Obrazy na stronie

The Different Aniline-Blacks.

June 20, 1879. acid) to 185° to 190° for such a length of time, till it forms , And that of nitro-benzene on a mixture of aniline and after cooling a dull yellowish, bronze-coloured, brittle toluydinsubstance.


Nitro benzene. At that state most of the aniline is converted into

violanilin, which is obtained pure by neutralisation of the (CoHs - NH2)+(C6H.-CH3-NH2)+{ CoHs - NO}

arsenious and arsenic acid in the melt with caustic soda,

Mauvanilin + water. driving off the un-converted aniline by a current of steam,

H separation of the melted violanilin base from the water (formed by condensation of steam), powdering, and

CH2-C6H4-N-C6H4 drying it. This base is converted with aniline and acetic

=3(H20) acid into the spirit-soluble indulin or its base (as described


N-N above), which is made soluble with oil of vitriol, similarly

I | as the indulin base from magenta refuse.

н н Violanilin is also produced by the action of arsenic acid on aniline hydrochloride, or other suitable salts of pure

If there is no hydrochloride of aniline, or of the mixture aniline; further, by the action of pure nitro-benzene on of aniline and toluydin, and no free aniline or toluydin to pure aniline alone, or mixed with aniline salt, and in be acted upon, then the process must be watched very general by the action of suitable oxidising or dehydro. carefully, and by all means be kept below 190°, else a large genating substances on pure aniline or suitable aniline / quantity of by-produas is formed, much easier than in salts at a temperature of 185° to 190°. Also, for example, the same process without hydrochloric acid.

Even a by a current of chlorine gas into aniline at 180° to 190°, sudden reaction (especially on a large scale) may take and then, on the same principle, with a mixture of nitrate place, producing a rise of temperature by itself up to 140° of aniline with aniline salt, or by a mixture of nitrate of at once, and forming a large quantity of several by. soda with aniline salt in excess, and so on.

products. Therefore, if the temperature should rise above Of course in all these processes some other substances 190° the mixture should be cooled down by a thin stream besides violanilin are coming forth, but the latter will be of water whilst agitated, and by these means the temperathe principal one if the operation is conducted very care

ture should be kept within the limits given above. fully, and the temperature of forming violanilin does not

The conversion of violanilin with or without mauvanilin rise higher than 190°. Above that temperature other de into spirit-soluble indulin is caused by the substitution of compositions take place, and by-products will be formed one, two, or three hydrogen atoms in the violanilin to a great extent-as, for example, triphenylen-diamin. appendant by phenyl. blue, &c.—but which to take into consideration would

ir acetate of violanilin with or without mauvanilin is complicate this paper to an enormous extent. Therefore heated with aniline for blue to 140° to 160°, then ammonia I will only treat on the principal substances formed in the is formed, and the above-named 'substitution takes place, largest proportions by these processes, under the supposi producing in the first instance the mono-phenyl-violanilintion that they are carefully conducted.


Violanilin. As an explanation of the chemical reađions going on in the processes above described I give the following:

H Violanilin is the product of elimination of hydrogen from pure aniline, and simultaneous ccndensation.

C6H4-N-C6H4 Mauvanilin is the product of elimination of hydrogen

(C6H3-NH2)+ 1 and simultaneous condensation of a mixture of two mole

C6H4-N-N cules.of aniline and one molecule of toluydin.

| Both these reactions are represented in the following:

H H н
3 aniline
6 hydrogen = violanilin.

Mono-phenyl-violanilin + ammonia.


C6H4-N-C6H4 3 ,

+ NH3


H 2 aniline + I toluydin - 6 hydrogen = mauvanilin.

In the second stage of the process diphenyl-violanilin is H=

2 aniline + violanilin = diphenyl-violanilin + 2 ammonia.



1 The reaction of nitro-benzene on aniline, or aniline

H hydrochloride, or mixtures of both, is as represented by the

C6H following formulæ :2 aniline + i nitro-benzene = I violanilin + 2 water.


-NCoHz-NH2}+{ CoHs - NO2 102}=




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If that process is carried on so far till the formation of ammonia ceases, then a complete substitution of the hydrogens in the appendants has taken place, and tri. phenyl-violanilin has been formed.

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, } June 20, 1879. Electric Lighting

273 3 aniline + violanilin= triphenyl-violanilin +3 ammonia. hydrochloric acid. After it is dissolved water is added


slowly under agitation to five times the weight of glycerin,

by which means a solution is obtained which can be used C6H4-N-CH

for dyeing. But all solutions of spirit-soluble indulin have 3

the disadvantage that the indulin separates quickly in the C6H4-N-N-H

bath, rendering the dyed shades uneven.

The water-soluble indulins are dissolved in warm water, H

and the solution given in the luke-warm acidulated bath where the goods had been immersed before, and then the bath is heated nearly up to the boiling-point, and kept

there till the desired shades are produced. The water. C6H4-N-C6H4

soluble indulins dye good shades of light and dark greys,

+ 3(NH3) even approaching black, which shade to reach fully offers C6H4-N-N-C6H5 N

some difficulties, so that they are scarcely used for black

dyeing on a large scale; besides, the black, when reached, CóHs

is of a dull and inferior shade, and only slightly resists In the most spirit-soluble indulins the triphenyl- / light, air, and soap.

(To be continued.) violanilin is predominant in quantity; in many of them the

and diphenyl-violanilin and mauvanilins accompany it. Thus, indulin will be principally triphenyl-violanilin

ELECTRIC LIGHTING. hydrochloride :C6H5

The Report of the Select Committee of the House of C6H4-N-C6H4

Commons on Electric Lighting was issued June 18th.

It is as follows:-

The general nature of the electric light has been well

explained in the evidence of Prof. Tyndall, Sir William Co H, H

Thomson, Dr. Siemens, Dr. Hopkinson, and others. It

is an evolution of scientific discovery which has been in By the treatment of these bases and their salts with oil active progress during the whole of this century. Essenof vitriol, as described above, the four conjugated acids tially the electric light is produced by the transformation and their salts may be produced.

of energy either through chemical or mechanical means. Sodium triphenyl-violanilin-mono-sulphonate

The energy may be derived from a natural force, as, for SO3NaC6H4

instance, a waterfall, or through combustion of a material in the cells of a voltaic battery, or of fuel in a furnace.

The energy being converted into an electric current, may 96114-N-C6H4

be used to manifest electric light by passing between carC6H4-N-N-C6H5

bon points, or by rendering incandescent solid bodies, N

such as iridium. A remarkable feature of the electric

light is, that it produces a transformation of energy in a CH

singularly complete manner. Thus the energy of oneSodium triphenyl-violanilin-disulphonate

horse power may be converted into gaslight, and yields a

luminosity equal to 12-candle power. But the same SO3NaC6H4

amount of energy transformed into electric light produces

1600-candle power. It is not therefore surprising that C6H4-N-C6H4

while many practical witnesses see serious difficulties in

the speedy adaptation of the electric light to useful purC6H4-N-N-C6H3

poses of illumination, the scientific witnesses see in this

economy of force the means of great industrial develop. SO3NaCoN.

ment, and believe that in the future it is destined to take And also the tri- and tetra-sulphonates. And, of course, a leading part in public and private illumination. There besides these the corresponding sulphonates of the accom | is one point on which all witnesses concurred, that its use panying compounds are formed simultaneously. The would produce little of that vitiated air which is largely mono-sulphonic acids are insoluble in water, but their formed by the products of combustion of ordinary illualkali salts are easily soluble. The disulphonic acids are

minants. only sparingly, but their alkali salts are easily, soluble. Scientific witnesses also considered that in the future

The tri- and tetra-sulphonic acids, and their salts of the the electric current might be extensively used to transmit phenylated viol- and mauvanilins, are scluble in water, power as well as light to considerable distances, so that the last the most, and these form the principal constituine power applied to mechanical purposes during the ents of the commercial water-soluble indulins, sometimes day might be made available for light during the night. containing some of the nigrosin sulphonic acids or their The Committee only mention these opinions as showing salts.

the importance of allowing full development to a pracThe properties of the spirit- and water-soluble indulins tical application of electricity, which is believed by are very nearly like those of the aniline-blues, and their competent witnesses to have future important bearings constitutional formulæ are also much alike.

on industry. The spirit-soluble indulin dyes wool, silk, cotton, and So far as the practical application of the electric light other fibres grey in various shades, whilst it is difficult to has already gone, there seems to be no reason to doubt dye black shades with. It is dissolved in acidulated alco- that it has established itself for lighthouse illumination, hol (or methylated spirit) by boiling. The filtered solution and is fitted to illumine large symmetrical places, such as is added to the acidulated cold bath, in which the goods squares, publie halls, railway stations, and workshops. to be dyed are immersed, and which is heated up slowly is used in aris lighting shops which require a light to the boiling-point, and kept there till the desired shade by which different colours may he distinguished, and has is reached.

recently been used in England for the same purpose with The spirit-soluble indulin dissolves at about 115° in satisfactory results. Many trials have been made for 2 to 3 parts of its weight of glycerin containing 5 per cen. street illumination with greater or less success.


CHEMICAL NEWS, 274 Sensitiveness of Electric Discharges in Vacuum Tubes.

June 20, 1879. Compared with gas, the economy for equal illumination should have full powers to use the electric light for purdoes not yet appear to be conclusively established. poses of public illumination, and that the Legislature Although in some cases the relative economy for equal should show its willingness, when the demand arises, to candle power is on the side of the electric light, yet in give all reasonable powers for the full development of other cases gas illumination of equal intensity has the electricity as a source of power and light. advantage, Unquestionably the electric light has not made that progress which would enable it in its present condition to enter into general competition with gas for the ordinary purposes of domestic supply. In large esta- PROCEEDINGS OF SOCIETIES. blishments the motors necessary to produce the electric light may be readily provided, but, so far as we have received evidence, no system of central origin and distri.

PHYSICAL SOCIETY. bution suitable to houses of moderate size has hitherto been established.

Ordinary Meeting, June 14, 1879. In considering how far the Legislature should intervene in the present condition of electric lighting, the Committee

Prof. W. G. ADAMS, President, in the Chair. would observe, generally, that in a system which is developing with remarkable rapidity it would be lamentable if New members :-Mr. Donald Macalister, B.A., and Mr. there were any legislative restrictions calculated to inter. St. George Lane Fox. fere with that development. The Committee. however, Prof. MACLEOD described a plan for Suppressing the are not in a position to make recommendations for condi. Induction Disturbaaces in a Telephone Circuit. It is tions which may hereafter arise, but at present do not known that a secondary battery, composed of metal plates exist, as to the distribution of electric currents for lighting and sulphuric acid, allows weak currents to pass while private houses from a central source of power. No legis- stopping those of high tension. Prof. Macleod therefore lative powers are required to enable large establishments, inserted a secondary battery of platinum plates between such as theatres, halls, or workshops, to generate electri: the line and the telephone, but this stopped both the incity for their own use.

duction and the vocal currents. When platinum wires íf corporations and other local authorities have not were substituted for the plates, however, the indu&ion power under existing statutes to take up streets and lay currents were stopped, while the vocal currents could be wires for street lighting and other public uses of the feebly heard. electric light, your Committee think that ample power Dr. O. J. Lodge exhibited his New Reversing Key for should be given them for this purpose. There seems to Electrometer Work, which is preferable to the ordinary be some conflict of evidence as to whether the existing forms, as giving a high insulation, small capacity, and not powers are sufficient or not. But even in regard to local requiring the hand to approach close to it to work it. It authorities it would be necessary to impose restrictions consists of four platinum wires, arranged in pairs crossing upon placing the wires too near the telegraph wires used one another; one pair crossing between the other two. by the Post Office, as the transmitting power of the latter These are the terminals and contact pieces of the key. would be injuriously affected by the too close proximity The middle pair are supported by an endless silk thread, of the powerful electric currents needed for producing which runs on two pulleys, one of which is fitted with a light.

handle. On turning the handle to right or left the two Gas companies, in the opinion of the Committee, have middle wires are brought into contact with one or other no special claim to be considered as the future distributors of the two outer wires, and the current reversed at will. of electric light. They possess no monopoly of lighting The whole is enclosed in a metal box. public streets or private houses beyond that which is given Mr. J. F. Moulton then demonstrated the results of to them by their power of laying pipes in streets. Electric the experiments of Mr. Spottiswoode and himself on the light committed to their care might have a slow develop- Sensitiveness of Electric Discharges in Vacuum Tubes. ment. Besides, though gas companies are likely to benefit These experiments were undertaken to find the cause of by the supply of gas to gas-engines which are well suited the luminous layers or strata in the discharge, a Holtz as machines for producing electric light, the general pro- machine being employed. It was observed that when cesses of gas manufacture and supply are quite unlike feeble currents were drawn from the machine, the disthose reeded for the production of electricity as a motor or charge could be depressed by laying the finger on the illuminant.

tube, and this depression always occurs with intermittent The Committee, however, do not consider that the time currents; therefore the feeble currents from a continuous has yet arrived to give general powers to private electric current Holtz discharge themselves like intermittent companies to break up the streets, unless by consent of currents by reason of their feebleness. This sensitiveness the local authorities. "It is, however, desirable that local of the discharge to the approach of the finger was found authorities should have power to give facilities to com- to be due to the conductivity and electric capacity of the panies or private individuals to conduct experiments. hand. Electricity, opposite in kind to the discharge, is When the progress of invention brings a demand for induced on the finger, and streaming upon the tube facilities to transmit electricity as a source of power and neutralises part of the discharge therein. This effect was light from a common centre for manufacturing and also shown by means of tinfoil rings round the tube. An domestic purposes, then, no doubt, the public must re- intermittent current is of course capable of this static inceive compensation advantages for a monoply of the use duction on neighbouring conductors. The luminous of the streets. As the time for this has not arrived, the discharge in a vacuum tute consists of a bright sharp Committee do not enter into this subject further in detail glow at the negative terminal, followed by a dark space, than to say that in such a case it might be expedient to then a hazy bluish light at the positive pole. The strix give to the municipal authority a preference during a or layers in these sensitive tubes merely repeat this aplimited period to control the distribution and use of the pearance. They can be artificially produced by placing electric light, and failing their acceptance of such a pre- the fingers, or rings of metal, at intervals along a tube ference, that any monoply given 10 a private company conveying an amorphous discharge ; for in this case the should be restricted to the short period required to induced electricity discharging itself from the fingers, remunerate them for the undertaking, with a reversionary breaks up the amorphous discharge into dark and bright right in the municipal authority to purchase the plant layers. In these stratified discharges the electricity and machinery on easy terms. But at the present time appears to travel per saltum, or by stepping stones, as the Committee do not consider that any further specific one may say, and the glow seems to be a molecular recommendation is necessary than that the local authorities structure, a view which is supported by Mr. Crookes's

June 20, 1879.
Organic Chemistry.

275 experiments. A negative discharge from the finger pro- , occupies no less than one-third of the whole volume. A duces a dark space in the tube discharge, and a positive student, therefore, who learns by rote a good selection of one a bright line; therefore, one can tell the kind of dis. these answers runs a fair chance of passing, though his charge passing in a tube by laying a finger on it. If the real knowledge may be of the most fragmentary and imsame pole be brought to both ends of a tube a discharge perfect kind. As practical examinations are to a certain will still take place from each end, and there will be a extent free from the objection which applies to written dark space in the middle; the electricity here seeming to examinations, it is to be hoped that in the future much turn back again the way it came. The discharge from a greater stress will be laid on practical work than has pole through a vacuum tube would therefore appear to be hitherto been the case. In the meantime it is highly not akin to conduction but to a disruptive discharge. It satisfactory to know that the Department is alive to this is a leap in the dark, and the phenomena observed are due necessity, and to find that a large percentage of the candito the gaseous nature of the medium. These experi- ; dates in practical chemistry at these examinations send ments point to the possibility of completing a circuit by up very creditable results, showing that at many science positive electricity alone.

schools a really sound knowledge of chemical analysis is Prof. GUTHRIE suggested that by combining vacuum being imparted. tubes with the induction balance of Prof. Hughes it might As regards the book itself it is difficult to imagine how be possible to get an optical balance for measuring induc- anyone who professes to be a teacher and to have ex. tive capacity.

perience enough to write a text-book on the subject could Dr. HENRY DRAPER, of New York, who is now on a employ the arrangement adopted by the author. In visit to England, then addressed the meeting on his many cases compounds are classed together which have alleged discovery of oxygen in the sun by bright lines in little or no connection with one another; thus, under the the solar spectrum. He said that hitherto he had not heading of hydrides of organic radicals we have in the been able to find these lines projecting from the limb of following order :-Hydrocarbons, cyanogen, oxalic acid, the sun like hydrogen, and his impression is that oxygen oxamic acid, oxamide, hydrocyanic acid, formic acid, and resides lower than the reversing layer. He had lately Prussian blue; whilst among urganic bases we have been extending the dispersion of the spectrum of terres. cyanic acid. Nor is his plan of describing the apparatus trial oxygen, and from a light of maximum intensity of employed in organic analysis, &c., to be recommended. one candle power had now got a dispersion of 80 inches This he does in a final chapter quite apart from the from A to 0. He exhibited two of the original negatives description of the processes themselves. Space also is of the solar spectrum, showing the bright lines.

here wasted unnecessarily in giving a figure of an ordinary Mr. J. Norman Lockyer congratulated solar science“ specimen tube" for weighing out the substance for on having so able a worker as Dr. Draper, and remarked analysis, as well as by drawings of two retorts, the differthat is Dr. Draper proved his case for even two or three ence between which it is impossible to see, except that O lines it would be sufficient, considering the variability in the one the neck is turned to the left and in the other of the spectrum of matter under different physical con. to the right. The notation is exceedingly loose and deditions. He also alluded to traces of carbon which he fective, different symbols for the same or an analogous himself had found in the sun by the dark futings in the radical being frequently used indiscriminately, even in the spectrum.

same compound or equation, thusDr. Draper said he did not see why carbon should not C-HOMeOHo+KH=CH Ho+C2H4OKOHO. give both bright and dark lines.

But one of the greatest defects in the book is the almost Mr. Scott exhibited a number of coloured photographs total neglect of the use of structural formulæ, without done after the method of Mr. Albert, of Münich.

which a sound knowledge of organic chemistry can never be obtained by the ordinary student. In many even fundamental points the book is also very imperfect.

General reactions are not made sufficiently prominent, NOTICES OF BOOKS.

and no explanation is given of isomerism and polymerism, nor of the difference between empirical and rational

formulæ. To the glycols and their derivatives five lines A Manual of Organic Chemistry. By Hugh Clements, only are devoted, whilst no special reference is made to of H.M. Civil Service, President

of the Amateur Me: glycerin, erythrite, mannite, &c., except as regards the chanics' Workshops Association, London, and Ledurer identification of glycerin. The relations of the various on Various Sciences at St. Thomas’, Charterhouse, &c. organic

acids to one another and to other compounds are Blackie and Son : London, Glasgow, Edinburgh,' and by no means sufficiently insisted on, nor is any evident Dublin, 1879.

distinction made between primary, secondary, and tertiary

alcohols, nor between the different behaviour of aldehyds The difficulties of an examiner in setting questions, which and ketones on oxidation. The important series of aroshall fairly test the real knowledge of a candidate, have matic compounds are passed over far too cursorily, no of late years considerably increased owing to the large reference at all being made to the ortho-, para-, and metanumber of text-books “adapted” to examinations which positions of the side chains in the derivatives of benzol, have been published, and serve merely to "cram " the &c. Anthracen, naphthalen, and all the other important candidate for the time being, with little or no regard to hydrocarbons and their derivatives, containing more than sound instruction. This is especially the case in respect one benzol nucleus, are omitted altogether, except the to the examinations of the Science and Art Department. identification of naphthalen. In a great measure, it is true, this is the fault of the But it is in the series of exercises given at the end of system which makes the teacher dependent for his re- the book that the author shows his want of proper chemuneration on the passing capabilities of his students, mical training, or he would not set such childish questions and therefore necessitates the use of those text-books as the following, in which and in many others he has which are best adapted for getting his men "through.” | evillently tried in how many different ways he could vary

Such a book is the volume before us, forming one of a the same question :-" What organic substances are large class which has come into being with the rapid soluble in water ?” " What insoluble in water ?" mushroom growth of the system of competitive examina.

" Which are soluble in alcohol ?" " Which insoluble tion, A feature in this Manual which cannot be too in alcohol ?" “Which partly soluble in alcohol ?” strongly condemned is the publication at the end of the “ Which insoluble in water but soluble in hot alcohol ?" book of a series of short answers to all the questions set and so on, through quite a long string of such questions in Organic Chemistry by the Examiners in the Science on solubilities. Then follows a long series of similar and Art Department during the last ten years. This questions on the taste of organic substances, including


CHEMICAL News, Chemical Notices from Foreign Sources.

June 20, 1879. “What organic substances taste peculiar ?"! More | matter, and with the white surfaces both external and inthan one-third of all the exercises consist of such strings ternal, I find that the law holds through a wider range of questions, and would doubtless exercise the poor with the white surfaces external than internal. In a paper student to no small extent. Question (93) would be a which I read before the Physical and Mathematical Seation puzzler in the way of analysis in most cases; it runs as of the Literary and Philosophical Society in April of this follows:-"Make a qualitative analysis of the following year I pointed out the cause of this. As such a method mixtures :-Beef, or inutton, or blood, or milk, or flour, or of colorimetry is, I believe, in practical use, I think it well oatmeal, or potatoes, or rice, or apples, or oranges, or to bring the matter early under notice. The nature of the tea, or coffee, or snuff, or opium, &c.

correction to be applied when the white surfaces are in. There are, however, one or two redeeming points, as ternal may be inferred from the following considerations:the section on “Substitution,” and especially that on The light which illuminates the surfaces has previously

Organo-metallic Bodies," whilst the introduction of a passed through the solution, so that really we are looking special chapter on the identification of organic substances at a coloured disk through a coloured solution. Some -a new feature in text-books on organic chemistry-has allowance must be made for this colouration. Itą and q' long been a desideratum.

denote quantities of colouring matter, and t and t' the lengths of columns, then for external surfaces we may use the formula, qt=q' t'. But suppose the surfaces are in

ternal; then we must add to the lengths of the columns CORRESPONDENCE.

an additional length, which would produce the previous colouration. If the fluids compared do not differ much in

composition an approximate formula isASHES OF WHEAT-BRAN.


The value of x must be determined experimentally by To the Editor of the Chemical News.

comparing white surfaces seen externally and internally. Sir,- In the CHEMICAL News, vol. xxxix., p. 244, there is If the fluids differ much in composition, the corre&ion to an elaborate analysis of the ashes of wheat bran. It seems be applied to the columns will differ a little on each side, to me that it is the play of Hamlet with the character of so that a formula q(t+x)=q' (t'+7) will be necessary. In the Hamlet left out.” In the analysis no mention is made of same paper I have pointed out a method of procedure in phosphate of alumina. As this compound plays so im- colorimetry which, I think, may be serviceable to those portant a part in the analyses of flour and bread it ought commencing experiments, or to those who are not good not to have been left out. I have of late paid some atten: judges of colour, or in the case of colours which are diffition to the analysis of bran from white English wheat, and cult of comparison. I find that it contains

Given two cylinders containing coloured fluids of different Silica


intensities, and we wish to obtain the same tint in both. Phosphate of alumina..


In the stronger solution start first with a tint darker than Phosphate of iron


the other, and approach gradually to it; stop when the The percentage of sulphate of calcium should be 0-256, little too long. Next start in the stronger solution with a

colours seem the same. Probably the columns will be a not 1.9567, as given in Mr. Peckham's analysis.- I am, &c., lighter tint than the standard solution ; approach gradu.

J. Carter BeLL. ally to this limit, and stop when there seems no difference,

probably the column will be too short. Next take the VOLUMETRIC DETERMINATION OF CHROMIUM.

mean of the too columns.

The foregoing remarks apply to colouring matters in To the Editor of the Chemical News.

solution. À method of colorimetry founded on the same

principle is, I believe, applied to turbid solutions. It is SIR, - In the last number of the Chemical Society's Journal very desirable that before general adoption some exhaustive there is the description of a process for determining chro- experiments should be made on the limits of its accuracy. mium, based on the oxidation of chromium oxide by potas. -I am, &c., sium permanganate in presence of sulphuric acid, also

James BottomLEY, D.Sc. described in the Chemical News, vol. xxxix., p. 131. May Irwell Terrace, Lower Broughton, I refer the author (Mr. Sell) to the Chemical News, near Manchester, June 16, 1879. vol. XXV., p. 151, in which I have described the same process for the determination of chromium in chrome iron and steel? The process as described there is in daily use, and gives thoroughly reliable results.-I am, &c.,


Atlas Works, Sheffield, June 10, 1879.



Note.-All degrees of temperature are Centigrade, unless otherwise


To the Editor of the Chemical News.

Comptes Rendus Hebdomadaires des Séances, l'Académie
SIR, -At a meeting of the Literary and Philosophical

des Sciences. No. 21, June 2, 1879.
Society of Manchester, on January 11, 1876, I proposed a
method for estimating colouring matters in solution.

Magnetic Impenetrability of Iron.--J. Jamin.-A
Assuming that if we have in solution in equal bulks of a

concentric thickness of 6 millimetres of iron arrests colourless menstruum the same colouring body, the lengths almost completely the magnetic effect of an external helix. of the columns of fluid necessary to furnish the same

Ultra-violet Limit of the Solar Spectrum.-A. colour are inversely as the quantities of the colouring Cornu.—The utmost limit which the author has been able matter present. Practically the method was carried out to reach corresponds to the wave-length 293. by the use of movable white disks in the cylinders con- Alkaline Amalgams and on the Nascent State.taining the solutions. My experiments showed fair M. Berthelot.—The author remarks that we possess approximations when one liquid did not differ very much hitherto very vague notions on the conditions of molecular in strength from the other. Further experiments were mechanics which determine and regulate the use of made with fluids containing large quantities of colouring alkaline amalgams. He has therefore undertaken their

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