports me, and Crookes is cited because of an editorial footnote in the 'Chemical News' appended to a notice of Morren's paper, asking experimentalists what they meant by the “vapour of carbon” existing in a flame. As for Lielegg, I will quote without comment the last sentence but one of his paper (Eng. trans. in Phil. Mag. March 1869, p. 216:“Therefore tubes filled with combinations of carbon and hydrogen show the lines of carbon and those of hydrogen ; tubes filled with carbonic oxide or carbonic acid gas show those of carbon and oxygen, giving, in fact, a spectrum of carbon, because the extremely small pressure and the high temperature cooperate in reducing the carbon to a gaseous condition." Plücker, who, with Faraday, General Sabine, and Geissler, spent twoor three hours with me at the Royal Institution minutely examining my spectra-Plücker afterwards writes, on Nov. 12, 1862: “Je suis d'accord avec vous sur l'existence du spectre de la vapeur de carbone.” Morren says, on page 6 of the paper already mentioned, “Je me mis donc au travail avec la pensée préconçue de combattre l'assertion émise par le savant anglais; mais il résulte, au contraire, des expériences auxquelles je me suis livré, que M. Attfield a raison, et que c'est bien la vapeur du carbone qui donne le spectre indiqué plus haut."

I might just refer to some minor statements made by Mr. Piazzi Šmyth. He says, in a paper to which he draws attention as not having been accepted, as he desired, by the Roysl Astronomical Society, but afterwards printed in the Observations of his own observatory, that the question put by Crookes was never answered. I answered it at once, and the reply was inserted in the Chemical News' a fortnight after the question was asked. I did not work “in a rich London laboratory." With ordinary induction-coils, borrowed, the one from a captain in the army, the other from Mr. Gassiot; with a spectroscope which Dr. Frankland would scarcely now own; with tubes and apparatus made by my own bands, and made, I believe chemically clean ; and by the aid of well-fitting shutters in an ill-fur

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