The photographic news

• Bandzählung: 6.1862
• Erscheinungsdatum: 1862
• 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
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• Sammlungen: LDP: Historische Bestände der Hochschule für Grafik und Buchkunst Leipzig
• Sammlungen: Fotografie
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• Strukturtyp: Band

• Digitalisat: SLUB Dresden
• Strukturtyp: Ausgabe

Feb, [Feb. 28, 1862. THE PHOTOGRAPHIC NEWS. 98 A st is so li Nvay: ien vith c the 80 REN Th means Protocl oxidise amoun sets the when t of free water ( of unk chlorid iron. quanti quired is foun solutio evolut smell in the to the series of operations will in most cases be found almost’ tirely free from impurities ; but if need be a third or evel fourth course of fractionizing may be resorted to. It will found far easier thus to separate the extraneous substap® occupie elemen others, markal their ii either 1 the fir an alkali, soda, or potash, usually the former; it dissol in water with a degree of rapidity proportionate to its n ness in alkali. It is prepared by fusing together line w sand or powdered quartz with soda or one of its readily ( composable salts. For all photographic uses a prod* should be chosen containing as much silica as possible, long as it is soluble in water. In no case should there Scientitir Gussiy. PURIFICATION of Water-glass for Photographic Purposes —Action of Silicic Acid on Fermentation—CUErOUS Pro perty of Tellurium-Methyl—New Processes for the ESTIMATION AND DETECTION OF NITRIC AciD IN SOLUTIONS. On many occasions have the peculiar properties of soluble glass been mentioned in these columns, and their adaptation to the wants of the photographer been advocated. As a substitute for collodion, as a varnish, and as a cement, it has repeatedly been the subject of experiments, and it is probable that in one if not all of these characters it would hove found its way into the photographer’s laboratory, were it not for the great difficulty of preparing the compound in a pure state. Soluble glass, or rcater-glass, as it is frequently plain nitrate of silver as given in our quotations, by which means he preserved half tone, and, in his opinion, dis posed of the question we raised respecting the chlorides in the paper, the alkali in excess dissolving the chloride of silver formed. On the latter point we will only stop to ex press a doubt as to whether Mr. Reynolds can dispose of the chloride so easily ; but as regards half tone we gave him full credit for his demonstration. Mr. Taylor’s paper had not, at this time, come under the notice of Mr. Reynolds ; had it done so he would have seen that ammonio-nitrate of silver had been previously employed by Dr. Halleur for the purpose. Nevertheless, to Mr. Reynolds belongs the credit of showing why that salt should be used. Lastly, at pre sent,—for Mr. Shadbolt “ may have something to say on this subject in his next number,”—lastly comes a letter in the British from the originator of this discussion, to the effect that “ no one can be more convinced than he now is that the process is not new,” and, as it is eVer a comfort to have companions in misfortune, he seizes hold of Mr. Macdonald, who, in a letter to the same Journal, as “ the originator of this process more than a year ago,” claims “ honour to whom honour is duethis gentleman he pulls with him to the bar of photographic opinion. The true state of the question then, appears to be that printing with peroxalate of iron and the subsequent appli cation of silver, was introduced by Sir J. Herschel; but that Mr. Reynolds, without any knowledge of the process having been known previously, gave us the results of his re discovery in good faith. Mr. Shadbolt, overlooking that among the many suggestions for printing without hypo sulphite of soda being required as a fixing agent, this particular method had more than once been named, and perhaps being struck by the lucid manner in which Mr. Reynolds gives his information more forcibly than by previous communications; comments thereon, and gives his friends the chance, as he says, of “waking up the editor.” Mr. Reynolds being subsequently convinced that the pro cess is not new, frankly states as much, and gives per fectly unnecessary proof that he made his researches quite independently of what had been published before. In conclusion, we may state that the probable usefulness of the method stands in exactly the same position as it did. It has never been shown that it could practically be em ployed in photography, and we trust that Mr. Reynolds will not discontinue his experiments because it happens to have turned out the process is not all his own. The discovery of Dr. Phipson given in a recent number of the News cannot be considered the same as the above, as this gentleman states it to be: one is a silver, and the other an iron printing process. As a method of obtaining a positive print in iron it is simply a rediscovery of Mr. Burnett’s process which appeared a few years back, simul taneously with one we published. The salt of iron which Mr. Burnett preferred as a sensitizer was the ammonio- oxalate, whilst that employed in our experiments was the ammonio-citrate. Michael Hannaford. more than two equivalents of alkali to three equivalents — silica : a glass, of this composition will be very slow to d and in solve; a more basic salt will have a tendency to deli ques is so li Mr. J. M. Ordway has recently devoted some consideral society attention to the different kinds of water-glass, and has disate covered a very perfect means of purifying the compot? salts ( from the different saline and earthy contaminations wli the fa it is sure to contain when prepared for commercial purpo stop, on the large scale. He finds that by several properly c introd ducted precipitations with alcohol, the impurities ma/, not he entirely got rid of. We have therefore in this proceq want 0 ready means of obtaining a water-glass of the utmost put its em and of almost any required composition. For the prep* 11 ft is tion of a perfectly pure substance for delicate experimev ascerta it is recommended that a rather dilute solution of a crt‘ tion. silicate be taken, containing not more than ten per cent solid matter. To ten parts of the liquid may be added, first one part by weight of strong alcohol, and before filterl This hi the mixture should be allowed to stand several hours, fray order to give the reluctant precipitate a chance to get fu the am aggregated together. Rejecting this first deposit, wb has not contains most of the earthy matters and very little of ’ alkaline silicate, add to the filtrate twenty parts of alco and the greater part of the water-glass will be thrown do* 1 When the product is rich in silica, it is quite volominou first, but gradually contracts and becomes more or 1 then ar coherent. After a rest of six hours or more, the alcobo from a roughly made silicate than to observe the many p" cautions required in preparing a pure product with P‘ ingredients ; and considering the small quantity of alcol, required, and the means of recovering even this by dis/ lation, the cost appears so moderate that a manufact" Alnmin might be warranted in resorting to a single precipitat ''hen when a nice water-glass is wanted for use in the arts; immor such a case it will do to operate on a tolerably strong so he tion, say one containing twenty per cent, of solid rnatw but it should be observed that weaker liquors allow o’ called, is a chemical combination of silica with an excess by an lately , » origin ‘ then d more intimate commingling of the alcohol, and are 1 heT d likely to retain the foreign salts ; therefore for photograph. • e< purposes the substance should be prepared from a ten f cent, solution, as above described. !■ Whilst upon the subject of water-glass, we may ment a very curious and important observation, which has j been made. It has been found that silicic acid precipito" from water-glass produces fermentation in saccharine sol tions, particularly after the addition of some tartaric aC and generates the odour of beer-yeast, afterwards of fr! and finally of ether; in very dilute solutions the odotre putrid yeast appears. Silicic acid does not lose this Po perty by boiling with water, or by repeated employment0 most fermenting, and subsequent washing with water. A solut tion 1 of sugar, containing alcohol and tartaric acid ferments brisp photo with silicic acid, evolving carbonic acid gas amidst the S6 actual ration of a yeasty foam. If confirmed, this observation^ Lcuch’s will prove most important to the student ot obscure phenomena of fermentation. liquid being carefully decanted, the solid silicate may spread on absorbent paper, and allowed to drain as long, it will remain without adhering to the paper. The v of a so thus deprived of mother-liquor can then be dissolved in fo 8mall < times its weight of water, and carried through the s" hyposu round of treatment as before. The result of this secd a know