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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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- Hochschule für Grafik und Buchkunst Leipzig
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- Bandzählung
- No. 1297, July 13, 1883
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Zeitschrift
The photographic news
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Band
Band 27.1883
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- Titelblatt Titelblatt I
- Register Index III
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Band
Band 27.1883
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JULy 13, 1883.] THE PHOTOGRAPHIC NEWS. 439 fixed and volatile oils, alcohol, ether, chloroform and bisulphuret of carbon. Sulphur melts at 115’5 deg. C. and, when cooling, will under circumstances crystallize in sharp, slender prisms. The crystals formed from a solution of bisulphuret of carbon are octahedric. Sulphur heated to 150 deg. C. ignites, and enters easily into combination with oxygen, metals, and other elements, some of which are very important to the photographer. Of all of these, let us first consider the well known Sulphuret of Potassium, which is formed when carbonate of potash and sulphur in certain proportions are brought to a state of tranquil fusion and allowed to cool. The mass obtained is hard and brittle, of peculiar taste and odour, and of a liver brown colour. Hence its ancient name of hepar sulphur is. It is easily soluble in water, attracts oxygen by exposure to air, and changes gradually into potassium sulphate, when it becomes inodorous and white on the surface. The solution is decomposed by mineral acids, which liberate sulphuretted hydrogen and precipi tate sulphur. Most of the metals in solutions are by it precipi tated as sulphurets. Hence its use to throw down silver as a sulphuret of silver from old fixing baths or other solutions con taining it, and as an intensifier for negatives. Sulphuret of Ammonium is used for similar purposes. It is made by passing a continuous stream of sul phluretted hydrogen through liquid ammonia till saturated. Sulphuret of Antimony and Sodium, or Schlippe's Salt, is also used as an intensifier, often in combination with bichloride of mercury. It consists of large, pale yellow diaphanous tetrahedric crystals. It should not be used when the crystals are covered with a reddish brown surface. Sulphuretted Hydrogen is used as a reagent for the detection of metals. It is obtained by the action of sulphuric acid upon sulphuret of iron. The gas thus set free is either applied direct or when mixed with water. Some of the combinations of sulphur with oxygen are of the greatest importance. Besides sulphurous acid, SO:, and sul phuric acid, S+03, there are known a series of others. Dithi- onous acid, S,0, ; dithionic acid, S,0, ; trithionic acid, S 3 O 5 ; tetrathionic, S,0, ; pentathionic, S,0s, to all of which the photo grapher’s interest need only be directed to the dithionous or hyposulphurous, the sulphurous, and sulphuric acids. Hyposulphurous Acid, S,0,, is formed by heating a soluble sulphite with sulphur, or by the action of sulphuric acid upon metallic zinc and sulphide of zinc. This acid exists in combi nation only, and has not yet been prepared in its free state. Combined with soda it forms the widely-known hyposulphite of soda or fixing soda. 1 his salt is readily made by mixing dry carbonate of soda with powdered sulphur, heating the mixture till the sulphur melts, and stirring the agglutinated mass to bring every particle of it in contact with the air. The sulphuret of sodium first formed is thus converted into sulphite of soda. This is dissolved in water, and the filtered solution being boiled with sulphur becomes sulphite, which salt will deposit in crystals. During the process the sulphuric acid of the sulphite takes up an additional equivalent of sulphur, becoming hyposul phurous or dithionous acid, which forms with the soda hypo- sulphate of soda. This salt is obtained as a by-product in very large quantities, and at enormously low prices, in the manufac ture of soda. The solutions of hyposulphite of soda dissolve all insoluble silver compounds except the sulphuret and that result ing from the decomposition of a silver salt by light. It dissolves iodine, and forms with it iodide of sodium and tetrathionate of soda, and the blue colour of iodide of starch. The photographer uses it to dissolve the silver haloids on plates or paper not acted upon by light; and it is also used as a bleacher in many instances. Its chief use, however, is for the destruction of chlorine when it has been applied to destroy the colour of paper pulp or fabrics. Therefore it is known in commerce by the name of antichlor. It converts the chlorine into hydrochloric acid, which forms with the soda chloride of sodium, and the hyposulphite of soda is changed to neutral sulphate of soda ; either of these substances remaining in the paper of which mounts are manufactured, is not injurious to the photograph pasted upon it. Sulphurous Acid, SO,, occurs occasionally in volcanic exhala tions of gases, but is formed directly by burning sulphur in atmospheric air or oxygen. At the ordinary temperature the acid is gaseous, colourless, and irrespirable, and of the well- known suffocating odour of burning sulphur. It is soluble in water, forming the so-called aqueous sulphurous acid. The great energy of this acid to attract oxygen and form with it sul phuric acid, is proved by its application to prevent putrefaction and fermentation. The so-called sulphuring of wine and cider casks has been carried on for centuries to retard the fermenta tion and acidification of those liquids. Another peculiar property of sulphurous acid is its power to decolourize many pigments. Its use is, however, restricted to the bleaching of animal matter, as wool, silk, feathers, leather, &c., the colours of which are not easily attacked by chlorine, being oftentimes even intensified. Sulphurous acid and sulphite of soda, added to the pyrogallic developer used for gelatine emulsion plates, have of late been introduced into the photographer’s laboratory. Without attempting now to discuss the merits of these additions, it is nevertheless evident that the sulphite of soda prevents, from its properties mentioned above, the decomposition of the pyro gallol. It is further claimed that it gives to the negatives the tone and colour so much admired in a collodion plate. Mr. Berkeley, of England, was probably the first to recommend these accessories to the photographer. Sulphuric Acid, S + O, is absolutely indispensable in the pursuit of all technical and chemical operations. It is one of the most powerful factors of modern industry, and is one of the strongest and also one of cheapest acids known to commerce and the chemist. Whenever weaker acids must be separated or ex pelled, alkalies neutralized, metals or metallic oxides converted into corresponding salts, it is invariably employed. Its manifold applications are equalled only by its enormous consumption. To manufacture sulphuric acid, sulphurous acid is first generated by burning sulphur in atmospheric air, and its higher oxidation pro moted by means of nitric acid. We have seen how easily and energetically sulphurous acid takes up oxygen from all matter con taining it. If sulphur is oxidized with even pure oxygen it will only yield sulphurous acid, but becomes sulphuric acid by sub sequent contact with oxygenous matter. Of all means to oxidize sulphurous acid, nitrient acid is by far the most practical and economical. Nitric acid, NOs, is a combination of 1 eq. (or 14 parts) of nitrogen and 5 eq. (or 40 parts) of oxygen. If 2 eq. of sulphurous acid come in contact with NOg, each one of these will take up 1 eq. of oxygen, thus forming 2 eq. of sulphuric acid, while nitrous acid, NOa, a reddish brown gas, is liberated. Further, when 3 eq. of nitrous acid, which are equal to 3 nitrogen and 9 oxygen collectively, are brought in contact with an abun dance of water, they are decomposed into 1 eq. of nitric acid, NOs, and 2 eq. of oxide of nitrogen, NOa ; this gasis an alogous to sulphurous acid. On combining with oxygen it is immediately changed to nitrous acid, NOs, which, again, is converted by the water present into nitric acid and oxide of nitrogen, and so on ad infinitum. Time being so limited, prevents me giving a detailed description of the mode in which sulphuric acid is manu factured on a large scale. This process, however, is carried on within a system of large leaden chambers, into which the vapours of sulphurous acid are carried and brought in contact with finely- divided sprays of nitric acid. The acid formed is collected at the bottoms of the chambers, and contains then about 66 per cent, of pure hydrated sulphuric acid, a rectification of which is completed in a platinum still. The article thus obtained is commercial sulphuric acid of from 97 to 98 per cent. The photo grapher uses pure sulphuric acid for various purposes : to make gun-cotton, either in combination with nitric acid or with nitrate of potash ; to clean glasses, using either the pure acid, or when mixed with nitric acid or bichromate of potash ; to destroy the viscosity of glutin, when it is necessary to recover the silver from useless bromo-emulsions ; as an addition to photosulphate of iron solution to prevent its oxidation, &o. Of the sulphates we handle daily, let us mention alum, or sulphate of alumina and potash, for hardening gelatine negatives ; chrome-alum as a substratum for gelatine plates; sulphate of copper for various intensifiers ; sulphate of iron, and sulphate of iron and ammonia, the principal agent for the making of collo dion negatives and positives, and again for the production of ferrous oxalate developer : sulphate of potash, as an admixture to ferrotype developer ; sulphate of magnesia, to arrest frilling and puckering of gelatine plates; sulphate of uranium with prussiate of potash as an intensifier, &c. Sulphur, and many of its combinations, you will thus observe, are of great importance to us as well as to most all other trades or manufactures. Sulphuric acid is instrumental to furnish mankind with all possible necessities, comfu: ts, and commodities, for it is used in producing them all, and it i • well to say : the state of industry of a country must be rated at her consumption of sulphuric acid.
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