Pyrocatechin formulas

Even though it has been in use since 1880 pyrocatechin (catechol) is one of the most overlooked developing agents. The working properties of catechol are very much like those of hydroquinone and it can even be used as a substitute for hydroquinone in many formulae, though it works more rapidly than hydroquinone. 

Pyrocat-HD is a Pyrocatechin/Phenidone-based developer formula that can be used for development in tanks or trays. It is also recommended for JOBO and other rotary type processing in tubes and drums. Although originally meant for sheet film, subsequent use has shown that it is also an excellent developer for use with 35 mm and medium-format films because of its high acutance and tight grain pattern. 

Unless a formula specifically calls for distilled water, in most cases tap water can be used. Even when distilled water is indicated, good quality, filtered tap water will usually suffice. A notable exception is those formulas which call for the use of pyrocatechin (catechol) or pyrogallic acid (pyro or pyrogallol). 

All developers containing pyrocatechin should be mixed with distilled water, whether or not the formula calls for it. 

The formula is given here as three separate working dilutions, 1 1 1 7,1 1 1 11, and 1 1 1 14. For the traditional ABC stock solutions see Chapter 6 Pyrogallol and Pyrocatechin. 

I, 2-Benzenediol Catechin 1,2-Dihydroxybenzene ortho-Dihydroxybcnzene Oxyphenic Acid Pyrocatechin Pytocatechinic Acid Pyrocathechol Pyrocathechuic Acid Chemical Formula l,2-H0CsH40H (ii) Observable Characteristics — Physical State (as normally shipped) Solid Color White Odor None (iii) Physical and Chemical Properties — Physical State at 15 X and I atm. Solid Molecular Weight 110.11 Boiling Point at I atm. 413.9, 245.5, 418.7 Freezing Point 219.7, 104.3, 377.5 Critical Temperature Not pertinent Critical Pressure Not pertinent Specific Gravity 1.344 at 20°C (solid) Vapor (Gas) Density Not pertinent Ratio of Specific Heats of Vapor (Gas) Not pertinent Latent Heat of Vaporization Not pertinent Heat of Combustion -... 

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