The photographic news

• Bandzählung: 12.1868
• Erscheinungsdatum: 1868
• Sprache: Englisch
• Signatur: F 135
• Vorlage: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: Hochschule für Grafik und Buchkunst Leipzig
• Digitalisat: SLUB Dresden
• Rechtehinweis: Public Domain Mark 1.0
• URN: urn:nbn:de:bsz:14-db-id1780948042-186800009
• PURL: http://digital.slub-dresden.de/id1780948042-18680000
• OAI: oai:de:slub-dresden:db:id-1780948042-18680000
• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

THE PHOTOGRAPHIC NEWS. Vol. XII. No. 499.—March 27, 1868. CONTENTS. PAGE Sel Clement, or Preservative Nitrate of Silver 145 Dry Plates without Preservative 146 Critical Notices 146 Ventilation of Dark Rooms 148 On Collodio-Bromide. By W. B. Bolton 149 Pictorial Effect in Photography. By H. P. Robinson 150 Researches on Dry Plates. By M. Carey Lea 151 page Photographic Difficulties of an Amateur in South Africa. By Dr. Mann 152 Correspondence—“ Lux Graphicus" on the Wing—Gas or Oil Lamps for the Magic Lantern—Preliminary Coating of Albumen in the Wet Process—Some Experiments with Baths 154 Talk in the Studio 155 To Correspondents 156 Photographs Registered 156 SEL CLEMENT, OR PRESERVATIVE NITRATE OF SILVER. Wb noticed some short time ago the introduction of a new salt of silver under the name of “ Sel Clement Preserva tive Nitrate of Silver,” intended for use in printing. Besides being offered at a price not exceeding three-fourths of that of pure nitrate of silver, it was stated to possess certain specific advantages over that salt, especially in the fact that paper prepared with it would keep sensitive for some time without deterioration. In estimating the economy of any new preparation offered in place of the ordinary salts of silver there is one conclusion at which we must inevitably arrive; namely, that half-a-crown’s worth of the new salt cannot possibly contain more than half-a-crown’s worth of silver; but as it is by no means impossible that this silver may be in combination with other bodies which aid the production of good results with the consumption of a small amount of silver, it cannot be asserted, without experiment, that a new salt is not economical. It is certain, therefore, that a novelty promising desirable results is worthy of trial. We examined a sample placed in our hands, and ascer tained that it contained nitrate of magnesia as well as nit rate of silver, which fact we announced. We then placed a portion of the salt in the hands of a distinguished chemist, who is a member of our staff, for careful quantitative analysis. From his report we learnt that the salts of silver and mag nesia appeared to have been mixed in about equal propor tions. Feeling that it would be unfair to the manufacturer to make known the results of an analysis of his preparation before it had been fairly tested by the public, who might be prejudiced by a statement that less than one half of the new salt consisted of nitrate of silver, we forbore, for the time, to publish the details of our examination, resolving to test the salt in practice, and also to learn the result of other experi ence before making further comment on the subject. A contemporary has, however, relieved us of the necessity for further reticence by having published an analysis, from which it would appear that the example under examination contained only about one-third of its weight of nitrate of silver. It may be fair to the manufacturer and of interest to our readers that we should publish the result of our analysis, which is somewhat more favourable to the purchaser than that of our contemporary. We give it in the form we received it from our analyst a couple of months ago. It is as follows :— “The Sel Clement submitted forexamination is a mixture of salts, somewhat moist, white in colour, deliquescent, and very fusible. Reaction tolitmus paper slightly acid. Itconsistsof— Nitrate of silver ... ... ... ... 46 Nitrate of magnesia ... ... ... 33 Water 21 100 “ The salt contains a trace of iron, but no nitrate of soda, saltpetre, or zinc salt. It is impossible to drive off the water by fusion without decomposing some of the nitrate of mag nesia, which then becomes partly insoluble in water. “ The nitrate of magnesia bears no definite atomic rela tion to the nitrate of silver, its amount standing between one and two atoms to one equivalent of the silver salt.” Our sample, it will be seen, contained 46 per cent, of silver, whilst that of our contemporary is only stated at 34-5 per cent. A somewhat singular circumstance remains to be stated. Dr. Phipson, the English correspondent of the Moniteur de la Photographic, mentions in his letter the fact that the salt which had been recently introduced into this country contained nitrate of magnesia, and makes some comments thereon. The inventor of the Sel Clement, of whom the Editor speaks as a chemist of well-known reputation, writes a long letter to that journal, complaining of what he con siders an unfair criticism of his invention by the English correspondent. With reference to the statement that the new salt of silver is nothing more than a mixture of nitrate of silver with nitrate of magnesia the inventor refuses to enter into a discussion as to whether these two salts com bined exert a more beneficial effect than the silver salt alone, but states that, besides the salts just named, the Sel Clement contains two other substances which are organic, of which one is combined with the silver in the form of a salt, and is slightly sensitive to light, while the other possesses the pre servative principle, and preserves the whiteness of the paper. “ What are these two substances ? ” asks the inventor. “ Seeing that they are organic bodies, it will be difficult to discover their nature by means of chemical analysis, and they can only be detected either by. chance or by researches continued in a certain direction.” After some discussion of the question of novelty, in which he states his conviction that the nitrate of magnesia had never “ been suggested, except for the preservation of sensitive collodion, and not for paper,” he proceeds to defend his right to keep the constituents of his material secret, at any rate, until he has indemnified himself for his labours. He does not pretend to any grand discovery, or seek to obtain honour and glory from his invention; he states that he merely asks for an impartial trial of a material which possesses certain special advantages ; and if the salt fulfils the expectations cf the buyer, he is fully content. He concludes by deprecating the tendency of the photographic world to consider any newly introduced material which is brought under the notice of the public as nothing better than quackery, and refers to the respectability of his agents as testifying to the genuine ness and soundness of his product. The question of the inventor as to the other constituents of his salt assuming the form of a challenge, we felt deserved a reply, and having discovered po indications of organic