ow propos to pass briefly in review the a-tion of development. Generally all the substances which have an energetic tendency to combine with oxygen are capable "f developing the latent image. We have only few inorganic developers, but we have a great quantity of organic substances apt t be used as developers. *Of the inorganic developers the ferrous oxalate is the only important one. Ferrous oxalate is a yellowish salt al insoluble in water but readily soluble 14 solution of potassium oxalate. This liquid is one of the strongest reducers, which only surpassed by some organic sub: tances. In the developing action the ferrous oxala'e is converted into ferric oxalate and at the same time silver is separated. But we cannot ain't to mention a substance that is generally used xs restrainer, that is the potassium bromide, which is used either with this developer or with organic
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