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32 BRUNNER, MEANS, AND ZAPPERT July
developing agents, from the first to a second and to a third small dry beaker, and finally to a 400-milliliter beaker. After draining off the aqueous layer, pass the second portion of solvent through the same three small beakers to the 400-milliliter beaker.
Add 100 milliliters of distilled water and 50 milliliters of methanol to the combined solvent layers and titrate potentiometrically with approximately 0.05 normal hydrochloric acid, using glass and calomel electrodes and mechanical stirring. Plot the titration curve of pH versus milliliters of acid and determine the inflection point.
Grams of metol per liter =
6.88 X milliliters of hydrochloric acid X normality of hydrochloric acid.
B. Hydroquinone — After the acid titration add 5 milliliters of one-toone sulfuric acid and 2 drops of 0.025 molar ferroin indicator (ophenanthroline ferrous complex). Titrate with approximately 0.1 normal eerie sulfate solution, using mechanical stirring, until the pink-orange color changes to greenish yellow and remains changed for 30 seconds.
Grams of hydroquinone per liter =
2.20 milliliters Ce(S04)2 X normality Ce(S04)2
grams metol per liter"! 3.44 J
Determination of Diethyl-p-phenylenediamine Chloride
A 25.0-milliliter sample of developer is extracted exactly as described in the procedure for metol. After the addition of 100 milliliters of distilled water, 50 milliliters of methanol, 5 milliliters of one-to-one sulfuric acid, and 2 drops of 0.025 molar ferroin indicator to the combined solvent layers, the solution is titrated with approximately 0.1 normal eerie sulfate solution as described above.
Grams of diethyl-p-phenylenediamine hydrochloride =
4.01 X milliliters Ce(S04)2 X normality Ce(S04)2.
Determination of Sodium Sulfite in Developer A-502
Place a portion of the developer in a 25-milliliter buret. Pipet 20.0 milliliters of approximately 0.5 normal iodine solution into a 250