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The photographic news
- Bandzählung
- 24.1880
- Erscheinungsdatum
- 1880
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- Englisch
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- Hochschule für Grafik und Buchkunst Leipzig
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- Hochschule für Grafik und Buchkunst Leipzig
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- Bandzählung
- No. 1161, December 3, 1880
- Digitalisat
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Zeitschrift
The photographic news
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Band 24.1880
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- Register Index 631
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Band
Band 24.1880
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December 3, 1880.] E.THE PHOTOGRAPHIC NEWS. 579 Member 1st CH Member 2nd Member 3rd e parts of the • Continued from page 574. Symbolic expression. The “ At Home” for next week will be, “The Platino- type Company at Bromley Road, Lee.” will be done. Again and again has Mr. Swan put forward his hand to give us a helping hand, and he is not the man to forget his old friends in the hour of his triumph. To Mr. Swan photographers—and especially those situated like our good friends in Brighton—must look for a proper solution of the problem of artificial lighting; and from what that gentleman told his audience last week at the Institute of Civil Engineers, we shall not be kept long waiting. It was due, in a measure, to Mr. Swan’s active co-operation that Mr. Laws, of Newcastle, was able to perfect his simple and ingenious method of artificial illumination by means of gas, and we may well hope that his new electiic lamp —a simple carbon thread heated to a glow by electricity passing through it, the carbon the while being confined in a high vacuum to prevent its combustion or decomposi tion-will confer the same vast benefit on the photo grapher, as it bids fair to do upon the community at large. spectrum of nickel containing a trace of copper is the best, as it gives a very long and nearly continuous spectrum. For purposes of gaining accurate adjustment in the parts of the instrument, and for careful focussing, electrodes of cadmium and so on. A formula which is typical of the whole series is expressed thus : C„H2,+2, where n stands for any whole number. Calculating the precise formula for the tenth nember of the series by substituting the member ten for n, we arrive at C,H22. Certain compounds, termed alcohols, are known which differ from the paraffins by an action of hydrogen being replaced by an atom of hydrogen linked to another atom of hydrogen, such a group of atoms being called hydroxyl. The first member is methylic alcohol, thesecond is ethylic alcohol, the ordinary spirit of wine of commerce. gave the best results, as the lines aie very brightly seen on a fluorescent screen, and are easily impressed on a photographic plate. The method of Stokes was found convenient for the pre liminary examination of substances, focussing, &c. ; instead, however, of using the fluorescent screen which he employed it was found moread vantageous to steep a piece of white paper in a solutionof esculine, or to use a thick piece of uranium glass. The transparency of different kinds of very fine optical glass made by Feil proved this substance to be useless for the construction of any part of the apparatus through which the rays had to pass. The same character must be given to Canada balsam, even when in such thin layers as lie between the surfaces of two lenses cemented together. Fiuor spar and Iceland spar were as diactinic as quartz. A layer of water three inches thick did not intercept the Atomic proportion. C=1 atom H=4 atoms ON THE APPLICATION OF PHOTOGRAPHY TO CHEMICAL RESEARCH* BY W. N. HARTLEY, F.R.S.E., ETC., Professor of Chemistry, Royal College of Science for Ireland, i)tiblin. I SHALL now briefly state the subjects investigated by Prof. Huntington and myself, and afterwards a summary of the results obtained. 1. On metallic spectra and the best means of observing absorption spectra, 2. On the action of alcohols, organic acids, and ethereal salts on the ultra-violet rays. 3. On the absorption spectra of benzene derivatives. 4. An examination! of essential oils. 1. On Metallic Spectra.—M. Soret invented a spectroscope constructed with lenses, and a prism of quartz, and an eye piece of very ingenious construction, with which he was able to see the ultra-violet rays. He repeated these observa- tionsof Dr. Miller, and confirmed his statements with regard to the absorption caused by various substances. In these experiments it was found that a metal which would give as nearly as possible a continuous spectrum would be an advantage in the work, but that the lines of cadmium were well adapted to serve as accurately known fixed points in the spectrum to be referred to. We had carefully investigated certain spectra, such as those afforded by electrodes of magnesium, cadmium, indium, zinc, tin, bismuth, antimony, lead, mercury, silver, gold, copper, platinum, aluminum, iron, and nickel. For general purposes the It will be seen above that the atomic proportions or rela tive weights of the atoms as stated above are—Carbon =12 ; hydrogen =1; oxygen =16, or an atom of carbon weighs twelves times, and an atom of oxygen sixteen times, as much as an atom of hydrogen. One of the first branches of inquiring into the action of organic substances on the ultra-violet rays was intended to show whether each additional proportion of carbon and hydrogen in a homologous series influenced the trans parency of the substances. It is evident that to make the experiments satisfactory, either equal volumes of vapour must be examined, or, knowing how much vapour a certain weight of substance would yield, to take weighed quantities of the substances proportional to equal volumes of vapour. This latter plan was adopted. The result of the inquiry proved that for each increased proportion of carbon and hydrogen there was a definite shortening of the spectrum, also that the eighth member of the alcohol series cut off neary all of the invisible rays of the spectrum. The same effect was produced by the cor responding difference in a homologous series of acids. Now, it is a well-known fact that the greater the proportion Composition in parts by weight. Carbon 12 Hydrogen 4 Carbon 24 Hydrogen 6 rays. Very pure alcohol was very transparent, though not perfectly so. 2. Gn the action of alcohols, organic acids, and ethereal salts on the ultra-violet rays.—A large number of organic substances can be conveniently classed into series of homologous bodies. The first member of a series is the simplest in structure, but all the others are built on the same plan, their differences being gradational and of a very simple character. Each member differs from the preceding one by containing an atom of carbon and two atoms of hydrogen more in its composi tion, that is to say, twelve parts by weight of carbon, and two parts by weight of hydrogen. Thus, taking a series of hydro-carbons called paraffins, several members of which are contained in crude petroleum, equal volumes of the several substances in a state of vapour will contain— Carbon 36 ... C=3 atoms Hydrogen 8 ... H=8 atoms CaHs Difference CH, C=2 atoms H=6 atoms CHe Difference CH Name of alcohol. Methylic Comp sition in parts by weight. Carbon 12 . Hydrogen 4 . Oxygen 16 . Atomic proportion. .. H= 4 .. 0= 1 Symbolic expression. ... CHaOH Difference CH, Ethylic Carbon 24 ... C= 2 ... Hydrogen 6 . .. H= 6 ... C:Hs‘OH Oxygen 16 . .. 0=16 Difference CH, Carbon 36 . .. 0= 3 ... Propy lie Hydrogen 3 . .. H= 8 ... Oxygen 16 . .. 0=16 CH, OH
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