The DARKROOM COOKBOOK, Third Edition

BROMIDE (see Potassium bromide)
Pharmacopoeia 179
CALCIUM CARBONATE, PRECIPITATED
Synonyms: Aeromatt, Albacar, Purecal, Precipitated chalk.
Appearance: White, odorless, tasteless powder.
Uses: In gold toning.
Notes: Insoluble in water, slightly soluble in water saturated with CO 2, with increased solubility
in water containing ammonium salts. Dissolves in dilute acids with effervescence.
CALGON
Synonyms: Graham’s salt, Sodium hexametaphosphate, Sodium polymetaphosphate.
Appearance: White fl aky crystals or granules; small, broken, glass-like particles.
Uses: Water softener. Calgon has the property of holding calcium and magnesium salts in
solution, even when boiling.
Notes: This chemical is packaged as Calgon Water Softener.
CARBONATE (see Sodium carbonate)
CATECHOL (see Pyrocatechin)
CAUSTIC ALKALI (see Sodium hydroxide)
CHLORAMINE
Synonyms: Chloramine-T, Chlorazene, Chlorazone, Sodium para-Toluenesulfonchloramide,
Tochloride.
Appearance: White or faintly yellow crystalline powder with a slight chlorine odor.
Uses: As an effi cient hypo eliminator for negatives and prints. Used in very dilute solution (0.2%).
Notes: Slowly decomposes on exposure to air. Should be kept dry and tightly closed. Fairly
soluble in water, decomposed by alcohol.
CHLORHYDROQUINONE
Formulas: 2 Chloro-1,4 dihydroxybenzene; 2-Chloro-1,4-benzenediol.
Trade Names: Adurol, Chlorquinol, C.H.Q. (Edwal).
Appearance: Fine white needles or leafl ets.
Uses: For warm tones on papers, when restrained with bromide.
Notes: A derivative of hydroquinone, chlorhydroquinone was once a mainstay for warm-tone
prints. Unfortunately, it is becoming increasingly hard to fi nd, not because it is not useful as a
warm-tone developing agent, but because it is both expensive and dangerous to manufacture.