PHOTOGENIC GAS.

A COMPANY has recently been formed for the purpose of introducing M. Mongruel's invention into general use. According to the specification of his patent, this consists in a particular form of apparatus applicable to the saturation of ordinary gas or atmospheric air, with the vapour of a volatile hydrocarbon, so as in the one case to increase the illuminating power, and, in the other, to produce an illuminating gas.

The carburation of gas by such means is no novelty, inasmuch as it was one of the earliest improvements of gas-making suggested by Mr. George Lowe so far back as 1832.

The production of an illuminating gas by saturating atmospheric air with a volatile hydrocarbon vapour is also no novelty, since it is one of the means by which Mr. Mansfield proposed to use the more volatile liquids, obtainable from coal tar, for producing light.

When M. Mongruel's project was first made known in this country, however, the accounts given of it were calculated to lead to the belief that it was an entirely new invention. A certain amount of mystery was thrown around the liquid employed, which was not without its effect in bringing many people to believe that the invention was in that. But to any one at all acquainted with the subject it was evident that there could not be any great secret in this liquid, and that invention was out of the question with regard to it. There was no doubt that the liquid used was a hydrocarbon of sufficient volatility to be diffused through the air in such amount as to render it capable of burning with a luminous flame. Moreover, an abundant source of such a liquid had just before been discovered in the American petroleum, and precisely this very volatile portion was then still without any useful application. There is no longer any doubt about the nature of M. Mongruel's invention. It is simply a particular apparatus devised for the purpose of bringing air or gas into contact with the liquid hydrocarbon to be volatilised; in fact, a special means of carrying into effect the suggestions of Mr. Lowe and

Mr. Mansfield.

The advantage claimed for this apparatus of not impoverishing the liquid diffused into the gas or air, will obviously depend solely upon the nature of the liquid itself. If the liquid employed is not uniformly volatile, but if, like the coal tar naphtha used by Mr. Lowe, it consists of a mixture of unequally volatile liquids, the result in M. Mongruel's apparatus will be the same as in Mr. Lowe's, viz., that only a portion of the liquid the more volatile portion-will be volatilised, and the remainder will be, as M. Mongruel expresses it, "im

*CHEMICAL NEWS, February 21, 1863.

poverished." or in plain English it will be incapable of being volatilised into the air or gas, and of being retained by them during their passage through the pipes to the place where the light is to be produced. This was just the result obtained in naphthalising gas by Mr. Lowe's method; and, in the case of Mr. Mansfield's plan of using benzol, the difficulty was in preventing the hydrocarbon from becoming solid, in consequence of the cooling effect of its evaporation.

Hence it is absolutely necessary to have for this purpose an extremely volatile liquid, and one which is at the same time of uniform volatility, not a mixture of liquids differing in volatility. No statement is made as to the cost at which a liquid so suited for the purpose can be obtained, though there are reasons for the opinion that the volatile oil of the American petroleum will maintain a high price.

It is stated that 1000 cubic feet of gas require nearly a gallon and a-half of the liquid, so that it may be expected that the cost of the gas will be doubled. At the same time it is stated that the illuminating power is increased fourfold.

One of the advantages claimed for this apparatus is the purification of the gas carburated, but it is not stated how the purification is effected, nor does there appear to be any possibility of the gas being in any way purified by this treatment.

the illuminating power of the gas, is quite silent with Altogether the prospectus, though loud in praise of regard to many important particulars on which the success of this project depends in a far greater and more essential degree than it does upon the use of M. Mongruel's generator, however ingenious that may be in its construction, and however efficient for saturating gas or air with a liquid of sufficient volatility. In one of the testimonials attached to the prospectus, incidental reference is made to a carburating liquid so volatile that it vapourised at a temperature one degree above the freezing point, and there is much reason to think that if such a liquid be requisite this plan of obtaining light would be very costly. Among other particulars of this have been given as to the degree of volatility necessary kind, it might have been expected that some data would for the liquid used, the cost of it, the cost of the apparatus, and the degree of security or provision against risk of explosion by the production of an explosive mixture of air and hydrocarbon vapour. These are all most important points, of which no mention is made. absence of any satisfactory statements as to these points, It is not, therefore, to be wondered at that, in the on which the success of the company's enterprise is so greatly dependent, no little surprise is felt at the very large sum of 50,000l. proposed to be paid to the inventor of the mere apparatus for effecting a result which, if desirable, might be easily obtained by many other means far less costly, and probably not at all less efficient.

SCIENTIFIC AND ANALYTICAL

CHEMISTRY.

An Alleged New Metal.

MR. SONSTADT, who has recently obtained a patent for the manufacture of magnesium, considers that the black residue mentioned by MM. Deville and Caron, as being left when impure magnesium is distilled, contains a new metal. He describes the following process for obtaining it :

An intimate mixture of calcined magnesia with oneeighth its weight of amorphous phosphorus, is ignited in a covered porcelain crucible until phosphorus vapour is no longer given off. The grey residue is extracted by hydrochloric acid, and the undissolved portion repeatedly boiled with hydrochloric acid. What then remains is nearly black; it is ignited with dry hydrate of soda, the mass digested in water, and the yellowish insoluble portion, well washed by decantation. This yellow substance, dissolved in acid, gives the following reactions, said to be characteristic of the new metal. The solution gives a blood-red colour with alkaline sulphocyanide, a blue precipitate with ferrocyanide solution, and, after treatment with reducing agents, a blue precipitate with ferrocyanide solution. But, unlike true Prussian blue, the colour of these precipitates is not changed by ammonia, unless they are contaminated with iron.

The oxide, precipitated by an alkali, is said to require much more intense heat for its reduction than iron oxide, and the dark spongy mass obtained, is not magnetic. Mr. Sonstadt has not found any reagent capable of separating the new metal from iron, nor yet any reagent capable of entirely separating it from a magnesian solution, although every trace of iron may be precipitated.

Anomalous Vapour Densities.

M. CAHOURS has long since shown that the vapours of some liquids do not present the characters of permanent gases, except at temperatures much above the respective boiling points. In determining the density of such a vapour at temperatures rising from near the boiling point of the liquid to a temperature at which the density presents no further change, it is easy to perceive that, until that limit is reached, the vapour is not in a definite condition, but the densities at different temperatures, represented graphically, correspond to a curve gradually approximating to the axis of the abscissæ, finally becoming parallel with it, and remaining so until the degree of temperature is reached at which there is a disassociation of the constituents of the molecules.

This anomaly, presented by many different substances, seems to be independent of the nature of the vessel containing the vapour. It may be that, at temperatures near the boiling point of a liquid, a portion of the liquid remains dissolved in the vapour, giving rise to the excessive density, and that, as the proportion of liquid so dissolved decreases with elevation of temperature, it ultimately disappears, and then the vapour conforms to the law obtaining for permanent gases.

It is of interest to inquire what is the effect produced by introducing into the molecule of a substance which gives vapcur of anomalous density, other constituents in the place of its normal constituents. For example, acetic acid affords a remarkable instance of anomalous

Register of Facts Relating to Literature, Science, and the Arts, June, 1863, p. 458.

vapour density. Representing it according to Gerhardt, by the formula

M. Cahours' ex

substitution may be effected in the molecule either of the hydrogen in the acetyl, or of the hydrogen or oxygen combined with the radical. periments have led him to the conclusion that when the hydrogen combined with the radical, is replaced by substances capable of giving rise to volatile derivatives, there are no longer such anomalies in the vapour densities as exist in the vapour density of acetic acid. Thus methyl, ethyl, and amyl acetates, and even acetic anhydride, which differs from the normal acid only in containing a second equivalent of acetyl, in place of the hydrogen united with the radical of the normal acid, all give vapours which conform to the law, and present the characters of permanent gases at temperatures very near their respective boiling points.

This is shown clearly by the following table :—

substance having analogous chemical functions, such as methyl, ethyl, &c.

Gay-Lussac's researches on gaseous combination have shown that when two gases combine in equal volumes, the compound gives a gas equal in volume to the joint volume of the constituent gases, while there is always a contraction, greater or less, when the gases combine in unequal volumes. There are but two exceptions to this rule,-chloro-carbonic and chloro-sulphuric acids.

Equal volumes of hydrochloric acid gas and of ammonia combine, and produce a neutral substance whose vapour volume is, according to Mitscherlich and Deville, exactly equal to that of the sum of the volumes of its constituents, that is to say, eight volumes.

The opinion held by Cannizzaro, Kopp, Pebal, Wanklyn, and Robinson, that this difference is due to the disassociation of the constituents of the salt, does not appear to be maintainable since the results obtained by M. Deville, showing that sal ammoniac has more stability than one of its constituents. This is not an isolated fact; the molecule of phosphorus perchloride also corresponds with eight volumes of vapour, and hence M. Cahours has regarded it as consisting of equal volumes of protochloride and of chlorine.

Hydrochloric acid also combines with oil of turpentine, amylene, caproylene, or caprylene in equal volumes producing neutral substances, and it might have been expected that they would correspond with eight volumes of vapour. But this is not the case, and experience has shown that, like most volatile organic substances, their molecules correspond with four volumes of vapour, as will be seen by the following table :

M. Cahours considers that this difference arises from the circumstance that in the combination of ammonia and

hydrochloric acid both maintain their normal volumes, the saturation of their constituents being complete, while, on the contrary, the carbon in the hydrocarbons is not saturated fully, and hence there is a tendency to the production of substances represented by the formula C2H2mX21

X2 representing an elementary substance such as H2Cl2 Br2Cy2, or their equivalents HCl, HBr.

In these compounds the chlorine or bromine no longer exists in the state of hydrochloric or hydrobromic acids combined with a substance which neutralises them, nor in the state of chlorine or bromine combined with a radical analogous to metals; but they exist, in some sort, in a latent condition, as is shown by the inactivity of these substances in regard to an alcoholic solution of silver nitrate as compared with the reaction between sal ammoniac and that salt.

The terms hydrochlorate, &c., applied to those compounds appear therefore to be improper, and it would be more consistent to regard them as isomeric with chlorhydramylic ether, &c., and differing from these substances only in a greater tendency to split into the hydracids and hydrocarbons from which they were produced.

Acetic acid combines with ammonia in equal volumes, producing a neutral substance, but M. Calours has not obtained results indicating its vapour density to correspond with eight volumes, as in the case of sal am

moniac. This is not in consequence of the decomposition of the salt into binacetate, for by heating acetate of ammonia to 200° in a flask, the vapours given off were sometimes alkaline and sometimes acid, but the crystalline residue in the flask was neither acid nor alkaline. It disengaged ammonia abundantly when heated with potash, boiled regularly without alteration at 218° to 220°, and presented all the characters of acetamide. The vapour density was 2.10; calculated, 2'06. Ammoniacal salts of oxyacids give the same results, so that there is no possibility of ascertaining the density of their vapours experimentally, or if their molecules are similar to those of the hydracid compounds of ammonia.

New Methods for Testing the Purity of Alcohols and Ethers, by M. BERTHELOT.

THOUGH alcohols and ethers have been carefully purified by distillation and desiccation, there has hitherto been in most cases no means of controlling their purity. The following are the results of my researches:

1. I take as a starting point the fact that a compound ether, if pure, is decomposable by an alkali, by saturating an equivalent weight of this alkali. By this means, as I showed about ten years ago, the analysis of ethers and analogous compounds, is founded on an alcalimetric test, based on the use of a standard solution of baryta.

2. By means of the same liquid the smallest quantities of compound ethers may be recognised and estimated in alcohol or in simple ethers, provided these bodies are not alterable by alkalies. 10 cubic centimetres of a standard solution of baryta, and a known weight of the body to be tested, are inclosed in a flask. It is then heated for about an hundred hours at 100°; if the alcohol is pure, as is oftenest the case with ordinary alcohol, the standard of the baryta does not change. Amylic alcohol, on the contrary, almost always contains a small quantity of compound ethers, as also does ordinary ether, even after digestion on milk of lime.

Glycol prepared by the ordinary methods, and rectified to a certain point, is particularly impure. I have found in it as much as 22 per cent. of combined acetic acid, corresponding to 40 per cent. of monoacetic glycol. This fact may occasion more than one error, and the knowledge of it will be useful to chemists occupied with

this curious substance.

To recognise the presence, without estimating, of a neutral ether in an alcohol, I heat the alcohol with twice its volume of water, for twenty hours at 150°. Most of the neutral ether changes into acid.

3. The presence of a free acid in an alcohol or an ether is so easily recognised that I need not stop to describe the process. Formic ethers, for instance, are always acid; but they decompose so promptly as to prevent the exact estimation of the free acid. The free acid of other ethers, on the contrary, can be precisely estimated.

4. The presence of a small quantity of water in a neutral ether may be detected by heating this ether to 150° during twenty or thirty hours; the water decomposes an almost equivalent quantity of ether into acid and alcohol. The acid is then estimated by a standard solution of baryta. On submitting acetic ether, carefully purified by the ordinary methods to this test, it will obstinately retain a centième of water, which is with great difficulty eliminated.

5. The presence of a small quantity of water in alcohol may also be detected by mixing the alcohol with

280

CHEMICAL NEWS, June 18, 1863.

not become acid.

6. The presence of a small quantity of alcohol in a neutral and anhydrous ether, acetic ether for instance, may be detected by heating the ether with a known weight of quite pure acetic acid. The standard of the acid will diminish according to the amount of alcohol.Comptes-Rendus, lvi., No. 18.

TECHNICAL CHEMISTRY.

Animals.

MM. DUMAS and Boussingault have represented the general features of the balance existing between the phenomena of animal and vegetal life, but many questions of detail still remain to be determined, and one of the most important is that relating to the restoration of nitrogen to the atmosphere by animals, its passage from the atmosphere to plants, and thence again to animals. The experiments of MM. Edwards, Dulong, Despretz, Regrault, and Reiset have shown that animals eliminate nitrogen. The amount of nitrogen thus liberated is not more than about 1 per cent. of the carbonic acid expired, and it varies according to the feeding and condition of

the animals.

In agriculture it has been considered that all the nitrogen of the food of animals, over and above that assimilated by them, is restored to the land in the form of manure. But this is not the case.

When the study of this subject was undertaken, in 1847, by M., Barral, only two experiments had been made with regard to it by M. Boussingault. He found that during twenty-four hours a horse eliminated twentyfour grammes of nitrogen, and a milch cow twentyseven grammes; in the one case 17 per cent., and in the other 13 per cent. of the nitrogen in the food.

M. Barral has since found that, in the twenty-four hours, an adult man eliminates from nine to fourteen grammes of nitrogen, an adult woman about twelve grammes, and a child five years old three grammes, corresponding to more than a third of the nitrogen in the food. A sheep in the same time eliminates about six grammes, one-third or one-fourth the nitrogen in the food. Very nearly the same results have recently been obtained by M. Reiset with fattening cattle.

The general result of the observations was, that in the twenty-four hours, forty-eight grammes of nitrogen were required in the food for each 100 kilogrammes of live weight, and that one-fourth of this was eliminated and returned to the atmosphere as nitrogen. In a year, the same live weight would eliminate 4380 grammes of nitrogen. In other words, a consumption of food equivalent to 6000 kilogrammes of hay involves a loss of 1500 kilogr.

This result confirms M. Boussingault's opinion that farm animals are not, as is supposed, producers of manure, but rather consumers of manure; they convert fodder into materials rapidly assimilable by plants, only at the cost of a considerable loss. It appears from this that the practice of green manuring is advantageous when it is not necessary to obtain manures more rapidly assimilable, or when the feeding of cattle is not remunerative. It also follows that the fertility of a farm sup*Comptes-Rendus, lvi., 765.

There appears to be no evidence of the direct All the experiments that have been made on this subject have observations show that plants obtain a part of their given negative results. Still, M. Boussingault's nitrogen from some source other than the soil or the manure supplied to them. They obtain that nitrogen indirectly from the atmosphere. With the view of elucidating this subject, M. Barral, in 1851, commenced observations of the rain-water falling in the neighbourhood of Paris. He found nitrate of ammonia to be constant in the atmosphere, and that rain-water always contains sensible quantities of nitric acid and ammonia. But the quantity was insufficient to account altogether for the elimination of nitrogen by animals, though it was sufficient partly to account for the production of crops from unmanured land under the bare fallow system.

M. Barral considers that the oxidation of nitrogen in the soil may be the source whence plants derive great from the atmosphere the nitrogen supplied to it by part of their supplementary nitrogen, and of withdrawing animals. He has found that water discharged from drains contains nitrates in amount proportionate to the fertility of the land it comes from.

is determined in soils by vegetation itself. By growing He does not agree with the opinion that nitrification plants, in confined atmospheres of oxygen and carbonic acid, without any nitrogen, he always found some nitrogen eliminated, but that might originate from the decomposition of organic substances.

The Function of Atmospheric Oxygen in the Destruction of Animal and Vegetal Substances after Death, by M. PASTEUR.*

THE most ordinary observation has at all times demonstrated that animal and vegetal substances, exposed after death to contact with atmospheric air, or buried in the earth, disappear, in consequence of various transformations.

Fermentation, putrefaction, and slow combustion, are the three phenomena which concur in the accomplishment of this great fact of the destruction of organic substances a condition necessary for the maintenance of life on the earth.

Dead substances that ferment or putrefy do not yield solely to forces of a purely physical or chemical nature. It will be necessary to banish from science the whole of that collection of preconceived opinions which consist in assuming that a certain class of organic substances-the nitrogenous plastic substances may acquire, by the hypothetical influence of direct oxidation, an occult power, characterised by an internal agitation, communi*Comptes-Rendus, lvi., 734,

cable to organic substances supposed to have little stability.

In M. Pasteur's memoirs, and more especially in a recent communication, he has pointed out precisely. what are, in his opinion, the true causes of fermentation, and has stated the principal result of his researches on putrefaction, properly so-called.

In every case, life, manifesting itself in the lowest forms of organization, appears to be one of the essential conditions of these phenomena, but life of a nature unknown hitherto; that is to say, without consumption of air or of free oxygen.

He now endeavours to demonstrate experimentally that the slow combustion which takes place in dead organic substances, when they are exposed to the air has, in most cases, an equally intimate connection with the presence of the lowest forms of life. This leads to the general conclusion that life takes part in the work of death in all its phases, and that the three terms of that perpetual return to the atmosphere, and to the mineral kingdom, of the elements which vegetals and animals have abstracted from them, are correlative acts of development and of the multiplication of organised beings.

In May, 1860, an exhausted flask, of 250 cubic centimetres capacity, containing 80 cubic centimetres of sugar solution with yeast, which had been heated to ebullition, was filled with air. Immediately after admitting the air, the point of the flask was again sealed by the blowpipe.

Under these circumstances, it often happens that the liquid in the flask does not give rise to the production of infusoria or micoderms, and that it remains limpid after the admission of air to the flask. This was the case in the above-mentioned experiment. The liquid was still unaltered in appearance on February 5, 1863, and at that time the air in the flask was found to consist ofOxygen

Carbonic acid

Nitrogen by difference

18.1

This shows that, during the lapse of three years, the albuminous substances of the yeast water, associated with sugar, and exposed to ordinary atmospheric air under conditions in which animalcules or micoderms were not developed, had absorbed 27 per cent. of oxygen, which they had partially converted into carbonic acid. This direct oxidation or slow combustion was very slight, although the flask had been kept for eighteen months at a temperature of 25° to 30° C.

On March 22, 1860, a flask of 250 cubic centimetres capacity, and containing 60 to 80 cubic centimetres of boiled urine, was filled with air deprived of organised germs by heating it. The liquid was still quite limpid in January, 1863. Its colour had become slightly darker. A crystalline sandy deposit of uric acid had separated in small quantity on the sides of the flask. There were also a few bunches of acicular crystals of lime phosphate. The urine was still acid, but not quite so much so as at first. It smelt exactly the same as fresh boiled urine. The air in the flask consisted of

11'4

On June 17, 1860, a flask of 250 cubic centimetres capacity, containing 60 cubic centimetres of milk, boiled two or three minutes, was filled with air that had been exposed to a red heat. On February 8, 1863, the milk was almost neutral to test paper, with a tendency to alkalinity. It had the ordinary taste of milk, with a slight flavour of suet. By standing, the fatty substance separated in clots, and by shaking the appearance of fresh milk was again presented; it was not at all curdled. The air in the flask consisted of

The fatty substance of the milk had absorbed a large proportion of the oxygen, as in De Saussure's experiments with oil. But still, after three years, there remained some free oxygen, although the direct oxidation of fatty substances is considered to take place very readily. By repeating these experiments under the same conditions, but under the influence of the development of organised germs of the lowest forms of animal and vegetal life, all the oxygen of the air in the flasks was absorbed within the space of a few days, with simultaneous disengagement of carbonic acid in varying proportions.

On February 26 last, a flask containing 10 grammes of oak sawdust, and some water that had been boiled with it, was filled with air that had been exposed to a red heat. A month afterwards the air in the flask consisted of

Oxygen

Carbonic acid

Nitrogen by difference

16.2

In a similar experiment, made without any precaution for excluding organised germs, the air of a flask containing four litres was found, after fourteen days, to contain 72 per cent. of carbonic acid, and 300 cubic centimetres of oxygen had been consumed, while in the former experiment only a few cubic centimetres were consumed. This ready combustion of sawdust when exposed to atmospheric air was long since observed by De Saussure in his researches on the formation of soils.

Whence arises this great difference between the results of the two experiments? At first sight there appears to be no clue to it. But if the surface of the sawdust is examined by the microscope, it is found, in the case where no precaution was taken to exclude organised germs, to be covered with a scarcely perceptible film of sporules and mycelium of various micoderms.

In examining the slow combustion of dead organic substances under the influence of atmospheric oxygen alone, it will be found that it varies in degree and in mode of action, according to the nature of the substances, almost as the oxidation of metals differs.

Carbonic acid

11'5

Nitrogen by difference

77'1

The constituents of living organisms might be regarded