tion, where it is subject to a more uniformly elevated temperature than in the integument, is well known to be of a more suety character-that is to say, it contains a smaller proportion of olein, and has a higher melting point. These familiar facts point again to some importance in the animal econoniy, attaching to the melting point of the fat and the consequent degree of fluidity in which it should exist during life.

With regard to the fat of the integument-the principal deposit of adipose tissue in the body-it appears to me self-evident that the fluidity of this fat must vary with the temperature of the atmosphere in which the animal is placed; to what extent this is the case, is, in my opinion, a most important subject for enquiry, and although the experiments to determine the question are yet deficient, I hope soon to be able to supply them.

In conclusion, what I now suggest as a general proposition, is this:-That, in all probability, the stability of the fats of the animal body in resisting too rapid oxidation is dependent upon the degree of solidity which they possess at the temperature of the living animal at any given time; that alterations in external temperature may affect the solidity of the adipose tissue of the integument, and, consequently, its power of resisting oxidation; and that, therefore, in all probability, it is of great importance that the food of an animal shall contain a certain proportion of material capable of supplying the adipose tissue with solid fat.

The principal questions which I wish to submit to chemists, as requiring to be settled by their experiments, are the following:

filling all space is often regarded as equally certain with
the presence of a gaseous envelope surrounding our
globe.
The atomic theory and the hypothesis of an ethereal
medium are, at present, absolutely necessary, the one to
the progress of chemistry, the other to the further de-
velopment of physics; but neither this circumstance nor
the splendid discoveries made by their ad can establish
their truth. A mathematician starting from false data is
sure to arrive at a false result; but it is far otherwise
with theory, for false theories can, and constantly do,
conduct to true facts. Thus Columbus's counterpoise
theory of the earth led to the discovery of America,
although that theory was nevertheless essentially false.
The most sober worker in science cannot progress
without the assistance of thecry to co-ordinate his facts,
and to lead him on to further research. It is here that
even a false theory is invaluable, and it is only when the
theory continues to be held after it has become opposed
to facts that it exercises a prejudicial influence upon the
progress of science. Then it hinders rather than expe-
dites the advance of the experimenter, and ought to be
at once abandoned.

In pursuing the investigation forming the subject of this discourse, the speaker had been compelled thus to abandon a theory of the source of light in luminous flames, which he, in common with others, had derived from Davy's classical researches on flame.

Our text-books answer the question, What is the source of light in a luminous gas or candle flame? in the most positive and unanimous manner.

1. What is the relative facility for oxidation of the solid and liquid fats at similar and at different tem-lowing quotations may be made:peratures?

Selecting from some of the most celebrated, the fol

2. Is the facility for oxidation inversely as the melting points?

3. Is it the same for all fats at their melting points? 4. After the melting point of a fat has been attained, is the facility for oxidation affected by further increments of temperature?

5. Is there a temperature at which fa's cease to be oxidisable, and if so, what relation does this bear to the melting point in each instance?

84, Harley Street, Aug. 19, 1868.

"All our artificial lights depend upon the ignition of solid matter, in the intense heat developed by the chemical changes attendant on combustion."- W. A, Miller.

"Whenever hydrocarbons are imperfectly buint, there is a deposition of carbon, and this temporary deposition of carbon is an essential condition for the production of the white light required in an ordinary flame."— Williamson,

"The illuminating power of the gas flame is therefore due to these carbon particles, which are af erwards burned nearer the border of the flame.”—Balfour Stewart.

"The brightness or illuminating power of flame deON THE SOURCE OF LIGHT IN LUMINOUS pends not only on the degree of heat, but likewise on

FLAMES.*

BY PROFESSOR FRANKLAND, F.R.S.

THE most prolific source of error amongst mankind is the unquestioning acceptation of authoritative opinion. However much we may pride ourselves upon the sifting of the explanations of things by our own enlightened judgments, it cannot be denied that the ipse dixit mode of settlement is still wonderfully frequent amongst us. Not only is this the case with the public in general, but even the cultivators of science are not entirely innocent of the same weakness.

The essential difference between a fact and a theory is not always appreciated with sufficient vividness. The statement that "sixteen parts by weight of oxygen unite with two parts of hydrogen to form water," is considered by many, for instance, as perfectly synonymous with the assertion that " one atom of oxygen unites with two atoms of hydrogen to form water." The existence of an imponderable ethereal medium A Lecture delivered before the Royal Institution of Great Britain,

Friday, June 12, 1868.

the presence or absence of solid particles which may act as radiant points. A flame containing no such particles emits but a fecble light, even if its temperature is the highest possible."-Watts.

The speaker then proceeded to investigate a number of different flames: he showed that there are many flames possessing a high degree of luminosity which cannot possibly contain solid particles. Thus the flame of metallic arsenic burning in oxygen emits a remarkably intense white light; and as metallic arsenic volatilises at 180° C., and its product of combustion, arsenious arhydride, at 218° C., whilst the temperature of incandescence in solids is at least 500° C., it is obviously impossible here to assume the presence of ignited solid particles in the flame. Again, if carbonic disulphide vapour be made to burn in oxygen, or oxygen in carbo. ic disulphide vapour an almost insupportably brilliant light is the result; now fuliginous matter is never of sulphur (440 C.) is below the temperature of incanpresent in any part of this flame, and the boiling point descence, so that the assumption of solid particles in the flame is here also inadmissible. If the last experiment

be varied by the substitution of nitric oxide gas for oxygen, the result is still the same; and the dazzling light produced by the combustion of these compounds is also so rich in the more refrangible rays that it has been employed in taking instantaneous photographs, and for exhibiting the phenomena of fluorescence. Lastly, amongst the chemical reactions celebrated for the production of dazzling light, there are few which surpass the active combustion of phosphorus in oxygen. Now phosphoric anhydride, the product of this combustion, is volatile at a red heat,* and it is therefore manifestly impossible that this substance should exist in the solid form at the temperature of the phosphorus flame, which far transcends the melting point of platinum.

For these reasons, and for others which the speaker had stated in a course of lectures on "Coal Gas," delivered in March, 1867, and printed in the Journal of Gas Lighting, he considered that incandescent particles of carbon are not the source of light in gas and candle flames, but that the luminosity of these flames is due to radiations from dense but transparent hydrocarbon vapours. As a further generalisation from the above-mentioned experiments, he was led to the conclusion that dense gases and vapours become luminous at much lower temperatures than aëriform fluids of comparatively low specific gravity; and that this result is to a great extent, if not altogether, independent of the nature of the gas or vapour, inasmuch as he found that gases of low density, which are not luminous at a given temperature when burnt under common atmospheric pressure, become so when they are simultaneously compressed. Thus mixtures of hydrogen and carbonic oxide with oxygen emit but little light when they are burut or exploded in free air, but exhibit intense luminosity when exploded in closed glass vessels, so as to prevent their expansion at the moment of combustion.

under a pressure of fourteen atmospheres is very brilliant and perfectly continuous.

If it be true that dense gases emit more light than rare ones when ignited, the passage of the electric spark through different gases ought to produce an amount of light varying with the density of the gas; and the speaker showed that electric sparks passed as nearly as possible, under similar conditions, through hydrogen, oxygen, chlorine, and sulphurous anhydride, emit light, the intensity of which is very slight in the case of hydrogen, considerable in that of oxygen, and very great in the case of chlorine and sulphurous anhydride. On passing a stream of induction sparks through the gas standing over liquefied sulphurous anhydride in a strong tube at the ordinary temperature, when a pressure of about three atmospheres was exerted by the gas, a very brilliant light was obtained. A stream of induction sparks was passed through air confined in a glass tube connected with a condensing syringe, and the pressure of the air being then augmented to two or three atmospheres, a very marked increase in the luminosity of the sparks was observed, whilst on allowing the condensed air to escape, the same phenomena were observed in the reverse order. Way's mercurial light was also exhibited as an instance of intense light produced by the ignition of the heavy vapour of mercury.

The gases and vapours just mentioned have the following relative densities:

The feeble light emitted by phosphorus when burnIn a communication just made to the Royal Society ing in chlorine seems, at first sight, to be an exception the speaker had described the extension of these expe- to the law just indicated, for the densi y of the product riments to the combustion of jets of hydrogen and car- of combustion (phosphorous trichloride) 68-7 would bonic oxide in oxygen under a pressure gradually in- lead us to anticipate the evolution of considerable light. creasing to twenty atmospheres. These experiments, But it must be borne in mind that the luminosity of a which were conducted in the laboratory of the Royal flame depends also upon its temperature, and it can be Institution, were made in a strong wrought-iron ves- shown that the temperature in this case is probably sel furnished with a thick glass plate of sufficient size greatly inferior to that produced by the combustion of to permit of the optical examination of the flame. The phosphorus in oxygen. We have not all the necesappearance of a jet of hydrogen burning in oxygen un- sary data for calculating the temperature of these der the ordinary atmospheric pressure was exhibited. flames, but, according to Andrews, phosphorus burnt On increasing the pressure to two atmospheres, the in oxygen gives 5,747 heat units, which, divided by previously feeble luminosity was shown to be very the weight of the product from one grain of phosphomarkedly augmented, whilst at ten atmospheres' pres- rus, gives 2,500 units. When phosphorus burns in sure, the light emitted by a jet about one inch long was chlorine, it gives only, according to the same authoamply sufficient to enable the observer to read a news-rity, 2,085 heat units, which, divided as before by the paper at a distance of two feet from the flame, and this weight of the product, gives 470 units. It is therefore without any reflecting surface behind the flame. Ex- evident that the temperature in the latter case must be amined by the spectroscope, the spectrum of this flame greatly below that produced in the former, unless the is bright and perfectly continuous from red to violet. specific heat of phosphoric anhydride be enormously With a higher initial luminosity, the flame of car- higher than that of phosphorous trichloride. The bonic oxide in oxygen becomes much more luminous at speaker had, in fact, found that if the temperature a pressure of ten atmospheres than a flame of hydrogen of the flame of phosphorus, burning in chlorine, be of the same size and burning under the same pressure. raised about 500° C. by previously heating both eleThe spectrum of carbonic oxide burning in oxygen ments to that extent, the flame emitted a brilliant white light.

Davy mentions this fact in connection with his view of the source of luminosity in flames, and endeavours to explain the, to him, anomalous phenomenon. He says:-"Since this paper has been written, I have found that phosphoric acid volatilises slowly at a strong red heat, but under moderate pressure it bears a white heat; and in a flame so intense as that of phosphorus, the elastic force must produce the effect of compression."-Davy's Works, vol. vi, p. 48.

To return to ordinary luminous flames, the argument of the necessity of solid particles to explain their luminosity obviously falls to the ground; and a closer examination into the evidence of the existence of these Soot from a particles reveals its extreme weakness.

gas flame is not elementary carbon, it always contains

1

CHEMICAL NEWS,

CHIC Absorption of Gases by Charcoal.-Researches on the Ethers.

Nov., 1868.

239

He considered that the ultimate particles of gas rested as strata or layers in the charcoal; the nearer particles were, therefore, less forcibly held than the more distant. They were also most difficult to remove. If this physical action had an analogy with chemical action, it would also partially throw light upon it, and it seemed to point to compounds containing parts held together more or less loosely than other parts. The gas and charcoal form such a compound already in a sense not purely chemical.

hydrogen. The perfect transparency of the luminous portion of flame also tends to negative the idea of the presence in it of solid particles. The continuous spectrum of gas and candle flames does not require, as is commonly supposed, the assumption of solid particles. The spectra of the flames of carbonic oxide in the air, of carbonic disulphide, arsenic, and phosphorus in oxygen, are continuous, and so, as we have seen, is that of hydrogen burning in oxygen under a pressure of ten atmospheres. It is to the behaviour of hydrocarbons under the influence of heat that we must look The numbers, however, require analysis and careful for the source of luminosity in a gas flame. These gra- thought. Two of them seem very remarkable-namely, dually lose hydrogen, whilst their carbon atoms coa- oxygen and carbonic acid, as the volumes are exactly lesce to form compounds of greater complexity, and those of the weights of oxygen in water and an atom of consequently of greater vapour density. Thus marsh-carbonic acid. Eight volumes of oxygen are 128 times gas (CH) becomes acetylene (C2H2), and the density heavier than one volume of hydrogen; the gases, thereincreases from 8 to 13. Again, olefiant gas (CH) fore, do not seem to be taken up according to their forms naphthaline (CioHs), when the vapour density atomic weights. By attention to this, he hoped that augments from 14 to 64. These are some of the dense some light would be thrown on the atomic physical hydrocarbons which are known to exist in a gas constitution of bodies. flame, but there are doubtless others still more dense; pitch, for instance, must consist of the condensed vapours of such heavy hydrocarbons, for it distils over from the retorts in the process of gas-making. Candle flames are similarly constituted. The direct dependence of the luminosity of gas and candle flames upon atmospheric pressure, also strongly confirms the view that the light of these flames is due to incandescent dense vapours.

This inquiry cannot be confirmed to terrestrial objects. Science seeks alike for law in the meanest and grandest objects of creation. From questioning a candle she addresses herself to suns, stars, nebulae, and comets; the same considerations which have just been applied to gas and candle flames are equally pertinent to these great cosmical sources of light.

ON

In a practical point of view, he hoped to gain by the enquiry some knowledge of the phenomena of spontaneous combustion to which several substances are subjected.

Experiments on the absorption of mixed gases had been made, but were left for description when the paper was written, and also those on the extrusion of the gas by another.

He had a very long time ago illustrated the oxidising power of porous substances in reports to the British Association, perhaps so long ago that some persons thought it needful to do it again. No one, however, had succeeded so thoroughly as Dr. Stenhouse in this department.

Experimnets on salts were not sufficiently telling, and a better mode of making them required to be found; but it was clear to him that the charcoal took up most readily those oxides the metals of which were less inclined to oxidise. The combinations being

THE ABSORPTION OF GASES BY CHARCOAL.* weaker, the bases were removed from the acid, a

BY DR. R. ANGUS SMITH, F.R.S.

He

DR. ANGUS SMITH, without reading a paper, said that he
had somewhat farther extended his inquiries into the
laws of absorption of gases, as shown by charcoal. He
had some years ago said that he believed the actions
were on the border between chemistry and physics, or
that physical phenomena were an extension of the
chemical. Last year, in a short note, he said that the
gases which he tried were absorbed in whole volumes,
or volumes which were multiples of hydrogen.
had now tried other gases, with the following results:-
Hydrogen, 1; oxygen, 7'99; carbonic oxide, 603; car-
bonic acid, 22.05; marsh gas, 1001; nitrous oxide, 12'90;
sulphurous acid, 3695; common air, 40063. Nitrogen
was found to be 4:27; probably this is a little too low,
as there is always some nitrogen left in the heated
charcoal. These numbers are got by dividing the num-
ber of volumes absorbed by each gas by the volumes of
hydrogen absorbed. They are an average of many.
The numbers, in some cases, differ considerably; it is
supposed that the reason lies in the constitution of the
charcoal, but some of it may lie in the mode of working.
It seemed to him important to bring under some form
of order those long observed but irregular actions which
seemed little capable of being shown to be guided by a
law; what that law is he did not see fully, but there
distinctly was order.

struggle against chemical action existing. In other words, an action with little chemical character opposed itself to the purely chemical, and by aid of mass gained something, a phenomenon which is frequent whenever chemical action is weak, and one which interferes much with exactness in analysis.

RESEARCHES ON THE ETHERS.*

BY J. ALFRED WANKLYN,

PROFESSOR OF CHEMISTRY IN THE LONDON INSTITUTION.

FIVE cubic centimetres of good acetate of ethyl and 0.3 gramme of sodium were sealed up in a small glass tube, and then heated in the water-bath to 100° Č. until all the sodium had disappeared. The tube was then opened under water, and the gas which escaped measured 25 c.c. at the ordinary temperature of the air. Corrected at o° C. and 760 m.m. pressure (dry), the volume of the escaped gas is about 23 c.c. If the volume of hydrogen which is equivalent to 0.3 gramme of sodium be calculated, it will be found to be about 140 c.c.

Therefore, this experiment establishes the fact that there is no evolution of hydrogen as a main product of the action of sodium on acetic ether. Moreover, the 23 c.c. of gas which escaped must be regarded as due

* British Association, Norwich Meeting, Section B. Communicated by the Author.

* British Association, Norwich Meeting, Section B.

were sealed up and heated very gently in the water-ther, and "Ethylic-sodacetone-carbonate," by Frankbath, and shaken up well during the progress of the reland and Duppa. action. The sodium dissolved without any evolution of gas. The experiment was repeated with the same result.

forming the new compound. The following is a tabu- and expose it to the direct action of the solar rays, it lar statement:

wherein the three equivalents of acetyl are fused together to constitute a non-atomic tri-acetyl, C.H.O.. Hydride of tri-acetyl, which is very well described by Geuther, is obtained by decomposing sodium tri-acetyl with glacial acetic acid, and is an oily liquid rather heavier than water; I have prepared some of it. The decomposition noticed by Geuther which it undergoes in contact with strong acids or alkali s, and in which the elements of water are taken up, is very interesting:

CH2O
C2H2O
C2H2O
H

+ H2O =

Acetone.

Alcohol.

The formation of alcohol in this reaction is a virtual conversion of acetic acid into alcohol, inasmuch as the tri-acetyl came from acetic acid.

All the compounds mentioned in Frankland and Duppa's paper as derived directly from acetic ether and sodium admit of representation as sodium-triacetyl, and products derived from sodium-triacetyl, as I will explain on another occasion.

will be observed that, while the chlorine solution is still yellow, the chloride of silver remains perfectly white; but afterwards, the chlorine solution becomes colourless and clear, and the chlorine decomposes the water under the action of light. As soon as the chloride of silver blackens at the surface it should be agitated from time to time, and left exposed for a few days to direct light until the whole becomes of a fine black colour.

Now take the tube into a dark place, and you will see the blackness disappear by degrees, chloride of silver becomes reformed, and the contents of the tube become perfectly white, although its structure is evidently dif ferent to what it was previous to its exposure to light. Then we may expose it afresh to the sun, and after it has again become black we can make it white again, and this experiment can be repeated indefinitely, and is an evidence that in those successive reactions the chlorine, oxygen, hydrogen, &c., preserve their properties of combination and recombination. These gases manifest the properties which we, in France, call the mascent condition-properties certainly electric, and which only in certain circumstances become evident, but which, without doubt, exist in all bodies when the circumstances are favourable. We have plenty of examples in connection with oxygen, hydrogen, and similar bodies. There is one special and striking example in the experiment which ought to be mentioned. place chloride of silver in a thin and fine tube, one millimetre internal diameter, and close it at one end, this little tube being placed in the larger one, its chloride becomes dark under the action of light, but once dark it remains always black, whilst its neighbour, under the alternate action of light and darkness, blackens and bleaches, a manifest evidence of the molecular movements induced by the light upon the chloride of silver when surrounded by a suitable liquid.

If we

It is easy to comprehend the value of the knowledge of this property in photography. We see with what care we ought to get rid of our enemy, hydrochloric acid, from our sensitive papers; to dry them perfectly, and to deprive them of all hygrometric salts, for without doubt the image, especially the darker portions, will be liable to the decomposition and recomposition above described.

Bromide of silver presents the same properties and the same effects; but it is necessary, in order for the bromide salt to become colourless, that a longer exposure should be given. With respect to the iodide of silver, there are special conditions requisite, and I have only been able to cause this salt to blacken in the sun after having sensitised it by means of pyrogallic acid.It does not blacken visibly without a reducing agent. It would be especially interesting to know if the cyanide

ON A PECULIAR ACTION OF LIGHT UPON of silver would behave in a similar manner in the pres

THE SALTS OF SILVER.*

BY PROFESSOR MORREN.

ence of cyanogen; but I have not had time to make this experiment, but I hope to be able to record it at another meeting of the Association.

BY PHILIP HOLLAND.

THE molecular movements produced under the action of light present special interest, and in order to show THE MEASUREMENT OF GASES OVER WATER. my sympathy with this Association I present the results of some experiments, although they are at present not completed. The facts are these:-If in a tube of white glass from 14 to 15 inches long, and from 1 to 2 inches in diameter, you enclose moist chloride of silver freshly precipitated by means of a solution of chlorine in water,

* British Association, Norwich Meeting, Section A.

In an article on this subject in CHEMICAL NEWS for July 3 (Am. Reprint, Sept., 1868, page 113), I proposed the adoption of Erdmann's float to be used with the graduated tube when reading off a volume of gas over water. The chief advantage claimed for it is that the operator is enabled readily to appreciate differences of a tenth of a