The Dictionary Of Photography

A True Historic Record Of The Art & Practice Of Photography 100 Years Ago.

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Potassium Permanganate                            Powder Process
in 30 ozs. of water, and add gradually about 9 ozs. of oxalic acid, till, after boiling, the solution is neutral to test paper. Filter and make the resulting solution measure 64 ozs., when a solution of oxalate of potash will be obtained 1 in 4. This salt should not be confounded with the binoxalate or acid oxalate of potash known commercially as salt of sorrel, from which it may be prepared by heating 200 parts of acid oxalate in 1000 parts of water, and add-ing carbonate or bicarbonate of potassium, till a faint alkaline reaction is given, and then adding a few grains of oxalic acid or the acid salt.
Potassium Permanganate (Ger., Ubermangansaures Kali, Kaliumhypermanganat; Fr., Permanganate de potasse; Ital., Permanganato di potassd). KMn04. Prepared by fusing to-gether hydrate and chlorate of potash and black oxide of manganese, boiling the product thus obtained with water, and purifying and crystallising the product. Solubility : 6-3 per cent, in cold, very soluble in hot water; decomposed by alcohol. It is used for intensifying negatives, as a test for hypo, and as an intensifier for carbon prints.
Potassium Sulphide (Gen, Schwefelkalium, Kaliumsulfid Schwefelleber; Fr., Foie de soufre, Trisulfure de potassium; Ital., Pentasulfuro dipotassio). Synonyms: Liver of Sulphur, Sulphurated Potash, Potassium Trisulphide. Made by heating together sulphur and carbonate of potash, the resulting mass being poured out on slabs and broken up. It is of variable composition. Solubility : partially soluble in water, and three-quarters of it by weight soluble in alcohol. It is used for the reduction of residues.
Powder Process. A process much used on the Continent for the production of prints on paper, and in England for trans-parencies on glass. The process is not by any means difficult, and as the results are extremely pleasing and can be obtained in any colour, the process is well worth the attention of amateurs. An organic tacky body, sensitised with bichromate of potash or ammonia, is allowed to dry as much as possible, and exposed to light, when it is found that the tackiness of the organic body disappears in exact proportion to the action of light, and any fine powder dusted on will adhere to the tacky portions unacted upon by light. It is obvious, therefore, that by this means an
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