Fixing process photography

Uses. The principal use for sodium thiosulfate continues to be as fixative in photography (qv) to dissolve undeveloped silver haUde from negatives or prints. In appHcations where rapid processing is requited, such as the processing of x-ray film, sodium thiosulfate has been largely replaced by ammonium thiosulfate. 

Soda niter or sodium nitrate (NaNO ) is the most abundant of the nitrate minerals. It is used for fertilizer, explosives, and preservatives. The natural deposits are located in northern Chile, which was the original source for many years. More recently, nitrogen fixation, which extracts nitrogen from air, has been used for producing sodium nitrate. This synthetic process has greatly increased the availability of this useful sodium salt by ehminating the need for the natural source. It is used to preserve and cure meats and is used in photography, in pharmaceuticals, and as a color fixative in fabrics. 

Many toning processes in photography involve the use of selenium compounds.6 One such process recently recommended consists in treating the print or lantern slide, after developing, fixing and washing, with a solution containing about 1 per cent, of crystalline sodium sulphide and 1 per cent, of sodium selenite or selenious acid after twenty minutes or so in such a bath intense brown tones are obtained with chlorobromide papers, or brown-violet tones with pure bromide papers.7... 

The Kf value for the Ag(CN) 2 complex ion is5.6xl018. Cyanide ions (CN ) would be better removers of silver ions than thiosulfate ions. However, most of us know that cyanide is a deadly poison if inhaled or ingested. In the play Arsenic and Old Lace, it was used very effectively to rid the cast of unwanted characters. Refining the process of film developing, which included not only the discovery of proper fixing solutions but also the development of film surfaces and developers that were reliable, helped to plunge us into the age of modern photography. 

In photography the image defined by the grains of silver is fixed by chemical treatment so that it remains permanent. However, in photochromic glass this process must be reversible—the glass... 

Use Reagent for alkaloids pigments catalyst fixing agent in photography additive in plating processes imparts water resistance to plastics, adhesives, and cement. 

Problem Because the process of black-and-white photography is well-known to students, they may want an explanation on how to fix a photo in the fixing bath. Like in the above experiment (see E9.11) a solid is dissolved by a complex compound, in this case silver bromide is dissolved by the dithiosulfatesilver complex [Ag(S203)2]3 (aq). To prepare the students by using similar but simple reaction, silver chloride is firstly dissolved by an excess of hydrochloric acid [Ag (Cl)2] (aq) ions are formed. 

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