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Proceedings of the Chemical Society, Vol. 7, No. 102 |
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Proceedings of the Chemical Society, London,
Volume 7,
Issue 102,
1891,
Page 149-154
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摘要:
PROCEEDINGS OF THE CHEMICAL SOCIETY. No. 102. Session 1891-92. November 19th, 1891. Sir Henry Roscoe, F.R.S., in the Chair. Certificates were read for the first time in favour of Messrs. Hugh Brown Collins, West Balgray, Glasgow ; Albert Henry Luckett, Brighton College, Brighton ; James Hill Millar, 13,Waterloo Road, Wolverhampton ; James Alexander Schofield, University of Sydney, Xew South Wales ; Morris William Trewers, 2, Pliillirnore Gardens, Kensington, W. ; Hugh Woods, 11,Archway Road, Highgate, N. The following paper was read :-67. " Iron carbonyl." By Ludwig Mond, F.R.S., and Dr. hanger. The authors have isolated two compounds of iron with carbon monoxide, represented by the formulte Fe(CO)5 and Fe2(CO)7, for which they pyopose the names Ferropentacarbonyl and Diferrohepta-carbonyl.The ferropentacarbonyl is obtained by exposing finely-divided iron in an atmosphere of carbon monoxide at the ordinary temperstme during about 24 hours, and then heating to about 120". A small quantity (about 1gram from lo0 grams of iron) of an amber-coloured liquid is thus obi-?,inecl, of the relative density 1.4666, which solidifies below -21", forming acicular, yellowish crystals. The compound distils uiicliangecl zt 102*8", the vapour having a density of 6.5, that corre-sponding to the formula Pe(CO), being 6.7. It is not acted on by ctilute acids ; nitric acid, chlorine and bromine destroy it ; alcoholic solntions of alkalis readily dissolve it, and form red-coloured solutions, wv'riich rapidly change in contact with air, but from which, as yet, no definite compounds IixT-e lxxn obtxinecl.nifei.rolieptncnr~o~i~-~is obtained by exposing tlic liquid ferropenta- 150 carbonyl to light. It separates in gold-coloured crystals, carbon monoxide being liberated. The crystals are almost insoluble in all ordinary solvents ; they are not volatile, but on heating to 80" they are decomposed into iron, ferropentacar bony1 and carbon monoxide. The crystals are not changed by dilute acids, but are readily a,cted on by nitric acid, bromine and chlorine. Alcoholic potash dissolves them, forming a red solution, very similar to the solution of the ferro- pentacar bon y1. A lechre mas then delivered on '' Colour-photometry." By Captain Abney, C.B., D.C.L., F.R.S. Colour has been usually made the subject of reference to empiric and variable standards, a practice which affords results useless for future reference, and only suitable for present immediate wants. What is required is a reference to numbers which are on some standard scale that cam easily be reproduced. According to the lecturer., the colozw of a body, when viewed in a light oj' standard quality, is known when (a) its luminosity, (b) its hue and (c) itspurity, or the extent to which it is freed from admixture with white light, are known and expressed by numbers. The lunzinosity of a colour can be giwn in absolute nzsinbey by rejewing it to the standard cf white. Thus, if white light fall on a coloured surface and on a surface of some standard white, the luminosity of the former may be expressed in terms of that of the light.It may appear difficult to compare the brightness of two 811c11 surfaces, but as a fact, the comparison is easily accomplished by causing the light falling on the white surface to be rapidly alternately made brighter and darker than that falling on the coloured surface. This can be done by interposing in the beam falling on the white surface rotating sectors with apertures which open and close at will during rotation. The point of equal luminosity can be found by this plan within 1 per cent. Esperiments exemplifying the method were made, the brightness of an orange and of a blue pigment being compared with that of a zinc oxide surface which the author iises as standard mhife.I; was also shown by sending the beams through a trough containing water in which mucin was suspended in minute particles, that the relation only held good for the particular light in which it was measured. Hence the necessity for using a standard light. The luminosity of the light transmitted through coloured trans-lucent bodies was also measured, and the same necessity shownfor the use of a standard light. The standard light recommended was that from the crater of the positive pole of the elrctric light when high illumination was 151 required, or from a petroleum lamp when the illumination need not be 80 intense. The method of measuring the luminosity of light coming through translucent bodies was also shown.A white oblong of paper was placed on a blackened card, a square which occupied half this oblong being pierced in the card, and thus half could be illuminated from the back of the card, and the other half by light from the front by placing a rod in the path of the beam to cast a shadow on the first half. The translucent substance was placed close behind the aperture in the card, and the light illuminating the paper, after passage through the translucent medium, was measured by altering the illumination of the other half lighted from the front. The luminosity of the pure spectrum colours may be v-easured by what the author calls 1,he colour patch apparatus, which is described in the Phil. Trans., 1886, and in his work on " Colour Measurement and Mixture." It essentially consists of a collimator, two prisms, a Ieus, and a camera on the screen of which a spectrum is brought to a focus. This screen is removed for experiments, and a collecting lens used to recombine the spectrum, and to form an image of the last surface of the second prism on a screen some 4feet off.A slide with a slit passed through the spectrum causes the white patch to become a colour patch of monochromatic light due to the particular ray traversing the spectrum slit. The white light with which the colour is compared is obtained from the light coming through the colli- mator and reflected from the first surface of the first prism ; by means of a mirror and lens, it forms a patch equal in size to, and which can be caused to overlap, the coloured patch, or to lie alongside of it.In the first case, a rod placed in the path casts two shadows, one of which is illuminated by the colour and the other by the white light ; rotating sectcrs in the path of the latter allow the luminosity to be compared. The light used is the electric light, an image of the cratler of the positive pole being formed on the slit of the collimator. The luminosity of a colour is not the same when viewed from all parts of the eye. The centre of the eye is that with which observations are usually made ; hence the luminosity should be measured with that part of the retina, and it is advisable that no more than 6' of angular measure from the eye should be compared.The audience were enabled to see the difference in luminosity of a colour rhich was of equal brightness to a certain white when viewed centrally, by shifting the axis of the eye so that the image was received on the retina some 10" away from the centre. The action of the yellow spot was then alluded to. The luminosity of any pigrnenl on paper can be found by rotating it ,with two of the three colours : red, emerald-green and ultramarine. 152 These three make a grey which matches a grey formed of black and white. If the luminosity of the three have been accurakely deter- mined, by substituting the pigment whose luminoflity is required for one of them, another grey can be formed to match a grey consisting of black and white.After measuring the angular aperture of tho sectors, the luminosity is determined by calculation; the result is found to agree with the measurement ma8de by the direct method. This is one of the many proofs that the measure of luminosity obtained in the manner described is correct, and not a mere accident. The colour of a pigment can be referred to the spectrum colozws by measuririg the absorption. In the case of transparent bodies, this is best done by using a double-image prism at the end of the collimator so as to form two Bpectra on the camera screen. By adjustment, these may be caused to be so exactly one over the other, that the same colour will pass through a slit in them. After emergence from the slit, t'he rays from the top spectrum are diverted by a right-angle prism, and caught by another which sends them through a lens on to the screen, forming a patch.Another patch as usual is formed by the rays from the bottom spectrum. By placing the transparent body in the path of one of these rays, the absorption can be measured by equalising the brightness of the patches by the sectors and noting the apertures. The absorption of pigments can be measured in the same way by causing one patch tofall on the coloured surface and the other on t,he standard white. To measure the absorption of pigments an easy plan is to rotate black and white sectors together with variations in the amount of white, and to cause the colour patch to fall partly on them and partly on the pigment.The colour is varied till it is seen that t'he grey disc and the pigment reflect the same amount of light. By both these plans templates can be cut out, which, when ro- tated in the spectrum, give the exact colour of the pigment on the screen; hence this is a reduction of the true colour to absolute numbers, since the colour can be reproduced from a reference to a note book. It is to be remarked that the measures are unaffected by any defect in t'he eye of the observer or by the kind of light in which they mere effected. The mixture in uaryitzg proportions of red, green and violet of the spectrum makes white. This was shown by placing three slits in standard positions in the spectrum, and altering their apertures till a match was made with a patch of white light alongside.Aiiy other colow can be matched by the mixture of the same three colows, as was shown in matching green, blue, and brown papers. Siiice three colours will wake white, and the same three colours will make a match with an impure colour, eveqy colour in nature can eui- 153 dently be matched by mixing not more than two of these colours with a certainproportionof white light ;and if these cdours be red and green, or green and violet, the colour can be matched by one spectrum colour and white light, since there is some intermediate colour which has the same hue as the mixture of these two colours. Hence any colour, except purple, can be referred tg some spectrum colour, together with a certain proportion of white light.In the case of purple the colour may be expressed as white light, from which the complementary colour is eliminated. Hence any colour whatever may be expressed in terms of white light and one spectrum colour, the latter in wave-lengths, and the .former in percentage of 1uminosity. This was shown to be the case by interposing between the silvered mirror which reflected the light coming from the first prism, and which formed the white comparison patch, a plain glass mirror which reflected a small percentage of tAe light on to the colour patch, the amount of which could be yegulated by sectors. Brown paper was placed in the white patch, and the spectrum colour was changed and mixed with the white light till the same colour was obtained.The scale of the instrument told the wave-length, and, by interposing a rod in the path of beams, the proportional luminosities of the spectrum colour and of the white light were determined. A similar match was made by light going through signal-green glass, and the complementary colour of the .light passing through permanganate was determined. Light conziizg through propedy picked specimens of red, blue and green glass, and overlapping, rnny also be made to match a colour. The three glasses covered a square lens, and formed an image on a screen of a circular patch of white light coming through ground glass on a screen. Colours were placed on a white beam alongside, and by aliering the amount of the coloured glasses exposed, matches were made.If the dominant wave-lengths of the colour of these tliree glasses be known, and also the amount of white light mixed withit, these measures can be noted in terms of these three glasses ; and, furt9er, it is possible, by mixing the light coming through the three glasses in various proportions, to obtain a spectrum colour mixed with white light for each such mixture. Hence this is a substitute for the spectrum itself. To show this, three similar glasses were placed over apertures suitably cut in a circular card ; and, by causing these to rotate in front of an illuminated slit a sham spectrum was thrown on the screen in which every colour was present. Any colow carc be yeps.oduced with three Ysotatiny sectow of red, greeib (tnd blue mhen certuin pToportions of white or black, or both, are mixed with one OT other. If the dominant wave-lengfhs and the poportion 154 9f .uihite light mixed are known.of eacli such cotour, the pigment whose colour is to be determined can be expressed in numbers as befol-e, and in terms of spectrunt colours if desired. This was shown by matching brown paper with red, blue and green, a little white and black being mixed with the brown. The importance of using some uniform light was insisted upon throughout, slight deviations in the experiments demonstrating this. In concIusion, Captain Abney claimed to have demonstrated that the reference of colour t’o numbers was not only possible but easy, and that, to chemists especially, the application was one of almost capital importance.Everyone could do 16, and the lecturer bad an instrument on the stocks which WRS not so cumbersome as that shown, but which would answer all purposes, he hoped, when complete. RESEARCH FUND. A meeting of the Research Fund Committee will be held in De- cember. Fellows desiring grants are requested to forward their applications to t,he Secretaries before December 12th. At the next meeting, on Thursday, December 3rd, there will be a ballot for the election of Fellows, the candidates being those whose certificates are puhlished in No. 101 of these Proceedings, issued November 17, 1891. The following papers will be read :-1. “ Phosphorous oxide. Part 11.” By Professor Thorpe and Mr. A. E. Tutton. 2. “ Frangulin. Part XI.” By Professor Thorpe and Dr. A. K. Miller. 3. “ The structure and chemistry of flames.” By Prof. Smithells and Mr. H. Tingle. 4. “ The composition of cooked vegetables.” By Miss Williams. 5. ‘‘ The occumence of a mydatic alkaloid in lettuce.” By T. S. Dymond. 6. “ Some metallic hydrosulphides.” By S. E. Linder and Earold Picton. 7. “ The physical constitution of some solntions of insolub,!e sulphides.” By Harold Picton. 8. “ Solution and pseudo-solution.” By Harold Picton and S. E, Linder.
ISSN:0369-8718
DOI:10.1039/PL8910700149
出版商:RSC
年代:1891
数据来源: RSC
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