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Pyrocatechin

water, oz and sodium

PYROCATECHIN (Pr., Pyrocatechine ; Ger., Brenzcatechin) Ortho-dihydroxybenzene; known also as oxy phenic acid and catechol. Solu bility, i in of cold water. It was sug gested as a developer in 188o, and came into use in 1899. It occurs in prismatic colourless crystals. It does not stain or fog ; it turns brown in solution and on exposure to air, but its developing powers are not impaired. It can be used with the carbonates or caustic alkalis, either in one or two solutions, and is not influ enced by temperature. The following is a simple one-solution formula for negatives : Pyrocatechin . . 5o grs. 1'5 g.

Sodium sulphite . 12o Sodium carbonate . 24o ,, 55 Water to . . . 10 oz. i,000 ccs.

This is ready for use.

It may be made up in a highly concentrated form, as follows : Sodium sulphite . i oz. lio g.

Caustic soda . . 67 grs. ,, Hot water . . 3 oz. 30o ccs.

Dissolve, and add Pyrocatechin . . 96 grs. 22 g.

Water . . . I oz. Ioo ccs.

For use, diluter part with 15 parts of water. A two-solution formula is : A. Pyrocatechin . 5o grs. z15 g.

Sodium sulphite . i oz. i io Water to . . 10 i,000 ccs.

B. Potassium carbon ate or sodium carbonate . 288 grs. 66 g.

Distilled water to io oz. z,000 ccs.

For use, mix together equal parts.

Sodium tribasic phosphate is recommended by Messrs. Lumiere as an accelerator: A. Pyrocatechin . 96 grs. 22 g.

Sodium sulphite . i oz. i io Water . . . 10 i,000 ccs.

B. Tri-sodium phos phate . . 6o grs. g.

Water . . . 10 oz. I,000 ccs.

Add i part each of A and B to i part of water.

For bromide paper the following one-solution formula is recommended : Sodium sulphite . 6o grs. g.

Sodium carbonate . 120 28 Pyrocatechin . . 20 4'6 Water . . . 10 oz. i,000 ccs, This is ready for use.