142 Chemical Notices from Foreign Sources. alloys by means of electro-deposition, have been extended. A small room has been set aside for chemicooptical work, and fitted with a large reflecting goniometer, a Landolt's optical circle, a Browning's spectrometer, a large direct vision spectroscope by Zeiss, a large inverted microscope, a smaller microscope, and three dissecting microscopes by Zeiss and Toller, and a saccharimeter by Soleil. It may be interesting to the heads of colleges and scientific institutions in this country to note the list of desiderata which Prof. Wing still considers needful before the chemical department of the Institute can be pronounced satisfactorily provided for: CHEMICAL NEWS, in water. I consider this as an interesting discovery, and one that may enable us to explain the persistent suspension of clay in what we take as pure water. For instance, the purest water we would take for experiments of this sort contains ammonia, either free or as carbonates. Why not, therefore, suppose that this ammonia forms a compound with the silica of the suspended clay, resembling soap in type of constitution, silica of course corresponding with the fatty portion of such substances. As is well known, all soaps deport themselves like clay with regard to the phenomena under consideration. I would like to know the deportment of pure water with pure hydrous silicate of alumina in regard to the question under consideration. Clay seems permanently suspended in strong ammonia.—I am, &c., WILLIAM SKEY. "The instruction in chemistry is much hampered by the want of a laboratory for qualitative analysis apart from the laboratory used for instruction in general chemistry; of a laboratory for organic chemistry; of a laboratory for applied chemistry; of a suitable reading room where the books of the chemical library may be consulted and writing done; of a number of small rooms for the use of CHEMICAL NOTICES special apparatus." We regret to learn from a foot-note that the balanceroom with its contents and the collection of substances for analysis have been destroyed by fire, and the library very much damaged. We have no doubt that many chemists in this country who have on hand substances of known composition would be happy to assist in restoring the lost collection if some channel were pointed out. Amongst the theses presented by graduates, we find only one which can be pronounced strictly chemical, i.e., a paper on "Anthracen Pressings," by L. P. Kinnicutt. The subject is highly interesting, but the abstract given is so exceedingly brief that no opinion can be formed as to the merits of the essay. It must be remembered that in addition to the chemical department, or as we would rather say, faculty, chemistry forms a feature more or less prominent in the courses of mining, engineering, metallurgy, physics, natural history, and general science. Five professors and as many assistants are occupied with various phases of our science. As a novelty we may point out the introduction of "military science and tactics as a regular feature in all the departments. Were any of our English colleges or scientific institutions to take a similar step it would be incontinently stormed, sacked, and burnt to the ground by our advanced humanitarians, who protest even against the introduction of military drill into elementary schools. FROM FOREIGN SOURCES. NOTE.-All degrees of temperature are Centigrade, unless otherwise expressed. Comptes Rendus Hebdomadaires des Seances, de l'Academi Alcoholic and Acetic Fermentation of the Fruits, Flowers, and Leaves of certain Plants.-S. de Luca.— In close vessels fruits keep for a greater or less length of time, whether in hydrogen or carbonic acid, or in a vacuum, or in a limited quantity of air. In such conditions fruits undergo a slow fermentation, with development of carbonic acid, nitrogen, and, in some cases, hydrogen, and with formation of alcohol and acetic acid these phenomena are produced imperfectly on account of without the intervention of any ferment. In closed vessels the strong pressure produced by the gases evolved. Leaves and flowers behave like fruits in a limited atmosphere, either of carbonic acid, hydrogen, or air, in a vacuum or in sealed vessels. Moniteur Scientifique, du Dr. Quesneville, Salicylic Acid in the Milk Trade.-Drs. L. Manetti and G. Muso.-The authors recommend the use of salicylic acid for the preservation of cream in small farms where butter is made only a few times in the week, and for the preservation of butter where there is no convenience for storing it in places at a temperature not higher than 6° to 8° C., as well as to keep it from rancidity when forwarded during the summer season to distant markets. Researches on Viscous Fermentation.-A. Commaille. Not suitable for abstraction., Study on Coffee.-A. Commaille.-The author has endeavoured to ascertain if it is possible to class coffees by analysis, as the brokers, merchants, and experts do by certain outward characteristics or by taste. In this attempt he does not consider that he has been successful. History of the Manufacture of Turkey-Reds.Theodore Chateau.-A continuation; unsuitable for abstraction. Constitution of the Derivatives of Benzin.—M. E. Nolting.-A lengthy treatise, containing a large amount CHEMICAL NEWS, Chemical Notices from Foreign Sources. of hypothetical matter, somewhat naïvely ushered in with the confession that "not merely the practical man, but even the theoretical chemist, has difficulty in finding his way across the labyrinth of memoirs and dissertations, and in extricating himself from the chaos of contradictory hypotheses!" New Class of Colouring Matters.-M. Ch. Lauth.The raw materials employed for obtaining these new products are the aromatic diamines obtained on reducing the nitro-derivative from the acetylisation of organic bases. Thus, taking aniline for an instance, acetanilide is first prepared, then nitracetanilide and nitraniline; then the nitraniline is reduced either by iron and acetic acid, or by tin and hydrochloric acid. In the first case it is necessary, when the reaction is completed, to add to the mixture an excess of lime and to distil, obtaining thus B-phenylendiamine, which a single rectification yields perfectly pure; in the second case we obtain a liquid, from which the tin is removed by zinc, and this mixture may serve at once for the production of the colouring matter, as will be at once explained. The various isomeric diamines have been studied for a long time with the object of turning them to account in the production of colouring matters: the aniline-brown obtained by the action of nitrous acid upon a-phenylen-diamine is the only interesting product hitherto obtained. We arrive at different results if we begin by introducing into the B-phenylen-diamine a new element, sulphur. This B-phenylen-diamine may be obtained by heating the diamine with its own weight of sulphur to 150° to 180°, when an abundant escape of sulphuretted hydrogen occurs. When the reaction is at an end, the mass is treated with hot dilute hydrochloric acid, and filtered to remove excess of sulphur. The liquid thus obtained gives splendid violet-blue colours with oxidising agents. It is, perhaps, more advantageous, and certainly more expeditious, to produce the sulphuration and oxidation in a single operation. For this purpose the hydrochloric solution of the phenylen-diamine is saturated with sulphuretted hydrogen (and we may, in this case, utilise directly the liquid containing zinc mentioned above), and we add perchloride of iron; the sulphur liberated combines in the nascent state with the base, and if the addition of the oxidiser is continued little by little the colouring matter is developed and precipitated. It is filtered, washed with slightly saline water to eliminate certain impurities, dissolved in boiling water, and let cool, when it is obtained pure in splendid crystals. The following are the proportions employed:-To 20 grms. of hydrochlorate of phenylen-diamine-Water saturated with sulphuretted hydrogen, 4000 c.c.; hydrochloric acid, 20 grms.; perchloride of iron in solution at one-tenth, The new violet is a beautiful dye, giving very pure shades, much more blue than can be obtained with Paris violet of the bluest quality, and it preserves its special tone by artificial light. It is very soluble in boiling water, but the smallest trace of foreign matter modifies its solubility. The alcoholic solution is redder than that in water, and is dichroic. The solution in alcoholic soda is of a splendid magenta-red. Soda added to the solution of the violet gives a brown precipitate, the base of the new colouring matter; ammonia and acids give a violet precipitate, soluble in an excess of acid. The acetic solution is-violet; that in mineral acids a fine pure blue; on dilution with water it is re-precipitated. Metallic salts give precipitates which re-dissolve when the salt has been eliminated by washing; chloride of zinc gives a very bulky amaranth-red precipitate; chloride of sodium separates the violet from its solutions, but converts it partially into a new violet substance insoluble in water. If this precipitation is several times repeated the transformation is complete, and the soluble colouring matter disappears entirely. Boiling with salt water gives rise to the same reaction. Tannin forms with the violet a compound insoluble in water. Reducing agents completely decolourise the solutions of this dye, but the colour returns on exposure to the air. Oxidising agents also 500 c.c. 143 destroy it rapidly. The new colour, like most of its congeners, is capable of yielding other colouring matters by substitution; if heated with aniline it yields a blue soluble in alcohol, but insoluble in water; if submitted to the action of aldehyd, iodide of methyl, &c., under ordinary conditions it is transformed into blues of a more and more green tone, but of great purity, and which present the renarkable feature that they are soluble in water, and may be fixed in dyeing by merely immersing the fibre. The colouring matter just described has been obtained with B-phenylen-diamine; if we set out from pseudo-toluydin we obtain a violet much redder, and crystalline toluydin yields a violet-red. It is very probable that in the same circumstances other organic bases will likewise produce colouring matters. Sulphur, then, may play a part in the formation of colouring matters, and as it is permissible to suppose that other simple bodies possess analogous properties, the field of research is indefinitely extended. Ferments and Fermentations.-M. Charles Blondeau.-Unsuitable for abstraction. Les Mondes, Revue Hebdomadaire des Sciences, Soap obtained directly from Salt.-If tallow, òil, and resin, the matters commonly employed in soap-making, are heated with an excess of common salt, ammonia, and water, a soda-soap separates, leaving in the liquid chloride of ammonium along with the excess of free ammonia and salt. This reaction is due to the greater solubility of ammoniacal soap in ammoniacal water, and the insolubility of soda-soap in water containing per cent of salt. At first the ammonia combines with the fatty acids, then the sodium contained in the salt takes the place of the ammonia in the soap. An excess of ammonia and soap is essential. 100 parts of tallow require 15 or 20 parts of ammonia, 20 to 30 of salt, and 200 to 300 parts of water (Whitelaw in Chemischen Centralblatt). No. 17, August 24, 1876. Sweden, June 28, between 11 and 12 a.m. The Radiometer of Mr. Crookes.-A memoir read before the Academy of Padua by Prof. F. Rosetti.-The author concludes his paper as follows:-" After the exhibition which I have performed you will be convinced that the radiometer is not an instrument destined merely to attract general attention by reason of its novelty and the curious phenomena which it presents, but that it may serve as a prompt and sensitive thermoscope, and, if used with proper precautions, also as a photometer. It is a novel acquisition for science, both from a theoretical and a practical point of view, and as such it is is capable of many applications." The author then describes a modification of the instrument for the purpose of registering the intensity of the solar radiations. Movements Produced by Light and Heat, and on the Radiometer of Mr. Crookes.-Dr. A. G. Bartbi.— A luminous or thermic pencil which falls upon any body produces a movement due to four causes-(1) Action of the heated sides. (2) Currents of air produced around the heated body itself. (3) Reaction of gases or vapours liberated by heat. (4) Reaction of air heated by contact with the surface upon which the rays fall. On suppressing these causes in the best possible manner, incident light was no longer found to produce attraction or repulsion. These results, however, do not prove that a very feeble impulsive action is not exerted by heat or light. Bulletin de la Société d'Encouragement pour l'Industrie Nationale. No. 33, September, 1876. Report Presented by M. F. Le Blanc on behalf of the Committee of Chemical Arts on a New Apparatus for the Condensation of Liquefiable Matters Held in Suspension in Gases or Vapours.-MM. E. Pelouze and P. Audoin. This apparatus cannot be described in an intelligible manner without the aid of illustrations. (See Comptes Rendus, lxxvii., pp. 819 and 928.) Report Presented by M. F. Le Blanc on behalf of the Committee of Chemical Arts on a New SpectroElectric Tube or "Fulgurator."-MM. B. Delachanal and A. Mermet.-This interesting paper also cannot be made intelligible without the two accompanying illustrations. Extraction of Vanillin from the Sap of the Pine.M. Bouquet de la Grye, on presenting to the Agricultural Society of France two samples of vanillin derived from the sap of the pine, made the following remarks:-One of the samples is vanillin in a pure state, whilst the other is prepared for the uses of the confectioner. Vanillin exists in the sap of the pine (Pinus sylvestris) and of the larch. The first attempts at its extraction were made by Hofmann, but on a small scale. The price of vanillin, though high, in consequence of the operations necessary for its extraction and purification, is still lower than that of natural vanilla. The difficulty lies in procuring the sap. For this purpose the trees are felled during the period when vegetation is most active-in May and June-and stripped of their bark. They are then immediately scraped. The product of this operation, collected in vessels of tinned iron, is immediately heated on the spot to prevent fermentation, filtered, concentrated, and allowed to cool and settle. A substance is thus obtained which resembles powdered sugar, and which is known as coniferin. This is a stable compound, and is sent in barrels to Paris, where the vanillin is extracted. Gazzetta Chimica Italiana. Anno vi., 1876, Fasc. v. and vi. Inactive Amylic Alcohol of Fermentation.-Luigi Balbiano.-The author describes sulphamylic acid, and the sulphamylate of baryta, inactive amylic alcohol, inactive amylic chloride, bromide, acetate, and valerate, and inactive valerianic acid. Alkaloid found in Damaged Indian Corn and in Mouldy Maize Bread.-Prof. T. Brugnatelli and Dr. E. Zenoni. The authors consider that the alkaloid in question is the cause of the disease known in Lombardy as "pellagra." MISCELLANEOUS. CHEMICAL NEWS, Sept. 29, 1876 Trade Report for September, 1876, of Gehe and Co., of Dresden.-This price current of chemicals and pharmaceutical products is preceded by some very sound and judicious remarks on modern trade and its customs. The authors consider that England has set a good example in its recent legislation on the adulteration of food and drugs, and hopes that there will be a return to genuineness and solidity now the whole civilised world has seen, to its horror, the results of unfettered sophistication. The Carriage of Explosives.-The British Dynamite Company, Limited, Glasgow, have written letters to the Board of Trade on the above subject. These letters are written as a protest against the conduct of certain railway companies and harbour authorities in refusing to convey or receive for storage any explosive which they may notify that they will not receive. The writer points out that most of the leading railway companies refuse to carry dynamite, and hence its manufacture and use in the United Kingdom is virtually prohibited. He maintains that dynamite, according to the evidence of Major Majendie, "is, on the whole, safer to transport than gunpowder packed in barrels." This refusal to convey dynamite he considers a serious injury to the mining industries of the country, and an obstacle in the way of harbour improvements and other engineering works of public utility. A still greater evil is that there are good grounds for suspecting that dynamite and other explosives are surreptitiously conveyed in passenger trains to a serious extent. It has often struck us as a serious inconsistency that while the sale of poisons is placed under very stringent regulations, that of explosives is practically open. Yet explosives may either by accident or by malice give rise to far more serious calamities than the most malignant poison. We think that the sale of explosives ought to be regulated with great stringency, and that no one ought to be allowed to purchase them without giving proof of his identity, residence, of the purpose for which the substance is required, all these points being registered by the dealer. The custom of miners buying their own gunpowder, guncotton, &c., and storing it in their cottages is most reprehensible, and has given rise to many accidents. Explosives needed in mining should be bought by the employer only, who should be responsible for their safe custody and legitimate employment, and should be served out to the workmen as wanted. In the meantime we are very far from approving of the arbitrary manner in which railway companies refuse to carry certain substances, whilst they convey without scruple goods equally dangerous. KING'S COLLEGE.-EVENING CLASSES. WINTER SESSION, 1876-77. Series of Compounds derived from Ammonaldehyd. -R. Schiff.-The author describes the action of ammonIdehyd on phenylic essence of mustard, the formation of acetyl-phenyl-thiosinnamin, the action of ammonaldehyd on the allylic and ethylic essences of mustard. The for- The Evening Lectures commence on Monday, mulæ given are remarkably sensational. On Gelatin, considered especially in reference to its Reducing Agency.-Prof. G. Bizio.-This paper is chiefly devoted to an examination of the precipitate produced when gelatin dissolved in water is treated with a solution of mercuric chloride in excess. Emission of Nascent Hydrogen from Vegetables. -Prof. E. Pollacci,-Not adapted for abstraction. Action of Certain Reagents on the Principal Organic Colouring Matters.-G. Scurati-Manzoni.-An interesting paper, giving the reactions of colouring matters with certain reagents in a series of tables, too lengthy for insertion. Natural Poisonous Nature of the Human Corpse. -A. Moriggia.-The cadaveric poison may be extracted from the viscera of a body under toxicological examination by methods used for the alkaloids, and may complicate the result. October 9th, and terminate in March. CHEMISTRY-Mr. W. N. Hartley, at 7 o'clock. Mondays and Thursdays. Fee, £1 11s. 6d. ANALYTICAL CHEMISTRY-Tuesday from 7 to 9. Fee, £2 28. Mary's Hospital Medical School, OPEN SCHOLARSHIPS and EXHIBITIONS in St. Mary's NATURAL SCIENCE. The Examination for 1876 will be held on Tuesday, the 3rd of October, and following days. Candidates are requested to call upon the Dean, at 49, Seymour Street, Portman Square, on the morning of Monday, October 2nd, between the hours of 10 and 1, and to bring with them the necessary certificates. For further particulars apply to the Registrar, at the Hospital, or to A. B. SHEPHERD, M.B., Dean of the School. Medical School. St. Mary's Hospital Paddington, W. OPENING of WINTER SESSON, October 2nd, 1876 -Introductory Address by Dr. Wiltshire. SCHOLARSHIPS in Natural Science, Classics, and Mathematics, varying in value from £120 to £20. For further particulars apply to the Dean. A. B. SHEPHERD, M.B., Dean of the School. CHEMICAL NEWS,} Oct. 6, 1876. Some New Derivatives of Anthracen. This was ANTHRACEN When treated with chlorine or bromine, under ordinary circumstances, yields dichlor- or dibrom-anthracen, even if the hydrocarbon be used in excess. shown by Graebe and Liebermann, who found that by treating anthracen under carbon disulphide with only one molecule of bromine, dibrom-anthracen resulted. Dr. Anderson has described, however, a dichloride of anthracen, and also a monochlor-anthracen. There can be no doubt, from the way he produced these bodies, that the first was only ordinary dichlor-anthracen, and the latter I am inclined to believe was a mixture of anthracen and dichlor-anthracen. I thought under these circumstances it would be of interest to make further experiments on this subject, and see if it were possible to obtain some definite monoderivatives containing chlorine or bromine. Dibromide of Anthracen.—A one per cent solution of pure anthracen in carbon disulphide cooled to within a degree or two of o° C. when mixed with the theoretical quantity of bromine dissolved in carbon disulphide, and also cooled with ice, gives a reddish brown fluid, which gradually becomes nearly colourless, and at the same time small white brilliant crystals are deposited: these, when collected, were washed with anhydrous ether, and allowed to dry spontaneously or under the air-pump. They decompose, however, rapidly, and hence good numbers could not be obtained on analysis; but the following combustion, taken in connection with the other facts relating to this substance, shows that it is a dibromide of anthracen. 145 it is difficult to obtain in a pure condition, as it is usually mixed with anthracen and dibrom-anthracen. Pure monobrom-anthracen fuses at 100° C. It is easily soluble in benzol and carbon disulphide, and moderately soluble in alcohol, more so than dichlor-anthracen. It also dissolves in glacial acetic acid. It crystallises in long yellow needles. In fuming sulphuric acid it dissolves with a dirty yellowish green colour, addition of water causing a brown precipitate to separate. When its benzolic solution is mixed with a similar solution of picric acid it becomes red, and on evaporation deposits orangered crystals of the new compound not unlike sublimed alizarin. Dichloride of Anthracen.-When about the theoretical quantity of chlorine is gradually passed into a one per cent solution of anthracen, cooled to about o' C., a white crystalline product separates out. This is the dichloride: it is even more unstable than the dibromide, giving off hydrochloric acid rapidly at ordinary temperatures, and still more quickly when heated. It was therefore impossible to analyse it, but from its decomposition into monochlor-anthracen there can be no doubt about its formula beingC14H10C12. It is also produced by gradually adding the theoretical quantity of bromine to a solution of anthracen in carbon disulphide at the ordinary temperature, and may also be obtained from the mother-liquors from the dibromide of anthracen by distilling off the carbon disulphide and crystallising the residue fractionally; but in both these cases Read before the British Association, Glasgow Meeting (Section B.). This substance is difficultly soluble in alcohol, ether benzol, acetic acid, and carbon disulphide. Monochlor-anthracen.-This is best obtained by fusing the dichloride, the reaction being C14H10C12=HC1+C1H,Cl Dichloride of anthracen. Monochlor-anthracen. The product is purified by crystallisation from alcohol, from which it is deposited in golden yellow flat needles, often of considerable length. It may also be obtained from the mother-liquors of the dichloride, which, however, usually contain a good deal of dichlor-anthracen. It gave the following numbers on analysis:— Theory for C1H,CI. 79'05 4'23 Experiment. I. II. 78.62 4'22 78.75 4'52 Carbon Hydrogen Monochlor-anthracen fuses at 103° C. It is very easily soluble in ether, benzol, and carbon disulphide. It is also easily soluble in alcohol, and moderately so in glacial acetic acid. It dissolves in fuming sulphuric acid with a green colour: addition of water to this solution gives a brown precipitate, but if the sulphuric solution be heated it turns brown, and is then not precipitated on addition of water, and seems to consist of disulpho-anthraquinonic acid. Like monobrom-anthracen, it produces a compound with picric acid, which crystallises in most beautiful tufts of scarlet needles. ON THE PROXIMATE COMPOSITION OF COAL-GAS.* By W. DITTMAR, Professor of Chemistry in the Andersonian University, Glasgow. IN a memoir, "Sur le Gaz d'Eclairage," which he published some months ago in the Comptes Rendus, M. Berthelot reports on a most elaborate proximate analysis of the Paris gas, which brought out the startling result that that gas contained only 37 per cent of heavy carburetted hydrogens, and that these 3.7 per cent included of— 3'0 to 3.5 per cent. .. Benzol .. * Read before the British Association, Glasgow Meeting (Section B.) 146 Proximate Composition of Coal-Gas. CHEMICAL NEWS, Oct. 6, 1876. In other words, the gas was found to contain only about | It is true there is room for a little benzol. To find a 34 per cent of things not diluents, and that these 33 per cent consisted substantially of benzol only. Regarding the experimental evidence adduced, it may suffice here to state that the sum total of heavy carbides was determined by absorption with bromine, and that the volume of the benzol vapour was identified with the contraction suffered by the gas when shaken with fuming nitric acid. From the numbers just quoted it would appear that the Paris gas, as analysed by Berthelot, has quite an exceptional composition, owing perhaps to an exceptional mode of manufacture. This, however, is not the view which Berthelot takes of the matter. He does not hesitate to extend his results as applying substantially to illuminating gas in general, these results, he says, being in perfect accordance with what he had found out long ago regarding the pyrogenic relations of carburetted hydrogens. Now it so happened that at the time when Berthelot's memoir reached me I was just engaged in collecting materials and apparatus for investigating, by synthetical methods, into the extent to which the several constituents of a coal-gas contribute to its illuminating power: I accordingly read Berthelot's paper with the greatest possible interest, and at once decided upon looking into the matter. I will begin by offering some remarks on the manner in which Berthelot tries to account for the fact that all previous coal-gas analysts, instead of his few per milles, invariably found large percentages sometimes as much as 10 per cent, and even more-of olefines. Berthelot's explanation is this:-Until now analysts (in attempting to determine the composition of their olefines) have entirely relied on the eudiometric method of combustion, and "la traduction de leurs resultats par les noms de . est absolument erronée comme repasant sur un simple jeu d'equations algèbriques, calculées dans l'hypothèse de certaines inconnues qui ne sont pas conformes à la realité." Now this, I think, is putting it rather strongly. It is quite true that gas analysts hitherto have not always kept quite alive to the obvious proposition that the combustion of a gas cannot by any means give us more than the quantitative elementary composition of the unit volume, and that consequently the reporting of so-and-so many per cents of ethylen, butylen, &c., is nothing more than a rather clumsy modus of stating the volumes of carbon-vapour and hydrogen in the part condensable by bromine or by fuming oil of vitriol. But is it possible to assume that in the many coal-gas analyses which have been published by Bunsen, Landolt, Frankland, and others, the numbers which to these chemists served as a basis for their calculations should have been so entirely wrong as to enable them to turn into CÂН,” what in reality consisted mainly of C6H6? maximum limit for this potential benzol, let us assume the observational errors had made the carbon too high and the hydrogen too low, and take x=1'1 and y = 1.8, instead of 105 and 2'00 respectively. If we do so we findBenzol.. 0.13 vol. Olefines 0'62 containing Co+Hor C226H4-52 in 2 vols. We see that what was put down by Bunsen as so much of a mixture of C2H4 and C4H8 could not well be assumed to have contained much above 17 per cent of benzol. No doubt if we went to the trouble of re-calculating, in a similar manner, the coal-gas analyses executed after Bunsen's method by Frankland, Landolt, &c., we should arrive at similar results. I prefer passing now to a series of experiments which I made for ascertaining to what extent Berthelot's views hold with regard to Glasgow coal-gas. The first experiment I made was to pass a current of the gas through a long column of nitric acid, of 1.5 sp. gr., into a glass gas-holder, and then to compare the illumi nating power of the product with that of the original gas, a "fish-tail" burner being used in both cases. The flame of the de-benzolated gas was only very feebly luminous, which, at the time, I felt inclined to accept as strong evidence of the absence in the gas of any considerable quantity of olefines; but not feeling quite sure on this point I tried some experiments on the luminosity of synthetically prepared mixtures of hydrogen and ethylen. To my surprise I found that the addition (to 1 vol. of C2H4) of only 3 vols. of hydrogen sufficed to bring down the luminosity to about the level of marsh-gas, while a 10 per cent ethylen flame was no more luminous than that of a Bunsen's lamp! On the other hand, a mixture of benzolvapour and hydrogen, which (by combustion of a measured volume with oxide of copper) had been proved to contain 3 per cent of benzol-vapour (equal in carbon to only 9 per cent of C2H4), was found to give a brilliantly luminous flame. These results render it highly probable that the lightvalue of a coal-gas depends far more on the proportion of benzol than on the proportion of olefines contained in it. This, however, has nothing to do with the question on hand. More nearly related to it is an observation which I made incidentally in preparations of benzolated hydrogen. The 3 per cent gas above referred to had been made by passing hydrogen slowly through a bulb apparatus charged with benzol, and kept at about 18° C. From the bulb apparatus the gas was made to bubble up through water into a gas-holder. Now, according to Regnault's tension determinations, the gas should have contained about 10 per cent of benzol-vapour, and yet it contained only 3 per cent. I could not explain this otherwise than by supposing that the greater part of the vapour originally meter. To test this hypothesis a quantity of benzolated hydrogen, kept over mercury, and proved by combustion to contain 6 per cent of C6H6, was shaken with water and again analysed. The percentage of benzol-vapour was reduced to less than 2. Let us look at an example. Bunsen, in his " Gasometric Methods," gives all the details of a complete analysis of a sample of Manchester coal-gas, in which his "ethy-present had been dissolved out by the water in the gasolen" and "ditetryl" (C4H8) were calculated from the following data:-(After removal of H2S and CO2) II'I vols. of tho gas gave up to fuming oil of vitriol o'747 vol. To determine the carbon and hydrogen in this o747 vol. two combustions were made, viz., one of the original gas, and, secondly, one of the part not condensable by SO3; and from the result it appeared that the "olefines," if burned by themselves, would have given After these experiences I felt convinced that, although coal-gas as it comes out of the retort cannot help containing a considerable proportion of benzol, only very little of this vapour will survive the subsequent processes of purification. And having previously found that Glasgow gas when shaken with bromine contracts about 10 per cent, I had no doubt in my mind that the greater part of this contraction must be owing to olefines. Wishing to determine the exact ratio in the gas between the benzol and the olefines, I tried very hard to find out a quantitative method for their separation from each other; but I did not succeed. That nitric acid of 15 is not the proper reagent for the purpose a few experiments were sufficient to show-some made with pure ethylen, others with synthetically prepared mixtures of this gas with ben |