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The photographic news
- Bandzählung
- 27.1883
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- 1883
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- Hochschule für Grafik und Buchkunst Leipzig
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- Bandzählung
- No. 1271, January 12, 1883
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The photographic news
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Band 27.1883
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- Titelblatt Titelblatt I
- Register Index III
- Ausgabe Ausgabe 1
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Band 27.1883
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lu- on or 1119 at at wn of ied ere pi- pi- pi ed r 6 • cid is er- lu- ut , a the sial r is to ng ric gh ric ter am idy ict, ar’s C. ' O) hly >rt- ing mg ga- , of ■ an- ilar er- in ler- ton in in- ' ive- this 0per iling And reagents were found to act as follows :— “ Ammonio-copper Reagent.—These fibres, without excep tion, dissolve more or less rapidly in contact with metallic copper and strong ammonia. The conflicting impressions which prevail on this point are doubtless referable to the employment of this reagent in its several forms, and to the widely different activities of these. act quickly upon anthracene. The composition of the photogenic substance is also C1H1o, and for this reason it is isomeric, or, rather, poly meric, with anthracene, and termed Paraanthacene. The most singular property of Paraanthacene is exhibited on melting ; the substance then changes back again into ordi nary anthracene, with a melting point of 214° C., and exhibits all the other qualities of the hydrocarbon. It is most likely that the action of the light consists in bringing about a loose combination of several anthracene molecules into a bigger group, the crystals of the Paraan- diagnosing the fibres in regard to the distribution of the lignification, and also of encrusting substances. Neither the Boehmeria, Urtica, nor Linum gives any reaction ; the Ananassa is coloured a uniform faint greenish-yellow; the Yucca and Agave a pale gold ; Hibiscus bright yellow and | streaky; Crotalaria a pale yellow and streaky; and Musa a bright gold, also streaky. “ Aniline Colours.—Asis well-known, the dyeing proper ties of the fibres vary with the lignification, and this appearing to be correlated with the development of phenols, we may hope to be able to arrive at a more correct under standing of this phenomenon. “ In dyeing these fibres with a neutral solution of the so-called alkaline blue, the effects appear to follow an in verse course, the Boehmeria showing the deepest colour, the lignified fibres being much paler. This fact is probably referable to the presence of ‘ pectous ’ substances in the former, and the reaction may prove to be of general use in indicating the presence of acids or acid-forming sub- i stances in the plant tissues.” showed the presence of a body soluble in alkalis and thrown down by acids. It is to be hoped that Messrs. - Cross and Bevan will collect samples of pyroxyline manu factured for photographic use, and for the manufacture of celluloid-like bodies; and institute researches in order to find how far their special characters may depend on the presence of their newly discovered compounds. No doubt our readers could furnish a collection of samples which would materially assist in an investigation of this character. A nother matter which naturally suggests itself in rela tion with this subject, is a study of the decomposition products of the various kinds of nitro-cellulose. At the instigation of Messrs. Cross and Bevan, experi ments have been undertaken by Mr. C. S. Webster on the diagnosis of plant fibres, and we abstract the following par ticulars from the same number of the Journal of the Chemical Society. The following fibres, taken from the Museum at Kew Gardens, were experimented with :— “ Fibro-vascular Bundles of Monocotyledonous Plants.— Agave Americana, Yucca gloriosa, Ananassa sativa (pine apple), Musa Paradisiaca (Manilla), Phormium tenax (New Zealand flax). « Bast Fibres of Dicotyledonous Plants.—Boehmeria puya, Urtica heterophylla (Nilgherry nettle), Crotalaria juncea (Sunn), Hibiscus strictus, Linum usitatissimum (flax), Corchorus capsularis (jute).” Citric Acid (in presence of sulphuric acid). " The substance of all the above fibres is converted by the action of the usual nitrating mixture into so-called nitro-derivatives, allied to the pyroxylins. " In the case of the lignified fibres, the reaction is accom panied by the development of a mahogany-red colour, which on washing gives place to the bright orange of the nitro-derivative in question. “Sulphuric Acid (cone.)—The fibres of Boehmeria and Urtica dissolve to colourless solutions ; the solutions of the others are more or less dark coloured. Chlorine Gas.—Chlorine substitution-derivatives are obtained from the fibre substance of the above fibres, with the exception of the Boehmeria, Urtica, and Linum, the derivatives giving in all cases the characteristic colour reaction with sodium sulphite. “ Aniline Sulphate.—The solution of this substance, as also of the soluble aniline colours, is a valuable aid in A NEW ORGANIC SUBSTANCE SENSITIVE TO LIGHT. It is seldom that a substance is discovered now-a-days highly sensitive to light, although, no doubt, many exist in organic chemistry whose photographic properties are over looked by the chemist. A recent example is anthracene, which behaves in a most remarkable manner in the presence of light. This hydrocarbon, whose formula is CHjo, presents the strange phenomenon that, after exposure to light, its chemical and physical properties change, while its com position remains unaltered. For instance, if a cold saturated and clear solution of anthracene in benzole is exposed to direct sunlight, the solution becomes turbid, and crystals are separated; these latter are much more difficult of solution than anthracene, while they melt at a much higher temperature. Thus, anthracene becomes fluid at 214° C., while the crystals in question are not liquefied until a temperature of 244° is reached. Moreover, after acted upon by light, the resulting body is not so easily affected by reagents—such as nitric acid or bromine— which nient times; and to illustrate this we need only refer to < the manufacture of celluloid, parkesine, and similar sub- 1 stances, and then discuss in detail the photographic 1 aspects of the question. There can be no doubt that col lodion emulsion has been made with nearly, or perhaps quite, all the good qualities of the best samples of gelatine emulsion as now made; but up to the present time the production of such collodion emulsions has rather been a matter of chance than of certainty. The variable element in the making of emulsion has been fully recognised to be the pyroxyline, and only the other day an old collodio- emulsionist, who has gone over to the newer gelatine, opened a cupboard crammed full of packages of pyroxy line, and observed to us, “ Yes, certainly ; gelatine is variable to a certain extent; but if you want trouble, uncertainty, sleepless nights, and failures, intermixed with just enough successes to lead you on, take these in hand.” Observations which we have made when working with pyroxyline convince us that most, if not all, samples of photographic soluble cotton contain at least one of Cross and Bevan’s new bodies; and an experiment which we have just made with several samples in our possession thacene consisting of such molecular groups. A phenomenon still more surprising than that just de scribed was observed a short time ago by Fittig. When experimenting with Isatropa acid,* he discovered an acid containing sulphur of the formula CH1,SO,, or CcH, SO 3 H, which he describes as a very stable powder insoluble in water. The sodium salt, as also the other salts, exhibited a most singular behaviour. The clear aqueous solution becomes turbid after a very little while, and a thick white precipitate is separated. The sensitiveness to light of this sulphur salt is so great that it is almost im possible to keep solutions of the same in an ordinary labor atory for even a short time. In direct sunlight, its decom position is so rapid that freshly-prepared clear solutions made with sodium or barium salts become milky almost immediately, and after a few minutes are filled with a thick flocculent precipitate. The chemical change which here takes place is a very • Liebifs Anna ten, vol. 206, p. 34.
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