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The saturation of these two units by the trivalent nitrogen atom left 3-2 = 1 attraction unit disengaged; in a similar manner, if the saturation be effected by the quadrivalent carbon atom, 4-2 = 2 attraction units must remain un

saturated.

cated whiskee," "pure Islay mountain," "Indian tinc-a molecule involves the liberation of two attraction units. ture," and "red currant cough elixir," the exciting principle of all of which was found to be hyponitrous ether prepared from methylated spirit. The above compounds were all highly stimulating, and it would appear that they are consumed by some of the poor, because they produce intoxication at the cost of only a few pence, The reason why the carbon atom, when fixed by comwhilst there are good reasons for believing that hypo- pounds, associates with two atoms of hydrogen,-why so nitrous ether itself, and in some parts of Ireland even large a number of carbon compounds differ by CH,, or a multiple thereof,-in fact, the relation in the composition sulphuric ether, are used by the needy classes for the of numerous series of carbon compounds which is desigsame object. It is difficult to see how this evil, so per-nated by the term homology is now intelligible. nicious to the moral and physical welfare of those who indulge in it, can be checked, as the substances under consideration possess more the character of medicines than of ordinary spirits, and may thus be legally kept and sold by any chemist.

During the year 139 samples of wood spirit were examined, the object being to ascertain that they were free from vinous alcohol, and suitable for methylating spirits of wine.

Miscellaneous Samples. — Under this head 217 samples have been analysed, including spirits, wines, cherry and raspberry brandies, medicated compounds, cane and starch sugars, molasses, treacle, methylated spirits, "Finish," vinegar, chocolate, cocoa, caramel, and cyder.

Total Number of Samples Analysed in the Laboratory in each of the Years 1862, 1863, and 1864.

Description of Samples.

Number of Samples examined in

In attempting to illustrate this behaviour of the carbon atom by our mechanical models, we conveniently select the molecule of marsh gas, the simplest compound of carbon and hydrogen, as the foundation of our edifice. This molecule we open for the insertion of a second carbon atom. The two attraction units liberated by the rupture of the molecule are saturated by two of the attraction units of the quadrivalent carbon atom, two attraction units of which remain unsaturated. Indeed, two carbon arms remain uncovered, on which we forth with fasten two atoms of hydrogen. The transformation of marsh gas into hydride of ethyl is thus accomplished.

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Beer, and substances used in

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ROYAL, INSTITUTION OF GREAT BRITAIN.
Weekly Evening Meeting, Friday, April 7.

H.R.H. THE Prince of Wales, Vice-Patron, in the Chair.

On the Combining Power of Atoms,

By Dr. A. W. HOFMANN, F.R S.
(Continued from page 179.)

THE experience acquired in the study of the oxygen and
nitrogen compounds has prepared us for the examination
of the increment of carbon. In fact, it is only necessary
to apply the method hitherto followed to one of the series
of carbon compounds already reviewed to enable us to
understand why the carbon atom is assimilated, not atom
by atom, like the oxygen atom, not associated with one
atom of hydrogen like the nitrogen atom, but associated
with two atoms of hydrogen.

We have only to remember that the carbon atom saturates four combining units, while the nitrogen atom satu

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rates only three. Now, we have seen that the rupture of HYDRIDE OF ETHYL.

H

H

HYDRIDE OF PROPYL

Hydride of propyl, by the accession of a fourth carbon | chemical edifices, it is because I want to show you that atom, is converted into hydride of butyl.

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our building stones are available for many other purposes.

Hitherto we have been satisfied with examining under what conditions the atoms of oxygen, of nitrogen, and carbon are received into molecular structures. The question now presents itself, On what terms the chlorine atom is allowed to join?

The model of the marsh-gas molecule is still before us. Let us open this molecule for the reception of a chlorine atom. Two attraction units are thus liberated; but the chlorine atom is univalent. Accordingly two atoms of chlorine are required, one of which combines with the hydrogen atom which we remove from the marsh-gas, converting it into hydrochloric acid which separates, while the other chlorine atom joins the rest of the molecule of marsh-gas. The new molecule, monochlorinetted marsh-gas, may be looked upon as marsh-gas, in which one atom of chlorine holds the position originally occupied by the hydrogen atom. We are thus led up to the recognition of new conditions of combination-conditions which have not as yet attracted our attention this evening, but which unfold to us one of the most important principles of modern chemistry, the principle of substitution The monochlorinetted marsh-gas, which is a liquifiable gas, when again submitted to the action of chlorine loses a second, a third, and lastly, a fourth atom of hydrogen in the form of hydrochloric acid, giving rise to the formation of dichlorinetted, trichlorinetted marsh-gas, better known as chloroform, and, lastly, of tetrachlorinetted marsh-gas or tetrachloride of carbon, i.e., marsh-gas in which the four atoms of hydrogen are displaced by an equal number of chlorine atoms (Fig. 18).

FIG. 18.
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Our information regarding the combining powers of atoms is thus materially expanded. Having already learnt that when entering into a molecular structure the carbon atom associates with two atoms of hydrogen, the atom of nitrogen with one atom of hydrogen, that the oxygen atom combines directly, we now find that the chlorine atom combines only by substitution, i.e., when a space has become vacant in the molecule by the expulsion of hydrogen. The rest of the marsh-gas molecule remaining after the introduction of one atom of chlorine, and consisting of one atom of carbon, combined with three atoms of hydrogen, is frequently designated by the name of methyl. The aggregate of atoms CH,, the radical methyl, may be traced in all the compounds obtainable from marsh-gas by the insertion of other atoms. Thus, by the assimilation of an oxygen atom, marsh-gas becomes methylic alcohol, i.e., water in which one atom of hydrogen is displaced by methyl, by the absorption of nitrogen with its tributary hydrogen, it becomes methylamine, i.e., ammonia in which one atom of hydrogen is displaced by methyl; by the incorporation of an atom of carbon, lastly, with its pair of hydrogen atoms, the marsh-gas molecule is converted into methyl-marsh-gas, i.e., marsh-gas in which an atom of hydrogen is displaced by methyl.

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At one time the exertions of chemists were anxiously directed to the isolation of the atomic aggregate CH,. of the radical methyl (Fig. 19), from one or other of the methylic bodies just enumerated. The facility with which the chlorine atom in chloride of methyl may be exchanged for other atoms, leaving the aggregate of carbon and hydrogen, which we call methyl, perfectly intact, the mobility of one of the hydrogen atoms in methylic alcohol, and of two of the hydrogen atoms in methylic ammonia, the possibility of replacing even the oxygen and the nitrogen in these compounds, without affecting the methyl, the stability, lastly, of methylic marsh-gas, containing as it does the whole of its carbon and the whole of its hydrogen in the form of methyl, all these circumstances appeared to indicate the probability of the separate existence of methyl. Why all attempts to separate the atom group CH, have remained unsuccessful; why methyl could not be caught; why, ultimately when Dr. Frankland's masterly experiments appeared to have precluded all chance of escape, despairing methyl combined with itself, surrendering as methylic marsh-gas or methylmethyl; why, in fact, it would appear to be an essential character of methyl not to have a separate existence: all these questions are readily answered by our croquet balls,

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which exhibit us methyl as an unfinished molecule, capable of conversion into the finished molecules, hydride, chloride, hydrate, amide and methide of methyl, but not capable of existing as a molecular fragment with imperfectly balanced attractions.

Taking a farewell glance at the results we have elicited this evening, we may fairly ask whether the experience collected on a comparatively limited area is fully and unequivocally corroborated by the examination of a more expanded range of observations? To this question we cannot unhesitatingly give an affirmative answer. It would not be difficult to quote a number of substances, the construction of which appears to have been governed by rules of combination different from those which we have endeavoured to lay down. Indeed, we need not even go beyond the circumscribed field on which we have hitherto moved to meet with prominent cases of exception.

Among the several compounds of carbon and hydrogen which have passed through our hands this evening, we remember the two simplest, marsh-gas and olefiant gas. In the marsh-gas molecule CH4, we have the carbon atom completely saturated with hydrogen; by the entrance of a second carbon atom, with its two accessory hydrogen atoms, we saw the molecule of marsh-gas, or hydride of methyl, converted into the molecule of hydride of ethyl C2H.

The formula of olefiant gas, C,H,, places its molecule midway between the molecules of marsh-gas and hydride of ethyl. Comparing olefiant gas with marsh-gas, we find that it contains one of carbon more than the latter, the number of hydrogen atoms being equal in both substances. Contrary, then, to the rule on which we hitherto relied, we find that the carbon atom, transforming the marsh-gas molecule into the molecule of olefiant gas, enters without carrying along the two atoms of hydrogen, which we had accustomed ourselves to consider as the inseparable companions of the carbon atom on such occasions. While frankly admitting that in olefiant gas we meet with the first exception to a rule hitherto unbroken, we are entitled to inquire whether there are no means of explaining this anomalous construction of the olefiant gas molecule. Let us again apply to the models which, in a measure, have assisted us in constructing the rule; perhaps they may help us also in elucidating the exception.

In building up the molecule of olefiant gas by the insertion into the marsh-gas molecule of one atom of carbon only, we obtain what hitherto we would have called an unfinished molecule,-i.e., a molecule in which two of the attraction units of the second carbon atom are unsatisfied. Indeed, a glance at our model shows us that two carbon arms project uncovered. We are thus led to inquire whether unfinished molecules-i.e., molecules in which a certain number of attraction units remain unbalanced-are

AMIDE OF METHYL.

METHIDE OF METHYL.

capable of a separate existence. This question is accessible to experiment. Olefiant gas, indeed, possesses all the characters which, granting for argument's sake the possibility of its existence, we are inclined to attribute to an unfinished molecule. In the cases hitherto considered, we saw the chlorine atom, when admitted into a molecular structure, always entering with substitution, hydrogen separating from the chlorinetted molecule in the form of hydrochloric acid. In this manner we succeeded in transforming the marsh-gas molecule successively into monochlorinetted, di-, tri-, and, lastly, tetrachlorinetted marsh-gas or tetrachloride of carbon. Submitting, on the contrary, olefiant gas to the action of chlorine, we find that the chlorine is fixed directly, without substitution, the chlorine atoms meet, FIG. 20.

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so to speak, with vacant spaces existing in the olefiant gas molecule; in order to get in, they need not expel a corresponding number of hydrogen atoms to make room for them. The compound generated is the so-called Dutch liquid, an oily substance first produced by an association of Dutch chemists at the close of the last century. It was the production of this oily liquid that gave rise to the name of olefiant gas. The number of chlorine atoms thus received directly without substitution is two, corresponding exactly with the number of attraction units that remained unsaturated. Any further number of chlorine atoms are found to enter by substitution, and by substitution only. Similar phenomena are observed when olefiant gas is brought into the presence of bromine. We have here a large glass vessel containing some bromine and water; the vessel, by means of a flexible tube, is connected with a gas-holder filled with olefiant gas. On agitation, we see the olefiant gas rushing into the vessel as into a vacuum. The olefiant

gas fixes two atoms of bromine, being converted into a transparent colourless liquid, the substance called dibromide | of olefiant gas. Here, again, the combination takes place without substitution.

The behaviour of olefiant gas, under the influence of chlorine and bromine, elucidates the nature of its molecule. The facility with which this gas is capable of fixing two atoms of chlorine to become Dutch liquid, two atoms of bromine to become bromide of olefiant gas, and by roundabout processes two atoms of hydrogen to become hydride of ethylall three finished molecules-characterises olefiant gas as a molecule interrupted in its growth, and in which the power of resuming this growth, and the limit of its final develop. ment may be traced by the simplest experiments. The apparently anomalous construction of the olefiant gas molecule is thus most satisfactorily accounted for. Indeed, far from disturbing the harmony of the rules of combination elicited by our inquiries, a closer examination into the nature of this compound, whilst explaining whatever appeared exceptional in its construction, leads us, on the contrary, to a loftier interpretation of these rules, to the conception of compounds, the very structure of which foreshadows the more prominent features of their chemical character.

I have selected olefiant gas as an example of a class. We remember that this substance is the first term of a long list of homologous bodies, in all of which we find similar structure combined with similar chemical properties. All these substances, and, let me add, a great variety of others, we have to regard as molecules arrested under special circumstances at a certain stage of their development, but capable, under favourable conditions, of growing again, until by the perfect balance of the atomic attractions within they have ultimately arrived at maturity.

We have thus been led, step by step, to a distinction of a novel kind, that of finished and unfinished molecules; or, to use the more frequently employed expression, that of saturated and non-saturated compounds. I need not tell you that this distinction carries us to the threshold of a new field of research, hitherto crossed only by a small band of fearless pioneers, who are encountering difficulties on all sides. Admitting, as we are compelled to do, the existence of what we have called unfinished molecules, we inquire under what special conditions, at what special stages the growth of a molecule may be arrested. How is it that as yet the marsh-gas molecule is known only in the finished state, CH4, that none of the fragmentary marsh-gases, CH3, CH2, and CH1, which might exist, have ever been obtained? Again, how is it that the molecule of hydride of ethyl exists, so to speak, finished and unfinished; and, lastly, that of the several fragmentary states in which this molecule might be met with, two onlynamely, the two states C2H, (olefiant gas), and C2H2 We are thus (acetylene)-have ever been observed?

brought face to face with some of the most deeply interesting problems of chemical mechanics, in the solution of which the exertions of chemists are engaged at the present moment. I must not, however, dwell upon the interest attached to this new line of inquiry, upon the numerous experiments which the idea of saturated and non-saturated compounds has already suggested, and on the influence it is likely to exercise on the direction of chemical investigation for some time to come.

tion so kindly bestowed on my remarks will not, I trust, have been entirely thrown away if I have succeeded in convincing you that modern chemistry is not, as it has so long appeared, an ever-growing accumulation of isolated facts, as impossible for a single intellect to co-ordinate as for a single memory to grasp.

The intricate formula that hang upon these walls, and the boundless variety of phenomena they illustrate, are beginning to be for us as a labyrinth once impassable, but to which we have at length discovered the clue. A sense of mastery and power succeeds in our minds to the sort of weary despair with which we at first contemplated their formidable array. For now, by the aid of a few general principles, we find ourselves able to unravel the complexities of these formulæ, to marshal the compounds which they represent in orderly series; nay, even to multiply their numbers at our will, and in a great measure to forecast their nature ere we have called them into existence. It is the great movement of modern chemistry that we have thus, for an hour, seen passing before us. It is a movement as of light spreading itself over a waste of obscurity, as of law diffusing order throughout a wilderness of confusion, and there is surely in its contemplation something of the pleasure which attends the spectacle of a beautiful daybreak, something of the grandeur belonging to the conception of a world created out of chaos.

PHARMACEUTICAL MEETING.
Wednesday, October 4.

Mr. PETER SQUIRE in the Chair.

THIS, the first meeting of the season, was as usual devoted
to the distribution of the prizes gained by the pupils of
the Society during the past session. The Professors pre-
sented their Reports, and the Chairman distributed the
prizes with a few words of advice and encouragement to
the receivers. The names of the prize-men are as under :
Chemistry and Pharmacy.
Mr. A. R. Hall

Medal.
Certificate of Merit

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F. Oldfield

F. C. Clayton

Botany and Materia Medica.

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G. W. Self (equal)

F. C. Clayton

H. W. Harris

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S. Applegate

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J. A. Thomas

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Practical Chemistry-Laboratory Class.

Pereira Medal

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Prizes for Herbaria.

Silver Medal
Honorary Certificate

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Mr. J. W. White
Isaiah Tansley
Jacob Bell Scholarships.

There was no candidate this year for the Senior, so the Council allotted two Junior Scholarships. These were gained by Mr. A. R. Hall and Mr. S. Applegate.

SOCIETY.

Ordinary Meeting, October 3, 1865.

Nor am I permitted to follow these speculations into another direction. I have to forego, more especially, the MANCHESTER LITERARY AND PHILOSOPHICAL pleasure of submitting to you some of the ingenious explanations which Professor Kekulé, to whom we are greatly indebted for the development of this branch of chemistry, has advanced for the elucidation even of saturated compounds of anomalous constitution. Tempting though the further elaboration of this subject may appear, it would lead me inevitably beyond the legitimate limits of a Friday evening lecture at the Royal Institution.

Indeed, my time, and I fear your patience, are exhausted, and I must add but few concluding words. Your atten

EDWARD SCHUNCK, Ph.D., F.R.S., &c., Vice-President, in the Chair.

A PAPER was read "On the Internal Heat of the Earth as a Source of Motive Power," by Mr. GEORGE GREAVES, M.R.C.S. It has been very generally admitted that coal will not cease to be furnished because of the exhaustion of the stores of the mineral now existing in the coal

NEWS

measures; and further, that the obstacles to the continued
working of the mines will not be engineering difficulties.
The increased depth from which the coal will have to be
brought may add to the cost, but at that increased cost it
will still be for a long time obtainable. The author con-
sidered the real insurmountable obstacle to be the high
temperature of the lower portions of the carboniferous
strata. That temperature had been shown to be at a
depth of 4000 feet at least 120° Fahr., a degree of heat
in which human beings cannot exist for any length of time,
much less use any exertion. It had occurred to the
author to inquire whether the very agency which will pre-
vent the continued supply of fossil fuel might not be
made the means of rendering that supply unnecessary-
whether, in short, the internal heat of the earth might
not to some extent be utilised. One or two modes of
doing this had presented themselves to his mind. One of
these might, he conceived, be the direct production of
steam power by bringing a supply of water from the sur-
face in contact with the heated strata by means of artesian
borings or otherwise.

ACADEMY OF SCIENCES.
October 9.

perhaps, see a recommendation in what the author considers an objection.

Cholera is still the subject of many communications. In one of these M. R. De Wouves says that the premonitory diarrhoea should always be treated with a purgative to procure the expulsion of peccant matter in the intestines. In another M. G. Grimand gives a succinct history of the recent outbreak in Marseilles, which seems to prove conclusively the fact of the importation of the disease from Alexandria.

NOTICES OF BOOKS.

Dublin International Exhibition of Arts and Manufactures: Reports of the Juries, and List of the Awards. Dublin: 1865. THE reporter on Section II. is Mr. Tichborne, who kindly furnished us with notes on this part of the Exhibition; we have consequently but little to add now on the subject. There are, however, some remarks by Dr. Maxwell Simpson, on the articles exhibited by Henner and Co., of St. Gall, Switzerland, which some of our readers may thank us for extracting. The firm exhibited some chemical products which are difficult to find in commerce. These were found to be what may be termed very fair commercial specimens; and Dr. Simpson remarks that "it offers great recog-facilities for original research that such substances can be procured in small quantities and at reasonable prices. Amylene (C,H) was one of the substances examined. Almost the entire quantity taken distilled over between 35° to 45° C. The distillate on being agitated with a solution of chloride of iodine, yielded chloro-iodide of amylene (C,H1CII) a new body, an account of which has not yet been published. The iodide of allyle (C,H,I) is also a good product, the greater part distilled over between 100° to 106 C.; on being agitated with metallic mercury it became a mass of yellow crystals, the mercuro-iodide of allyle [(CH) Hg,I]. The butylic alcohol distilled over between 104 to 120° C., and treated with iodine and phosphorus, yielded iodide of butyle, the boiling-point of which was about 121° C."

M. DE CIZANCOURT presented a memoir "On the Allotropic
Conditions of Iron.' The author, like Berzelius,
nises two allotropic states of this metal, and adopts the
same names for them-ferrosum and ferricum. Ferrosum
is the metal from ores containing protoxide; ferricum is
obtained from the anhydrous peroxide ores. The most
characteristic form of ferrosum is the white crystalline
cast iron (Spiegel Eisen), commonly obtained from the
carbonate, and is best produced at a low temperature.
This form of iron has a strong affinity for carbon. Chemi-
cally it must be classed among the bodies which unite with
one atom of oxygen. Ferricum also combines with carbon
at high temperatures, but deposits it again on cooling.
This form of iron gives the malleable metal, and also
blistered iron. The author states that while ferrosum
easily passes into ferricum, the inverse change cannot be
effected. Ferricum belongs to that class of bodies which
combine at least with three atoms of oxygen and often more,
but always an uneven number of atoms. This memoir
will have considerable interest for metallurgists, and we
shall therefore give it at length.

M. Bultinck presented a note " On the Use of Magnesium
in Voltaic Piles in Place of Zinc." Our readers can
imagine the results. The author shows that a short chain of
twenty elements, each composed of thirty-five millimetres
of thin silver and magnesium wires, wound about pieces of
caoutchouc and properly connected, will produce all the
effects, chemical, physical, and physiological, of a long
Pulvermacher's chain when simply moistened with pure

water.

M. Jennet presented a note "On the Clarification of Peaty Waters by Alum." Most of our readers will have heard of a method of clarifying and rendering portable certain muddy waters by stirring or shaking up with them a very small quantity of finely powdered alum. Then, after standing a few minutes, the suspended impurities deposit, and the water becomes perfectly bright, and at the same time extremely palatable. The explanation of this is as follows:-In dissolving, the alum splits up into sulphate of potash and sulphate of alumina. The former remains in solution in the water; the latter decomposes, and the insoluble alumina unites with and carries down the suspended organic impurities; while the sulphuric acid acts on the alkaline and earthy carbonates, forming sulphates and setting free carbonic acid. The biphosphate of alumina, although slower in its action, the author thinks would be a better clarifier if the carbonic acid set free did not dissolve some of the neutral phosphate. Some persons will,

10

In the Report on Section IV. we find an account of "wood-stuffs" for paper-making, prepared by Roether, of Cassel. The samples were made from four woods, the linden, aspen, pine, and Scotch fir. The best qualities of these, it seems, can be sold for 138. and 16s. the 110 lbs. "The samples of papers," says the Report, "made from mixtures of rags with different proportions of these 'stuffs' are excellent, and show a decided progress in wood paper manufacture since 1862. Among them may be specially mentioned a good writing paper containing 45 per cent. of Scotch fir stuff; an excellent lapping paper containing 65 per cent. ; and a coloured lapping tissue paper which is exceedingly strong, containing 50 per cent. of wood-stuff." These articles and the process by which the stuff is produced, deserve the notice of our manufacturers; but no account of the process is given in the Report.

The Report on Section XXX., Photographs, furnishes us with a very good account of Mr. Swan's casket portraits, an ingenious novelty which deserves notice :

"One of the most curious novelties in the photographic exhibition is the production of what is called casket portraits,' specimens of which are contributed by Mr. Swan, the inventor. For such a really ingenious, original, and scientific contrivance, it seems that the author might have found a more appropriate name, designating more properly the principles upon which it is based, and the manner of its construction. It is, in fact, neither more not less than a real stereoscope, in a different form from that well-known instrument.

"Without being conscious of it the observer has before his eyes, as in the ordinary stereoscope, a picture com.. posed of two different photographs super-posed, each one

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