The Dictionary Of Photography

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

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Skiagraphy                                                Sodium Chloride
Skiagraphy. See Radiography.
Sodium Acetate (Ger., Essigsiiures Natron, Natriumacetat; Fr., Acetate de sonde; Ital., Acetato di soda). NaC2H302, 3H20 = 136. Can be prepared by neutralising acetic acid with car-bonate or hydrate of sodium. Solubility : 1 in 3 of cold water, 1 in 1 of hot water ; soluble also in alcohol. It is a slightly alkaline salt, and is used principally in toning.
Sodium Bicarbonate (Ger., Natriumbicarbonat, Doppelt-kohlensaures Natron; Fr., Bicarboiiate de sonde; Ital., Bicar-bonate di soda). NaHC03 = 84. Synonyms : Acid Carbonate of Soda, Hydrosodic Carbonate. Is prepared by passing car-bonic acid gas into carbonate of soda moistened with water. Solubility: 1 in 10 of water; insoluble in alcohol. It is used for toning. It is invariably met with in commerce as a fine impalpable powder, and should not be confounded with the carbonate which is usually met with in crystals. It is far less soluble than the carbonate.
Sodium Carbonate (Ger., Kohlensaures Natron, Natrimn-carbonat, Soda; Fr., Carbonate de sonde; Ital., Carbonato di soda). Na2C03, ioH20 = 286. Synonyms : Washing Soda, Sal Soda, Soda Crystals, Carbonate of Soda. This is prepared by several methods, which depend upon the decomposition of salt primarily. Solubility: 60 per cent, in cold, 445 per cent, in hot water, insoluble in alcohol, and 98 per cent, in glycerine. Heat has no effect upon it, except to drive off the water of crystallisa-tion. The commercial varieties of this salt are very numerous, but there are practically only two which need trouble the photo-grapher ; the one is the ordinary washing soda of commerce, which is of indefinite strength, and usually contains much sulphate, and the other the pure salt, the sodium carbonate, which is the officinal salt of the pharmacopoeia, and can be obtained from any pharmaceutical chemist. This is the only salt which should be used for photography. Tables of the equivalent values of the various carbonates will be found under the heading Equivalence, Chemical.
Sodium Chloride (Ger., Chlomatrinm, Natrinmchlorid) Koch-salz, Edelsalz; Fr., Chlorure de sonde, C/ilornre sodiane, Sel de
588