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The results show that this body has the formula C6H109 and that it is doubtless the third member of the benzole series. Although xylole-first discovered by Cahours in the light oil separated from wood spirit-has had a much lower boiling-point assigned to it, I have retained the name for this body, since the results which I have obtained in the study of the light oil from wood-tar indicate that when the corresponding body from this source is in an equal state of purity its boiling-point will agree with the above determinations. I may here mention that I have obtained a body from wood-tar at about 140°, but nothing between that and 110°, although special pains were taken with the intermediate fractions. That this body boiling at 140° is not identical with cumole from cuminic acid will be made apparent hereafter.

IV. Isocamole (Cymole of Mansfield).- Sp. gr. 0.8643at 0° and 0.853 at 15°. The boiling-point was determined with the usual precautions. Before distillation commenced the temperature of the boiling liquid was 1965; at the close (near dryness), 167°. With the customary corrections for the average, viz., 166'75°, we obtain for the corrected boiling point 169.8°. Analysis.-0*1944 grm. gave by combustion, as before, 06366 of carbonic acid and o'1896 of water.

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Theory Hence it appears that the calculated density on the formula CH12 is 0151 less than that found by experiment. The calculated density on the formula CH1, previously assigned to this body, though without analysis or determination of vapour-density, is 4'645, which is 0302 greater than that found by experiment.

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It will be observed that the difference between the density found and that calculated on the formula C20H14 is not only twice as large as the corresponding density calculated on the formula C1,H12, but that the error is reversed; being with C2H1 a deficiency, while with C8H12 it is an excess. This circumstance goes strongly to show that the lower formula is the true one. I have but rarely met with an instance in which the density found was not greater than the theoretical density; and I have usually observed that the excess of the experimental over the theoretical density is larger in proportion as the boiling-point of the body is highera fact which needs explanation. Wurtz observed a similar difference between the determined and calculated vapour densities of bodies of the formula CnHn and Cn Hn + 2, which he accounted for on the ground that his preparations contained an admixture of bodies less volatile, the vapours of which would remain in the balloon and increase the density. But I do not accept this explanation for the substances here treated of, since they invariably distil without residue within a range of one degree of temperature. I would rather rely on the supposition that the high temperature employed causes In a note the author refers to the publications of Hugo Müller, Béchamp, and Naquet, September, 1864. Müller's results, he says, agree with his own. Béchamp erroneously regards it as a new hydrocarbon, not belonging to the benzole series. Naquet calls it a new hydrocarbon, and gives the formula C18H12.

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partial decomposition of the substance, which would be more liable to occur the higher the boiling point of the body. I do not, however, offer this as an explanation, but merely make the suggestion.

Remarks on Mr. Warren's "Researches on the Volatile Hydrocarbons," by A. H. CHURCH.

IN the CHEMICAL NEWS of December 15, an account of Mr. C. M. Warren's careful experiments on the benzole series is commenced. The way in which some of my early results are criticised compels me to refer at once to

several of his statements.

Mr. Warren cannot confirm all the results of the late Mr. Mansfield, but when this chemist's views are believed to have been incorrect they are spoken of as "an expression of opinion in advance of anticipated results;" but when I am wrong, or supposed to be so, I am severely handled. I am quite ready to admit that my own opinions have in several respects been altered by further researches; while the admirable method of fractionating perfected by Mr. Warren has enabled him to work far more satisfactorily than was possible at the time I tried my experiments on the subject—just eleven years ago.

I regret that Mr. Warren has not made himself acquainted with all my papers and notes on the benzole series. Some of the results which he disputes I have already corrected, others I now interpret differently, while one or two of his own discoveries I have anticipated.

I. Benzole Series.-No chemist disputes the boiling points assigned to benzole, cumole, and cymole—the benzole being obtained from coal naphtha and from benzoic acid, the cumole from cuminic acid, and the cymole from oil of cumin. My own results published in 1855 were not new; they merely confirmed very strongly the results of others :-Benzole, 80-8° C.; Cumole, 148.4° C.; Cymole, 170.7° C. But I unintentionally conveyed the impression that these particular boiling points with those of toluole and xylole had been taken with coal naphtha products in every case. identity of the hydrocarbons from various sources I had accepted too implicitly second hand, but I did not regard it as a new discovery of my own.

The

With regard to toluole and xylole the case is different. The xylole which I obtained with a constant boiling point of 126.2°, I expressly stated in my paper in the Philosophical Magazine for June 1855 to have been derived from wood spirit. This determination does not differ widely from that of Cahours-126°. My reasons for believing a hydrocarbon of the same formula to cxist in coal naphtha are fully given in this latter paper.

My determination of the boiling point of toluole does not differ widely from the results obtained by Glénard and Boudault, and has been since confirmed by Max Dürre. These three determinations are, 103.7°, 1060 and 104°.

II. Parabenzole Series.—I am still convinced of the existence of a series of hydrocarbons in coal. naphtha isomeric but not identical with that to which benzole belongs. The mere non-discovery of parabenzole in any specimen of coal naphtha cannot be taken as proving the non-existence of this body. The differences in boiling point, liquid density, solubility in oil of vitriol, and specific refractive energy between benzole and parabenzole I have already fully described. Wher the abstract of Mr. Warren's memoir is concluded I may recur to this point.

It is curious to notice that Mr. Warren, while disputing most of my results, actually confirms one of the most important of them, though he does this unwittingly. He describes the hydrocarbon boiling at 140° as having the formula, CH, assigned to xylole. This is exactly what I have myself affirmed. The detection, &c., of this hydrocarbon is a discovery to which I lay claim. I have already named this liquid para-xylole and assigned the formula C6H10 to it, and found it to boil between 140° and 141°.

On the Formation of Glucose by Leaves,
by M. BOUSSINGAULT. *

THE supposition that the production of glucose and its
congeners is principally effected by the aerial organs of
plants is contradicted by the abundance of saccharine
matter in the stalks, the roots, and especially by the
formation of the same matter during germination,
when the leaves are not yet formed. But the germina-
tion only transforms starch into glucose, sugar, and
cellulose; it brings no combustible element; on the
contrary, the embryo, for its nourishment, consumes
those pre-existent in the seed.

By looking at the vegetable world in its entirety, one is convinced that the leaf is the first resting place of the glucosides, which, more or less modified, are found scattered in various parts of the organism; that it is the leaf which claborates them, at the expense of the carbonic acid and water. In maize, wheat, &c., the accumu lation of saccharine principles takes place in the stalk, up to the time of flowering, when all that has been formed assists in the formation of the seed. In beetroot this receptacle is the principal fleshy root. But where there is neither stalk nor root, where is the saccharine matter formed by the leaf deposited? In the leaf itself, which is then considerably extended. The most striking example is presented by the American agave, the maquey, the vine of the Mexicans, the culture of which extends from the time of Montezuma and further. The leaves of the agave all grow from the neck of the root; they attain 2 metres in length, 20 centimetres in breadth, and 1 decimetre at the point of attachment. During from fifteen to twenty years these leaves elaborate and accumulate glucose, until the stalk which is to bear the flowers and fruits begins to form. Then the large, coriaceous prickle-edged leaves, after having remained so long inclined to the ground, raise themselves and approach the conical bud, as if to cover and protect it. Then there is a very apparent and gradual movement, seeming to obey a will. The bud lengthens with surprising rapidity, and a flower-stalk, 5 or 6 metres in length, is soon formed. The work of reproducing the seed is thus accomplished, and it is by preventing this that the Indians procure an ample harvest of the sweet sap, by fermenting which they prepare pulqué, their favourite intoxicating drink. One agave plant, in the environs of Cholula, yields in four or five months nearly 1 cubic metre of sweet liquid, after which it dies exhausted, as it would also die exhausted were the stalk allowed to develope and bear flowers and fruit. An agave yields in four months about 100 kilogrammes of glucose, prepared and preserved by its leaves for years.† There is no doubt as to the origin of this glucose; it proceeds from the carbonic acid and water decomposed by the leaves.

* Comptes Rendus, lxi., 664.

+ See Boussingault "Sur le Pulqué:" report made to the Imperial Commission for Mexico.

To conclude, I trust my experiments will enable me to dispute the direct formation of saccharine matter by the green parts of vegetables exposed to the sun.

On the Supposed Nature of Air prior to the Discovery
of Oxygen, by GEORGE F. RODWELL, F.C.S.
(Continued from page 74)

XIV. Rise of Pneumatic Chemistry.-We can
scarcely be surprised that the air received but little
attention till a comparatively late period in the history
of the world, when we remember that there existed no
means of ascertaining even its most salient properties.
Inquiries into the nature of an intangible and invisible
body, which exercises no apparent effect upon the
matter around it, belong to a somewhat advanced stage
of experimental philosophy; they require the assistance
of a large amount of collateral knowledge, of a refine d
manipulation, of a mind tutored in the mode of physical
thought, and used to the classification of diverse phe-
nomena. The most obvious property of matter is its
visibility, and the conception of it divested of that pro-
perty is no small effort to an ordinary mind: we all
know the invariable wonderment produced at a popular
lecture when carbonic acid is poured upon a lighted
taper, or when hydrochloric acid gas and ammoniacal
gas are brought into contact. When we call to mind
the ideas which obtain among the unscientific in the
present day in regard to gaseous bodies, we cannot
wonder that so little was formerly known of the air.

The ancients, although they classed air among the four elements from which they conceived the world had been produced, had no definite idea of its nature. Many philosophers doubted whether it were material, and the great mass of the people scarcely recognised its existence. The fact adduced to prove its materiality (the simplest and most obvious that could occur to the mind) was that it could be felt when in motion—viz., as wind. Anaxagoras went a step further, and urged as an additional proof (a) that a blown bladder resists compression, and (b) that an inverted drinking vessel when plunged beneath the surface of water is found to remain perfectly dry inside, which would not be the case, he argues, unless something material had prevented the ingress of the water. But these crude experiments merely proved that the air is matter.

Then, again, the experiment of burning a candle in a closed vessel standing over water, could throw no light on the nature of the air, as it could not be rightly explained in the then state of science. It may be considered the earliest experiment in pneumatic chemistry; it is mentioned by almost every Middle Age writer on alchemy and chemistry, but scarcely two give a similar explanation of the phenomena observed; nor is this to be wondered at when we remember the amount of chemical knowledge required for its explanation. To explain it in its entirety it was necessary to know (a) that the air is composed of two gases; (b) that they are insoluble in water; (c) that during combustion one of them unites with the burning body; (d) that a gas soluble in water is the result; (e) that the other gas cannot unite with the burning body; and (f) that in a known volume of air there are four volumes of the latter gas to one of the former. No wonder the experiment puzzled the scientific mind for so many centuries. No wonder it became a habit to fasten a pet theory upon it, or to propound one specially for its explanation. Those old philosophers who with difficulty spun out a page or two about it, little thought how much was linked

with the true explanation of the experiment, how their ponderous and unwieldy theories, upon which so much thought had been expended, so little experiment, would have disappeared utterly; how the face of science would be changed when a new race of thinkers, working slowly and laboriously, were destined to elucidate each phase of the experiment.

But although this experiment remained unexplained, it proved to the more observant the important fact that flame requires air for its sustenance-a fact which, although by no means generally admitted, found supporters from the time of Hero of Alexandria. One of the first air-pump experiments tried by Otto Von Guericke was for the purpose of ascertaining whether a candle would continue to burn in an exhausted receiver; and Boyle, in his first pneumatic treatise (1660), mentions several proofs that combustion cannot proceed in a space void of air. In an essay on this subject,* published by Boyle in 1672, we find hydrogen for the first time recognised as an inflammable body. Among other experiments, he poured upon iron filings "a saline spirit, which by an uncommon way of preparation, was made exceeding sharp and piercing;" immediately "fumes" were given off, which proved to be inflammable. When allowed to burn within an air-pump receiver, the flame suddenly enlarged itself on exhausting, and then went out altogether. Boyle does not appear to have studied the properties of the new gas, but contents himself with suggesting that it consists either of "the volatile sulphur of Mars, or of metalline steams participating of a sulphurous nature."

Boyle also published in 1672 an essay entitled "Fire and flame weighed in a balance," in which are detailed a number of experiments made to determine the amount gained by certain metals during calcination. We have previously considered at some length John Rey's important treatise on this subject, published forty-two years earlier. One of the first papers read before the Royal Society (February 23, 1661) was " On the weight of bodies increased in the fire." The experiments were made by Lord Brouncker at the Tower of London, and are given in detail in Sprat's "History of the Royal Society;" but they are by no means concordant-so little so, indeed, that it was not considered as a proved fact that metals gain weight at all during calcination, for we find on March 20, 1661-"The amanuensis was ordered to make the experiment of the calcination of antimony whether it increaseth or not; and to weigh it before and after, in and out of the water."

Boyle found that an ounce of copper filings heated to redness for two hours gained forty-nine grains, while an ounce of tin gained one drachm during calcination. Tin and lead heated in hermetically sealed vessels, underwent partial calcination, from which Boyle inferred that "glass is pervious to the ponderous parts of flame," and that the gain of weight during calcination arises from "extinguished flame" assimilated by the calx. Boyle reduced lead from its calx, hence he considers a calx neither the "caput mortuum " nor the "terra damnata" of the body calcined, as was generally believed, but rather as the body submitted to calcination plus something absorbed during calcination. It is curious that Boyle, who had worked upon the air with certainly more assiduity than any of his contemporaries, should not have attributed the increase of weight of calces to the action of the air upon the body calcined; more especially as in a treatise published in 1674 (" Suspicions about some hidden * "On the Difficulty of Preserving Flame without Air." + CHEMICAL NEWS, vol. x., p. 208.

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qualites of the air") he mentions that marcasite when exposed to the air becomes covered with a body of a vitriolic nature; he also considers that the efflorescence on walls comes from the air, and suggests there is a something of a solar or astral nature, possibly “a volatile nitre," dispersed throughout the air, and necessary for the sustenance of life and flame. As an additional reason for believing that there is some" hidden quality" in the air, he mentions that he made a liquid of "sublimate, copper, and spirit of salt," which was of a dirty red colour so long as it was kept in a closed phial, but when exposed to the air it changed to "a green exceedingly lovely."

I have mentioned above Boyle's supposition that there is "a volatile nitre" in the air, and this leads us to the consideration of that which I conceive forms the basis of pneumatic chemistry-the recognition of a connexion between the air and nitre. We shall find as we proceed the vast importance of the experiments which were made to determine the nature of that connexion. came to be classed together. In the Novum Organum, Bacon urges the necessity of collecting together what he calls "a number of instances agreeing in one form." "Inquisitio formarum," he writes, “sic procedit; super naturam datam primo facienda est comparentia ad intellectum omnium instantiarum notarum, quæ in eadem natura conveniunt, per materias licet dissimillimas." Following out this last clause to the very letter, Bacon takes the heat of the sun as the first "instance agreeing in the form of heat," and classes with it the skins of animals and oil of vitriol, on the ground that the former (as he supposed) contained heat, and the latter burnt linen. On the same principle (and certainly with equal reason) some philosophers traced a relationship between the air and nitre :-nitre, when thrown upon red-hot coals, produces very intense ignition; a blast of air directed upon red-hot coals produces the same effect, the two instances obviously "ineadem natura conveniunt, per materias licet dissimillimas." This mode of procedure may appear crude and likely to mislead, when we consider Bacon's classification of instances agreeing in the form of heat, but it must be remembered that he gives negative instances which qualify the former, and enable the mind to decide whether certain instances which appear at first sight to agree may really be admitted as such. Moreover, the classification is only to be temporarily made, and then to be tested rigidly by experiment. The classification of the air with nitre (as also Newton's familiar classification of the diamond with combustible_bodies), belong to that class of instances called by Bacon "instantiæ conformes sive proportionata," which he defines as " primi et infimi gradus ad unionem naturæ," leading the mind "ad axiomata sublimia et nobilia."§

Let us first understand how such dissimilar bodies

Nitre has always been an important salt; it was known in the East from very early times, and after the invention of gunpowder was largely imported into Europe. Geber, the earliest writer on chemistry (8th century), mentions both nitre and nitric acid, and the former figures prominently in all alchemical and old chemical treatises. It was called saltpetre from the fact of its being found adhering to rocks (TETPOS). Bacon attributes the force of gunpowder to the nitre which it contains, "which having in it a notable, crude, and windy spirit, first by the heat of the fire suddenly dilateth itself, and we know simple air being preternaturally

Nov. Org., Lib. 2, Aph. 11. § Nov. Org., Lib. 2, Aph. 27.

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attenuated by heat will make itself room, and break and blow up that which resisteth it; and secondly, when the nitre hath dilated itself, it bloweth abroad the flame, as an inward bellows."||

Shortly after the establishment of the Royal Society, Mr. Henshaw (one of the first elected Fellows) read a paper before the Society "On the History of Nitre," ¶ in which he says it is probabie "that the air is everywhere full of a volatile kind of nitre" generated in the clouds, inasmuch as he has found it in dew and rain. He was informed, however, that no earth yields so much as that of a churchyard, a fact which militated somewhat against his theory. He speaks of nitre as "the darling of nature, the very basis and generation of nutriment." In a history of nitre written by one William Clark, and published in 1670, we find a section with the rather startling title "A Chemical Analysis of Nitre; " nitre was heated in a retort with potters' earth, when red vapours, smelling like aquafortis, and known as "the flying dragon," were copiously evolved; an analysis, indeed, in the broadest sense of the word, but scarcely justifying the title of the chapter describing it; for we must remember that a hundred years later the term "chemical analysis" could not justly be applied to any operation or series of operations in the chemistry of the period. Clark considers that thunder, lightning, and meteors are caused by nitre in the air; Sennertus attributed thunder and lightning to the meeting of nitrous and sulphurous vapours-an idea evidently originating from the knowledge of the composition and properties of gunpowder. Clark attributes the propulsive force of gunpowder to the sudden conversion of the nitre it contains into air. He mentions the fact that nitre was used by chemists for converting some metals into calx, and he considers that metals become rusted when exposed to the air on account of the nitre which it contains. The latter part of Clark's history of nitre is devoted to the statement of some remarkably wild and useless speculations; in one chapter the author proposes, and endeavours to support the supposition, "That the fiery rain of brimstone and fire on Sodom and Gomorrah was lightning; and that nitre is expressed by the word fire."

Boyle, in a short essay entitled "A fundamental experiment with nitre," mentions that he prepared pure nitre by crystallisation, melted it in a crucible, and threw red hot cinders into the molten mass until deflagration ceased; he then added "spirit of saltpetre" to the residue, and set aside to crystallise; the crystals were found to resemble saltpetre in every respect. He also prepared nitre by mixing "common potashes and aquafortis" and crystallising.

Although a certain relationship between the air and nitre was very generally admitted, philosophers were by no means agreed as to the form and character of that relationship. Some maintained that the effects produced by the air are due to its containing nitre, others that the effects produced by nitre are due to its containing air. Thus, Hobbes and others considered that nitre consists of "many orbs of salt filled with air;" Gassendus, in common with a large number of philosophers, maintained that particles of nitre are diffused throughout the atmosphere; while Hooke, in his ingenious and philosophical theory of combustion,** affirms that the portion of the

"Sylva Sylvarum. A Natural History in Ten Centuries."

Cent. 1, par. 30.

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Read August 14, 1651, and printed in Sprat's "History of the Royal Society."

** See the tenth of these papers, CHEMICAL NEWS for February 17, 1865.

air which renders it the solvent of combustible bodies, "is like, if not the very same, with that which is fixed in saltpetre."

It has always been a matter of regret to us that Hooke's theory of combustion has received so little attention at the hands of the scientific; it was only last year that M. Chevreul (an authority on matters relating to the air), wrote in the Comptes Rendus, "On doit a Stahl la premiere explication de la combustion."++ The theory of Stahl, unsupported either by experiment or sound reasoning, cannot be compared with the theory of Hooke, based upon experimental results, and supported by just and accurate reasoning: Hooke clearly showed the part which air plays in combustion; Stahl adopted the phantasy phlogiston. Then as to priority, Hooke's theory was perfected when Stahl was in his cradle, and was published when he was four years old. Hooke's theory was neglected simply because it was so little known, and this was owing to the manner in which it was given to the world. Not published separately, it was not even designated a new theory of combustion; it forms part of an article on "charcoal or burnt vegetables in the "Micrographia," a work in which we should scarcely look for a new theory of combustion, inasmuch as it professes to detail "some physiological descriptions of minute bodies made with magnifying glasses." Moreover, there is nothing to guide the reader to the subject, and without reading the whole book he would not be likely to meet with it, for it is buried in a mass of irrelevant matter. It is, I conceive, in the causes given above that we must seek for an explanation of the fact that one of the most original and complete theories, which has ever appeared in the history of science, was all but unknown in its own period, and has remained almost unnoticed down to the present day. We have next to consider the important treatise "De sal-nitro et spiritu nitro-aëreo," of John Mayow; the first of the five great works on pneumatic chemistry which were published before the discovery of oxygen.

Chlorine Water.-It has long been known that in chlorine water exposed to air and light hydrochloric acid is formed. Millon has lately shown that some hypochlorous acid is also produced. More recently Barres will has proved the formation of some perchloric acid under the same circumstances, which observation has been confirmed by Schmitt.-L'Institute, 1865, p. 231.

Preparation of Iodide of Potassium. — Fuchs parts of distilled water, and adds thereto 75 parts of pure places 100 parts of iodine in a porcelain dish with 260 carbonate of potash and 30 parts of iron filings. The The action proceeds slowly by itself, but is hastened by mixture is well stirred together, and allowed to stand. the application of heat. When the evolution of carbonic acid has ceased, the mixture is evaporated to dryness with continual stirring. It is better to allow the mixture to stand for some time in a lukewarm drying oven to dryness. The dried mass is then placed in an iron until all the iron is peroxidised, and then evaporate vessel and heated to a dull redness. The residue is then extracted with the smallest quantity of distilled water; the solution, which has usually an alkaline reaction, is then saturated with hydriodic acid, and set aside to crystallise.-Dingler's Polytech. Journal, Bd.

177, S. 251.

"Note historique sur les manieres diverses dont l'air a été envisagé dans ses relations avec la composition des corps." Comptes Rendus for December 12, 1864.

TECHNICAL CHEMISTRY.

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which have lately been made the subject of experiment, with the view to their use in warfare. The author further states that the absorption of ammonia by the gun

Note on the Preparation of Alizarine, by J. WALLACE cotton is accompanied by an increase in weight, not with

YOUNG.

HAVING been lately engaged making some alizarine, and after having tried various methods, I find that on a small scale the following process gives good results, and is readily performed.

Garancine of good quality is extracted with alcohol; the solution is distilled to recover excess of alcohol, and the residuum is carefully dried. A little of the extract so prepared is placed in a small porcelain basin, and over it is inverted a small beaker glass over the mouth of which a piece of filtering-paper has been tied. A very gentle heat is now applied to the basin, the extract soon fuses, and alizarine sublimes, and is condensed on the bibulous paper. The success of the process depends almost entirely on the proper application and regulation of the heat; for, if it be too great, the sublimation is conducted too hastily, and the product will invariably be contaminated or spoiled by an empyreumatic oil which is formed. But if the temperature has been properly regulated the alizarine will be found in magnificent orange red needles, often half an inch in length, adhering to the filtering-paper. If the heat has been very low, the crystals are often found resting immediately on the surface of the extract.

PHOTOGRAPHY.

standing the elimination of a certain amount of oxygen in the form of water. There are, he believes, several stages in the reaction, and he recognises particularly two bodies having the following formulæ :

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Nitro-cellulo-triamide, C12H10O10(NO4)3, (NH2)3. Nitro-cellulo-pentamide, C24H2020 (NO4)5, (NH2) 5.

It is not necessary for the present purpose to follow the author through the remainder of a series of interesting bodies derived from the first of these by the action of lead and potassium salts, or of sulphuretted hydrogen; but we cannot omit to refer to a statement which is embodied in a more recent communication to the French Academy, and is printed in the Comptes Rendus of the 28th August last. M. Blondeau reinarks that he has succeeded in converting the ammoniated gun-cotton (the pentamide already referred to) into a kind of saline combination by treatment with hydrochloric acid; and, furthermore, that the same product may be obtained by boiling, for half an hour, gun-cotton in a tolerably strong solution of sal ammoniac, then washing in a plentiful supply of water, and drying in the sun. the compound thus formed is stated to be

The formula of

C24H20O0(NO)5, (NH2)5.(HCl) s.

The substance is said to be permanent, and to resist decomposition at all temperatures not exceeding that of boiling water; it is equally explosive with, but gives off during combustion, certain products in addition to those furnished by ordinary gun-cotton, particularly

Observations on Some New Compounds of Pyroxyline cyanogen and the vapours of chloride of ammonia.

by JOHN SPILLER, F.C.S.

Conceiving this substance to be well fitted for the production of a collodion which, by the addition of nitrate IN the Comptes Rendus of the Academy of Sciences, of silver, would become at once available for the collodiounder date May 30, 1864, appeared an interesting com- chloride process, I attempted its preparation in the hope munication from M. Blondeau, which was devoted to the that it might prove to be soluble in ether and alcohol. description of some new ammoniated products of pyroxy-Failing, however, in the first attempt, I made repeated line upon the examination of which, at about the same experiments upon several different varieties of gun-cotton time, I happened also to be engaged in connexion with (the exact quality of which the author omitted to spethe investigation of gun-cotton, undertaken by Mr. Abel.cify), following to the letter the instructions given, but The substances in question are formed whenever gun- without being able in any instance to fix an appreciable cotton, or the soluble variety of pyroxyline, is exposed to quantity either of chlorine, or of the elements of amithe vapour of ammonia, and the chemical action facili-dogen. It is needless to observe that a mode of formatated by maintaining a slightly elevated degree of tem- tion founded upon the successive production of the amperature. The operation is best performed on a small moniated and of the chlorinated compounds would be too scale, by treating some forty or fifty grains of explosive tedious to permit its use in the practical direction already cotton in a long-necked flask with aqueous ammonia indicated. (sp. gr. 880), added by successive portions of eight or ten drops, and the flask fitted with a very loose cork, immersed for an hour or two in a water bath kept at the temperature of 100° to 120° Fahr. The colour of the gun-cotton speedily changes to a light yellow, which gradually darkens to a russet brown, and its physical aspect undergoes a modification, to the extent of becoming a soft, friable mass, which still presents a fibrous appearance. By this treatment the explosive properties remain almost, if not quite, unimpaired; and it is worthy of mention that the production of this substance in large quantities is attended with risk, and that explosions have occurred in the course of my experiments whenever I increased the amount of material operated upon, or endeavoured to employ a somewhat higher temperature, in order to expedite the reaction.

M. Blondeau claims for his compound advantages on the score of greater permanence and superior explosive power, when compared with the varieties of gun-cotton

Inasmuch as I could not perceive any alteration in the properties of the gun-cotton which had been boiled with solution of sal ammoniac, and failing in obtaining analytical proof of the existence of chlorine and amidogen, I proceeded next to compare the weight of the substances before and after treatment. In operating upon weighed portions of the highly-explosive tri-nitro-cellulose, and likewise of the inferior nitro-compound usually employed in the manufacture of collodion, I could not discover the slightest increase, nor indeed any alteration, in weight as the result of such treatment. The samples were, of course, thoroughly washed in many changes of distilled water (until nitrate of silver failed to show any indication of alkaline chloride yet remaining) and they were allowed to dry by free exposure to air. According to M. Blondeau's formula, which exhibit a constitution embracing a greater number of hydrogen and oxygen atoms than usually assigned by English chemists, the chlorinated product should weigh at least one-third more than

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