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cussed in Chapter XIV. Cases are mentioned of surgical operations having been successfully performed without the use of chloroform, the patient being first put into a mesmeric sleep. A most remarkable case of " suggestion" is cited, where a youth is told to warm his arm at a cold stove; he, thinking that the stove is hot, puts his arm too near it, and actually burns himself badly, a severe blister being formed surrounded by a zone of inflammation, just as if it had been placed in close proximity to a hot stove. We think this tale must be taken with a certain amount of salt.

Insanity and sunstroke are treated in Chapters XVII. and XVIII., and in Chapter XXII. we come to the great water question. We are glad to see that the author has no reason to complain of the water supplied by the London water companies; it is probably the best supply in the world, and certainly no other supply is so carefully and constantly controlled and kept up to the highest standard of purity by daily chemical and bacteriological examinations.

A curious and valuable statement is to be found in Chapter XXXI. to the effect that in Normandy, where cider is practically the sole and universal beverage, the medical practitioners have never met with a single case of stone, gravel, or calculus during an experience of over forty years.

The book is well printed on good paper, and will well repay reading.

CORRESPONDENCE.

THE GASES OF THE ATMOSPHERE.

To the Editor of the Chemical News. SIR,-In a Lecture delivered on the 8th of this month, at the meeting of the Pharmaceutical Society, Professor Ramsay is reported to have made the following

statement:—

"Early in 1894 Lord Rayleigh wrote to Nature, announcing what appeared to him to be an anomaly, namely, that whilst atmospheric nitrogen was a little over fourteen times as heavy as hydrogen, nitrogen prepared from ammonia or from other chemical compounds was slightly lighter, the difference being about 1 in 230. No explanation was forthcoming at the time, but Lord Rayleigh talked the matter over with several of his friends, including the lecturer, who had some time before suggested to him, at his request, a method of preparing nitrogen by passing a mixture of air and ammonia over red-hot copper, when the oxygen united with the hydrogen of the ammo. nia, and the nitrogen from both the air and the ammonia passed on. He suggested to Lord Rayleigh that probably atmospheric nitrogen was not as pure as it was supposed to be, and directed his attention to Cavendish's experiments and the residue he had found when combining nitrogen with oxygen. Lord Rayleigh did not at first attach much weight to the suggestion, and thought it more likely that different compounds contained different kinds of nitrogen."

I have on previous occasions noted in your columns the progressive eclipse of Lord Rayleigh by the other member of the binary star of Argon, but I confess I was rather surprised to find him thus finally reduced to the po sition of the dark attendant.

On turning to Lord Rayleigh's account of the same period, given on April 5, 1895, at the Royal Institution, some rather remarkable discrepancies are revealed. Lord Rayleigh stated that, "about this time last year or a little earlier," he had been led, by his own purely physical experiments, to ask himself what was the evidence that all the so-called nitrogen of the air was of one quality? He put that question not to Professor Ramsay, but to his

265

colleague Professor Dewar. "His answer was that he doubted whether anything material had been done upon the matter since the time of Cavendish, and that I had better refer to Cavendish's original paper.' Lord Rayleigh added that he quickly followed Professor Dewar's advice, and found to his surprise that Cavendish had put the question quite as sharply as he could put it himself, and had moreover endeavoured to answer it by an appeal to experiment. He then went on to make it absolutely clear that Professor Ramsay did not appear upon the scene at all until after Lord Rayleigh, acting upon Professor Dewar's information, had found in the experiment of Cavendish the solution of his problem, and had recognised in the Cavendish residue the unknown substance hitherto confounded with nitrogen, whose presence explains the greater density of "nitrogen" obtained from the atmosphere. Hence the evidence of Lord Rayleigh given more than three years ago directly controverts the story Professor Ramsay now tells.

Again, Professor Ramsay says that "early in 1894 Lord Rayleigh wrote to Nature" stating the discrepancy he had found between the weights of atmospheric and chemical nitrogen, and asking chemists for suggestions. I thought it well to verify this reference. Lord Rayleigh wrote no such letter to Nature early in 1894. It was on Sept. 29, 1892, that the letter in question appeared. The correction is important because in his lecture, and still more distinctly in his book on the gases of the atmosphere, Professor Ramsay conveys the impression that this letter immediately led to his "asking and obtaining permission to study atmospheric nitrogen. He tells us in the book that he began this study by passing nitrogen from the air over red-hot magnesium, and that the first weighing of a portion of gas so treated took place in May, 1894. It is obvious that this story loses considerably in plausibility when we know that the letter appeared eighteen months previously.

Did Professor Ramsay before May, 1894, ask and obtain Lord Rayleigh's consent to his concurrent investigation of atmospheric nitrogen? There is no evidence whatever for the statement. The real sequence of events I suggest is as follows:-The letter in Nature in 1892 had nothing to do with the matter except as an ex post facto excuse. In April, 1894, Lord Rayleigh read at the Royal Society a paper "On an Anomaly encountered in Determination of the Density of Nitrogen Gas." At the same time the Smithsonian Institution was offering a prize for the most important discovery in connection with the atmosphere. Professor Ramsay took Lord Rayleigh's proof that there is some inert gas in the air which is not saying a word about it, to isolate and study this body. At nitrogen, and proceeded in his own way, and without the same time-that is, between April and July, 1894experiment, isolated the unknown gas, examined its Lord Rayleigh was pursuing the line of the Cavendish spectrum, and showed it privately to some of his friends. It was when he was thus maturing a discovery practically about the middle of July, came down upon him with made some time before, that Professor Ramsay, probably another set of researches, springing, like his own, from easily be understood that, as stated in Professor Ramsay's the results published by himself on April 19. book, letters passed between them almost daily. The net result was that at the meeting of the British Associa tion, in August, the discovery was announced in their joint names. It will be conceded, I think, that Lord Rayleigh paid heavily for the suggestion made to him two years earlier by Professor Ramsay, that he could ob. tain nitrogen by passing a mixture of air and ammonia over red-hot copper. From the way it is put in the lecture one might fancy that Professor Ramsay invented that bit of text-book knowledge for the occasion.

It can

In his book on the gases of the atmosphere, Professor Ramsay, by dint of a narrative chronologically confused and a judicious abstention from precise dates, managed to convey a general impression that he had done important

266

Chemical Notices from Foreign Sources.

and even decisive work before Lord Rayleigh had got as far as the Cavendish experiment. But he has now gone a step further, and has tried to make it appear that every thing was due to his direct inspiration. If the myth goes on evolving itself at the present rate, Lord Rayleigh will shortly figure as a sort of humble assistant called in by Professor Ramsay to perform the routine work of burning away the nitrogen.

Lord Rayleigh has apparently elected to say as little as possible about the manner in which Professor Ramsay became his collaborator, but he has never admitted the accuracy of Professor Ramsay's version. One thing, however, he is quite explicit about-that the inert ingredient of the atmosphere, isolated by Cavendish, was re-discovered by himself, and recognised as something not nitrogen, before Professor Ramsay had anything to do with the matter. I am, &c., SUUM CUIQUE.

CHEMICAL NEWS,
Nov. 25, 1898.

ferric chloride, and that similar derivatives of benzene homologues, such as toluene, and of bodies with more complex molecules, e.g., naphthalene, are also obtainable. Brominated benzenes also give rise to a series of chlorin. ated substitution products when acted upon by ferric chloride, e.g., the compound C6H4CIBr. parabromochlorobenzene, the chlorination of which is here discussed. The ferric chloride exchanges its chlorine for the bromine of the organic bromide; an unusual phenomenon in the aromatic series, but one which is well known in the fatty series, when the chlorinating agents are metallic chlorides, such as SbC15, PC15, HgCl2, &c. The reaction under dis. cussion is between paradibromobenzene and ferric chlor. ide; more than one product is obtained, each being derived from chlorination of C6H4ClBr(1.4), but that produced in the greatest quantity corresponds to the formula C6BrCl5. Thus there are two stages in the reaction, viz., substitution of one bromine atom and chlorination. It is not yet determined in which order these operations occur. Diketones of the Tetra-hydro-ß-oxazol Derivatives of the Phenylurethanes of certain Oxy-acids.-E. Lambling. The author has demonstrated the production

CHEMICAL NOTICES FROM FOREIGN of urethanes of the general formula—

SOURCES

R–CHO.CONH.C6H5

L

COOR

NOTE.-All degrees oftemperature are Centigrade unless otherwise by the action of phenyl isocyanate upon esters of hydroxy

expressed.

Comptes Rendus Hebdomadaires des Séances, de l'Académie des Sciences. Vol. cxxvi., No. 3, July 18, 1898. Researches on the Relations existing between Luminous Energy and Chemical Energy.-M. Berthelot.-A measure of the light energy transformed into chemical energy is best obtained by investigation of endothermic reactions, including the phenomena of oxidation or of combination, where heat is evolved. The author examines the following endothermic reactions :-Decomposition of (1) nitric acid; (2) pure iodic acid; (3) hydriodic acid; (4) oxide of mercury. Also he makes experiments on the reduction of silver chloride. All these observations take place at ordinary temperatures in—(1) direct solar light; (2) diffused light; (3) darkness. The numbers are given in the various cases.

Anhydrous and Crystallised Sulphide of Magne. sium.-A. Mourlot.-The author prepares amorphous sulphide of magnesium by the action of carbon disulphide on magnesium at a red heat. The crystalline form is obtained from this by fusing it in the electric furnace, or it can also be made by the action of tin sulphide on anhydrous magnesium chlorine. In properties it differs from the amorphous form in being much more stable. It resembles crystalline barium sulphide in most of its reactions. It can, however, be easily distinguished, as it cannot be reduced by carbon.

Decomposition of Barium and Calcium Phosphate by Water at 100°.-Georges Viard.-Varying weights of the phosphate are placed in the same volume of water and kept for five hours in a vessel of boiling water. The liquid is then filtered from the crystalline precipitate which is formed. Both filtrate and precipitate are analysed. It is found that the decomposition becomes more and more slow as the concentration increases. In fact the substance behaves in precisely the same way as when placed in cold water, which action was investigated by Joly; the difference being in the numbers for the ratio of the total phos. phoric acid to the combined acid, the limits being 2 at 15° and 2.8 at 100°.

The Substituent Action of the Halogens upon each other in the Aromatic Series.-V. Thomas.—In a recent publication the author has shown that the whole series of substitution products of benzene, up to the compound C6C16, can be obtained by chlorination of benzene with

|

acids. The free acids are obtained by saponification with
soda and subsequent decomposition of the sodium salt
with acid. On boiling these acids with water, internal
anhydrides are produced of the type-
R-CHO.CON.C6H5

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The author has obtained such diketones from phenyl. urethanes of lactic, trichlorlactic, glycolic, phenylglycolic, and a-oxyisobutyric acids. Descriptions of the properties of these substances are given.

Action of Bromine in presence of Aluminium Bromide on Para-isobutyl-phenol. Remarks on the Bromination of Phenols.-F. Bodroux.-The author has already studied the action of an excess of bromine in presence of aluminium bromide on certain phenols. He now concludes by applying the reaction to a compound possessing a long side chain, viz., para-isobutyl-phenolCH3 C-CH3 C6H4 CH3

OH

A description of the method is given and of the properties of the resulting compound. The melting-point together with the result of an estimation of the bromine it contains show that the principal product is pentabromophenol. Hence the molecule of the isobutylphenol has been split up by the action of excess of bromine in presence of aluminium bromide. The conclusion drawn is that the same rules apply, on bromination, to both hydrocarbons and phenols as regards (1) substitution of the hydrogen atoms of the benzene nucleus, and (2) replacement of the side chainif the latter is attached by (C)iv or (CH)""-by a bromine atom. If, on the contrary, the side chain is attached by

CHEMICAL NEWS,
Νον. 25, 1898.

Chemical Notices from Foreign Sources.

a (CH2)" group it is not destroyed. Thus, in the case of certain phenols, bromination may serve to determine the constitution of the side chain.

Vol. cxxvii., No. 4, July 25, 1898. Determination of Arsenic in Antimony and other Metals.-O. Ducru.-Already inserted in full.

Composition of Phosphorescent Sulphides of Strontium.-José Rodriguez Mourelo.-In a former paper, the author stated that monosulphide of strontium is a non-phosphorescent substance. The object of his present research is to determine what impurities cause it to appear phosphorescent. The sulphide is prepared in two ways:-1. By the reduction of celestine containing calcium sulphate and sodium chloride, in addition to strontium sulphate, by pure carbon. The resulting sulphide phosphoresces with a dull green colour. 2. By similarly treating an artificial strontium sulphate, made by precipitating nitrate of strontium with a solution of sodium sulphate. This sulphide, when pure, gives no phosphorescence, but the phosphorescence begins when sodium sulphide, sodium chloride, and strontium sulphate are added; the proportion of the latter being increased until phosphorescence ceases.

Estimation of Methyl Alcohol in Ethyl Alcohol.— A. Gautier.-The author describes a colorimetric method of detecting and estimating methyl alcohol in ethyl alcohol by means of oxidation. The reactions of the pure alcohols were first studied separately, when oxidised with potassium bichromate and sulphuric acid. Besides acetic aldehyd and acetic acid, the distillation products contained, in the one case ethylal, CH3.CHC2H50, and CH3O in the other, methylal, CH2CH3O In order to distinguish between these two ethers, they were condensed with dimethylaniline. The resulting compounds were

(1) CCH2=(C6H4NCH), which on oxidation

gave a blue coloration, rapidly disappearing under the

influence of heat; and (2) CH2=(C6H4NCH;),, viz.,

-CH3 tetramethyldiamidodiphenylmethane, which on oxidation gave an intense blue coloration, deepening under the influence of heat. By this method, a quantity of methyl alcohol not exceeding o'5 per cent can be detected in absolute alcohol. A source of error is due to the presence of methyl alcohol existing as an impurity in the dimethyl. aniline, and an account is given of the means by which this is avoided.

Berichte der Deutschen Chemischen Gesellschaft.
Vol. xxxi., February 28, 1898.

COOH

267

C4H3O.CH=CC6H5
of this acid CH2O.CH=CCO.C2Ho
also prepared furfuracrolein-acetophenone,—

in silky needles; the piperide

CON.C5H10

He has

C,H,O.CH=CH.CH=CH.CO.C6H5, which crystallises in dilute alcohol in needles fusible at 52-53°; furfuracrolein-acetic acid, in needles of a faint yellow colour melting at 153-154°; and finally, semicarbazide of furfuracrolein, prepared by dissolving 2 grms. of furfuracrolein in water and adding 2 grms. of hydrochlorate of semicarbazide and 2 grms. of acetate of potassium; it crystallises in alcohol and melts at 215-219°. Products of the Reaction of Formic Aldehyd on Gallic Acid.-R. Möhlau and L. Kahl.-By this reaction the authors have succeeded in isolating a substance by heating a mixture of 2 molecules of gallic acid and i molecule of formic aldehyd with fifteen times the quantity of dilute hydrochloric acid (1:5). The substance is a crystallised methylene-digallic acid, difficultly soluble, of which the anhydride, C15H1009, has been analysed, and probably corresponds to the following constitutional

formula

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This acid dissolves in concentrated sulphuric acid with a acid; its alkaline solution takes a red colour when exposed to the air.

yellow colour, turning a cherry red by the action of nitric

On Formaldehyd-trioxyfluorone-dicarbonic Acid.R. Möhlau and L. Kahl.-If we dissolve methylene-di

gallic acid in concentrated sulphuric acid and heat slowly,

the yellow solution takes a green colour at about 50°, then an intense blue; the acid in question, C15H150, appears a colouring matter for mordants. The acetyl-derivative melts at 1405-1415°, at the same time turning brown; its benzoyl-derivative crystallises in alcohol in colourless prisms melting at 250 5-2525°. The tetracetyl derivative is in the form of brilliant flakes melting at 241°.

in the form of a crystalline violet powder, and constitutes

The Final Product of the Action of Chloride of Nitrogen on Dimethylaniline.-W. Hentschel.- The author has previously obtained a compound, C24 H13C19N2, by this method. He now finds that he can obtain the same body more easily by saturating a 30 per cent solution of dimethylaniline in benzene, first with hydrochloric acid, then with chlorine, and finally with an excess of chloride of nitrogen, keeping the whole for some hours away from the light. The crystalline mass thus formed is freed from the ammonium compounds by washing with water, and the aqueous solution is shaken up with benzene, which, on being left, gives a crystalline salt on evaporation. The purified product melts at 117°.

On Fluorescent Bodies.- Br. Pawlewski.-It has been laid down that, besides the anthracene derivatives and those containing sulphur and nitrogen, all fluorescent bodies should also contain a pyronic nucleus surrounded by complex atoms, and a phthalic residue. The author shows that though this theory applies to the combinations of the group of fluorescein, it is not quite the same for many other bodies. He gives as examples resorcinbenzene, allofluorescein, and benzylgaïacol. He has recently prepared a substance which possesses a very ONaSCH-CH<902ONa+C10H2.NH2= strong fluorescence; I part in 31,250,000 through a thickness of 15 c.c. showing a distinct fluorescence.

Products of Condensation of Furfurol and Furfuracrolein.-H. Röhmer.-The author has prepared several products of condensation, among which may be mentioned furalpyruvic acid, C4H3O.CH=CH.CO.COOH, obtained by the condensation of furfurol with pyruvic acid in the presence of glacial acetic acid; furalphenylacetic acid,

Synthesis of the Naphthindol Derivatives.-O. Hinsberg and A. Simcoff.-The easy formation of indolsulphonic acids according to the equation

-он

NH

=NaHSO3+2H2O+C10H6 CHCSO2Na

induced the authors to experiment on B-naphthindolsulphonic acid, and in the endeavour to transform it into the principal derivatives of the series B-naphthindol. They here describe the methods adopted by means of which they have prepared several of these bodies.

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Messrs. John J. Griffin & Sons.-Notice of Removal. -This old-established firm have recently removed from their premises at 22, Garrick Street, Covent Garden, into buildings which have been specially constructed for their work, at 20-26, Sardinia Street, Lincoln's Inn Fields. This has been rendered necessary owing to increasing work, which has demanded larger and more adapted buildings, the workshops in Sardinia Street being considerably extended.

Royal Institution.-The Christmas Course of Lectures, specially adapted to young people, at the Royal Institution, will be delivered this year by Sir Robert Stawell Ball, LL.D., F.R. S., Lowndean Professor of Astronomy and Geometry in the University of Cambridge. The subject will be Astronomy," and the lectures (which will be illustrated by models and the optical lantern) will deal with the sun, the moon, the inner planets, the great planets, shooting stars, and new methods. The first lecture will be delivered on Tuesday, December 27th, at 3 o'clock, and the remaining lectures on December 29th and 31st, 1898, and on Ianuary 3rd, 5th, and 7th, 1899.

The Edinburgh University Chemical Society met on November 14th, when Prof. Crum Brown delivered the Presidential Address. Prof, Crum Brown gave a short sketch of Kolbe's life, and reviewed his work under the following heads:-Sulphone Acids; Joint Work with Frankland on the Nitriles; Relation of the Alcohols, Aldehyds, Acids, and Ketones to one another; Electrolysis of Organic Salts; Oxyacids. He specially pointed out the remarkable originality and independence of Kolbe's work and speculation, and their bearing on modern theories of chemical constitution.

International Exhibition of Electricity.-An International Exhibition of Electricity and the Silk Industry will be held at Como in 1899, to celebrate the centenary of Volta's great discovery, Como being his native city. In this Exhibition the history of a century in the vast field of electricity will be reviewed, and a congress of electricians will discourse on the most recent progress of the science. The silk industry is a trade much developed in Como, and it is considered that it would be interesting to show the application of electric energy to an important series of machine tools. Scientific men and engineers from all parts of the world will, it is hoped, take part in the Congress. The Exhibition will be divided into twelve sections, besides the Honours class.

Electrolysis of Bromides and Alkaline Fluorides. -H. Pauli.-The author has repeated, on the bromides and alkaline fluorides, Ettel's experiments on the chlorides. The law for the formation of hypobromides and bromates appears to be sensibly the same as that which regulates the formation of the hypochlorites and chlorates. On the other hand, the electrolysis of the alkaline fluorides has not given any oxygenated salts. The solution after electrolysis contains peroxide of hydrogen, formed according to the equation

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CHEMICAL NEWS, Nov. 25, 1898

New Edition, prepared to meet the requirements of the New (1899) Syllabus of the London University Matriculation

Examination.

JUST PUBLISHED,

Crown 8vo, 388 pp., Cloth, 4s. 6d.

Chemistry for Schools.

An INTRODUCTION to the
PRACTICAL STUDY OF CHEMISTRY.

By C. HAUGHTON GILL.

and Teacher of Chemistry and Experimental Physics in University Late Assistant Examiner in Chemistry at the University of London, College School. Tenth Edition. Revised and Enlarged by D. HAMILTON JACKSON, B.Sc., Ph.D. (Heid.), Demonstrator of With 100 Illustrations. Chemistry, University College, Bristol.

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A reduction made for a series of insertions. Cheques and Post-Office Orders, crossed "London and County Bank," payable to the order of William Crookes

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MONDAY, 28th.-Society of Arts, 8, (Cantor Lectures). "Acetylene," Complete set (unbound), 17 Volumes, 1842-1859. WEDNESDAY, 30th.-Society of Arts, 8. "Photographic Developers

by Prof. Vivian B. Lewes.

and Development," by C. H. Bothamley, F.R.S.

THURSDAY, Dec. 1st.-Chemical, 8. "Oxidation of Polyhydric

Alcohols in presence of Iron," by H. J. H.
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CHEMICAL NEWS,}

Potassium Ferro- and Ferricyanides as Reagents.

Dec. 2, 1898.

269

portion of the leaf. The leaves of the small English variety of Eucalyptus possess similar properties to the being insignificant in size, comparatively speaking.

THE CHEMICAL NEWS. native product, but in a lesser degree, the rings projected

VOL. LXXVIII., No. 2036.

RUTHENIUM TETROXIDE : AN EXPLOSION. By JAS. LEWIS HOWE,

It may be worth while to call attention to an explosion which occurred recently in this laboratory in connection with work on ruthenium tetroxide. As is well known, the only satisfactory method of obtaining pure ruthenium is that of passing a rapid current of chlorine through a solution of the melt obtained by fusing crude ruthenium with caustic potash and saltpetre. The distillate, which consists of RuO4, is generally received in dilute alcoholic potash, the ruthenium being precipitated as a hydroxide. In the case noted the distillate was collected in a small flask for the purpose of obtaining the RuO4, the excess of chlorine and RuO, being led into dilute alcoholic potash, the amount of alcohol being about 10 per cent. After some 5 grms. of RuO, had been collected the chlorine tube became stopped up, and the alcoholic potash solution sucked back into the flask containing the RuO4. In a moment there was a very violent explosion, the apparatus being completely shattered. The force of the explosion can be judged by the fact that a splinter of the thin flask was driven through a thick glass bottle standing near by, making a hole about 3x1 m.m., but not breaking and hardly cracking the bottle. One is reminded of the acci dent in Deville's laboratory, when nearly 100 grms. of RuO4 in process of distillation exploded with terrific violence. RuO4 is so rapidly reduced by organic substances that, if any considerable quantity is present, the heat of the reaction causes instantaneous decomposition. A drop of RuO, coming in contact with rubber, wood, or many other organic substances, instantly explodes. On the other hand, in the distillation with chlorine, the RuO can be received apparently with perfect safety in dilute alcoholic potash.

The dense black smoke produced when RuO, explodes is readily soluble in hydrochloric acid, and hence probably consists of Ru2O3. When RuO4 in a liquid condition is brought in conta with a lump of sulphur, the latter becomes gradually covered with a black deposit, and in the course of a few moments an explosion takes place. Here the sulphur seems capable of reducing RuO4, a fact

hitherto unnoticed.

Chemical Laboratory of the Washington and Lee University, Lexington, Virginia.

NOVEL PRODUCTION OF VORTEX MOTION.

By C. S. STAnford webster, f.I.C., F.C.S.

WHEN the freshly gathered leaves of the native Eucalyptus tree (Eucalyptus globulus) are ignited. they project vortex rings in considerable numbers in succession, accompanied by a spluttering noise. The best results are obtained by holding the scythe-shaped leaf vertically and igniting the apex,-this being the part where the greatest number of translations are obtained. The leaves experi. mented upon were some very fine specimens of San Remo production.

Possibly in the production of these vortex rings, blisters are first formed by the extrusion of the cuticular tissues, and, on the blisters bursting, air or aqueous vapour is spontaneously liberated, the rings being rendered visible on their contact with the smoke from the burning external

It is of course quite immaterial in the production of vortex rings whether the smoke or vapour be inside or outside the apparatus, as can easily be demonstrated by placing an empty Tait's apparatus (this consists of a box with a large round hole at one end, the other extremity being covered with a tense sheet of caoutchouc) suddenly in front of a dense cloud of ammonium chloride vapour, and striking the caoutchouc sheet at the same moment,a vortex ring is formed, being rendered visible after its translation through the vapour.

The author uses the vapour obtained by heating the solid ammonium chloride, in preference to the usual method in which the two constituents are placed side by side, since the vapour thus obtained is not only denser, and more agreeable to work with, but can be kept under complete control.

If desired to fill the Tait's apparatus with the vapour, the solid is heated in a wide glass tube, one end of which is connected directly with the box by means of caoutchouc tubing, and to the other end a narrow glass tube is at tached, and bent back parallel with the volatilising tube, so that the same flame heats both simultaneously; this narrow tube then terminates in a long caoutchouc tube used for blowing into. By gently blowing into the glass apparatus the respired air is heated, and at the same time drives the volatilising ammonium chloride into the box, which is quickly filled with the vapour.

POTASSIUM FERRO- AND FERRICYANIDES AS REAGENTS.

By ROBERT MELDRUM, F.C.S.

Molybdenum.

K,Fe(CN)6, no result with acid or alkaline solutions, even on boiling.

K4Fe(CN)6, with acid solutions deep brown colour, dis. reliable to the extent of 1 in 50,000, and is very characcharged to a colourless solution by NH,HO. This test is teristic. AsH2S gives with 1 in 50,000 a decided brown colouration; Zn+HCl, no result; Zn+HCI+KCNS, a red colouration; it will be seen that the reagent is a deli cate one. With neutral solutions, on boiling a dirty green precipitate results, which on adding NH HO drop by drop is turned blue, and is latterly dissolved to a yellowish green opalescent solution on the addition of more alkali. Reliable to the extent of 1 in 400, though a precipitate results on boiling with a much weaker solution than this. Either reagent is preferable to sodium hydrogen phosphate.

Cadmium.

K4Fe(CN)6, white precipitate; unchanged on boiling, soluble in NH,HO, insoluble in dilute acids.

K,Fe(CN)6, yellow precipitate; unchanged by boiling, soluble in NH,HO or HCI, insoluble in H2SO4 or acetic acid. The ferricyanide is the more delicate and distinc of the two tests, the precipitate of which, in solutions containing less than than I in 2000, appears white. This I find to be a useful reagent for cadmium salts, and consider it superior to H2S.

Silver. K3Fe(CN)6, brick-red precipitate, changing to dirty yellow colour on boiling, soluble in NH,HO, but insoluble in HNO3.

K4Fe(CN)6, white precipitate, unchanged by NH,HO; turned green by boiling, which is turned brown by NH,HO. The precipitates are not soluble in excess of reagent. Reliable only for strengths up to 1 in 400.

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