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The photographic news
- Bandzählung
- 7.1863
- Erscheinungsdatum
- 1863
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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. 256, July 31, 1863
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Zeitschrift
The photographic news
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Band
Band 7.1863
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- Titelblatt Titelblatt -
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- Register Index 619
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Band
Band 7.1863
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July 31, 1863.] THE PHOTOGRAPHIC NEWS. 365 fresh precipitation of peroxide of manganese will be preci pitated. Separate this by decantation, and leave the solu tion to crystallize by cooling. When all the crystals have deposited, pour the supernatant liquid off, and wash the crystals with a small quantity of cold water; dissolve them in the smallest possible quantity of boiling water, and leave the solution to crystallize on cooling. In this manner needles are obtained three-quarters of an inch in length, and amounting in weight to about a third of the peroxide of manganese employed. In order to avoid the unavoidable losses arising from decanting the solutions, they may be filtered, employing a funnel having its neck stopped with asbestos. Permanganate of potash crystallizes in dark purple needles having a sweetish taste ; it docs not alter the colour of test papers, and is not deliquescent. When heated, the crystals decrepitate, evolv ing oxygen. As might be supposed from the great amount of oxygen they contain, friction in a mortar with substances greedy of oxygen, such as phosphorus, sulphur, &c., pro duces detonation. Permanganate of potash dissolves in 16 parts of water at the common temperature, forming a purple solution. . When potash is added, this colour changes, through violet and blue, to green. When ammonia is added to the solution, its hydrogen is oxidized with precipitation of peroxide of manganese. All organic substances exert a deoxidizing action on the solution. Alcohol acts with peculiar rapidity; gum, sugar, paper (as, for instance, when used to filter the solution) act more slowly. Decolori zation also takes place when the liquid is exposed in open ves sels, organic particles falling into it from the air, and carbonic acid at the same time combining with the potash. In puri fying water by means of permanganate of potash, Mr. Condy has pointed out that not only is organic matter removed, but lead is also separated. Every one knows how deleterious, but, unfortunately, how common an ingredient this metal is in water after being stored in lead cisterns. When permanganate of potash is added to water containing oxide of lead in solution, it gives the metal an additional equivalent of oxygen, converting it into binoxide of lead, an insoluble brown powder. In a similar way, iron may be separated from water. The method of testing and purifying water from organic impurities is very simple. Prepare a solution of 10 grains of permanganate of potash in one ounce of distilled water. Take a tumbler of the water to be tested, and add to it, drop by drop, the permanganate solution, until the pink colour which it communicates to the liquid does not disappear on standing. If the water be perfectly pure and free from organic matter, the first drop will produce a permanent pink tinge throughout the whole of the liquid, which no amount of standing will cause to disappear. If common distilled water be used containing the usual amount of or ganic matter, the colouration produced by the first drop will disappear in the course of five or ten minutes, and a brown turbidity will be visible in the liquid. Generally speaking, another drop will be required to render the pink colour per manent. A very good means of comparing the qualities of various waters in respect to their organic impurities is to arrange a series of glasses side by side, each containing a certain quantity, say 10 ounces, of the water, and to add one drop of the permanganate solution to each in rotation, re peating the addition at intervals of five minutes. The number of drops required to be added before the pink tinge becomes permanent will be a very good measure of the rela tive amounts of organic matter present. In employing this process for purifying water in quantity sufficient to employ for photographic operations, the permanganate can be added directly to the water contained in a stone vessel or cistern. An ounce or so of the solution of permanganate may bo added at a time, and the water may bo stirred up with a glass or china rod. A quarter of an hour should be allowed to elapse between each addition of permanganate solution. When the decolorization of the pink water proceeds with difficulty it is a sign that the point of purification is nearly reached, and the addition of the pink liquid may then proceed cautiously, half or a quarter of an ounce at a time. So long as decolorization takes place more permanganate should be added, and the water should eventually have a very slight excess of pink tinge in it. If this purification is employed on a small scale, say one or two gallons only, it can be allowed to remain at rest for a few hours, and then be filtered through clean white filtering paper. This effects two ob jects. It separates mechanically the precipitated peroxide of manganese and other impurities which may have been deposited during the act of purification, and it also removes the last trace of permanganic acid which has purposely been added in excess. If the purification has taken place in a cistern, the deposit may simply be allowed to subside, and the clear liquid can be drawn off. If exposed to the air the pink colour will gradually disappear in a day or two, or it may be at once removed by putting a few lumps of freshly burnt charcoal into the water. Eor all photographic purposes water so purified (except it contains an unusual proportion of earthy or saline impurities) is better than the common run of distilled water ; the small amount of potash salts intro duced in the process of purification being unimportant in comparison with the large quantity of injurious matter separated. Oxtitical Tlotites, THE PRINCE CONSORT MEMORIAL. PmoroanAPIID by Dr. Diamond. Wb are uncertain at the moment we write whether these photographs are intended for publication or for private circulation only. If the latter, it is, we think, matter for regret, as they afford the only means by which the majority of those interested can become acquainted with one of the noblest works in monumental sculpture which this or any country possesses. The fact that a commemorative memo rial, combining the double aspects of a record of the first Great Exhibition, and a tribute to the late Prince Consort, with whose memory that Exhibition will ever be associated, should be erected in what is virtually a private garden, belonging to the Royal Horticultural Society, is matter for general regret, the greater that its chief attractions consist in a series of sculptures which go far to redeem us from the national reproach of inferiority which has attached to so much of our public statuary. The memorial, which is of red and grey granite, is in the general form of a temple, with the base projecting at the four corners, so as to carry four colossal bronze figures representing Europe, Asia, Africa, and America. The whole is surmounted by a colossal statue in bronze of the Prince Consort in the costume of the Master of the Order of the Bath. The figures are by Mr. Joseph Durham, whose original design—which has, however, undergone some modi fication—was selected from amongst those of about fifty com petitors. Nothing can exceed the grandeur of these allego rical figures, which are treated with a freshness and power altogether unlike the old conventional types. America, for instance, is no longer the Red Indian maiden attired as a huntress, but a female figure of European type, at once beautiful and powerful, resting her arm upon the axe which clears the forest to prepare for the progress of civilization. In all the figures there is manifested a careful study of ethnological types, and a rare feeling of the minute as well as the great elements of symbolical expression. Altogether, apart from the powerful individualism and poetically representative character of each figure, they are very fine as sculptures, the masses grand and simple, yet perfect in every detail of artistic truth and finish. Photographers may be proud to claim in Mr. Durham a member of the council of the Photographic Society, To those who are fortunate enough to be familiar with the photographs of Dr. Diamond, it will be quite sufficient to
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