Chemicals

In this page, details are given about the most important photographic chemicals.

• Acetic acid glacial. CH₃COOH
  Water clear fluid with stinging smell. Solidifies at temperature bellow 17°C. Corrosive action. Mixes in all proportion with water. Used for stop bath, addition to fixing bath and in uranium intensifier.
• Alum, potash. Aluminium potassium sulphate. Rock alum. K₂Al₂(SO₄)₄·24H₂O
  Colorless transparent crystals or  white powder. Kept in corked bottle. Solubility 1 part in 10–11 parts water. Used as hardening agent, also in hypo-alum toning.
• Alum, chrome. Chromium potassium sulphate. K₂Cr₂(SO₄)₄24H₂O
  Deep violet crystals. Soluble 1 part in 5–7 parts water. Used as hardening agent in hardening fixing formulas.
• Amidol. 2,4-Diaminophenol hydrochloride. C₆H₃(OH)(NH₄)₂·HCl
  White to greyish needle crystals. Soluble 1 part in 25 parts water. Strong developer without alkali.

  Pure amidol is a white powder, but the commercial material is usually gray due to traces of oxidation. Because of its poor keeping qualities in solution, amidol is not used in dilute tank developers, but is widely employed for tray work. The dry powder will stain the hand, but, once dissolved, amidol will not stain hands or film. Because of its great activity it is usually employed in developing solutions that are exactly neutral or slightly acid. It is never used with strong alkali.

• Ammonia. Liquid ammonia. NH₄OH
  Colorless solution of ammonia gas in water, with penetrating smell. .880 ammonia contains 35% NH₃. .910 ammonia contains 25% NH₃. Corrosive and poisonous. It’s used in reversal developers and as blackening agent in intensifying weak negatives.
• Ammonium carbonate. Lump ammonia. (NH₄)₂·CO₃
  White lumps or powder, ammoniacal smell. Keep in glass-stoppered bottle. Soluble 1 part in 4 parts water. Used in special developers.
• Ammonium chloride. Sal ammoniac. NH₄Cl
  White crystalline powder. Soluble 1 part in 3 parts of water. Used in preparing quick fixing baths.
• Ammonium bifluoride. Acid ammonium fluoride. HN₄F·HF
  White powder. Attacks the skin, poisonous. Easily soluble in water. Used for removing gelatine emulsion film from glass plates.
• Ammonium persulphate. (NH₄)₂S₂O₈
  Colorless crystals. Soluble 1 part in 1.7 parts of water. Used as a reducer.
• Ammonium thiocyanate. Ammonium sulphocyanide. NH₄CNS
  White deliquescent crystals. Very soluble in water. Used as a rapid fixing agent.
• Ammonium thiosulphate. Ammonium hysposulphate. (NH4)₂S2O₃
  White crystals, very soluble in water. Used as a rapid fixing agent.
• Benzotriazole. C₆H₅N₃
  White crystals. Very soluble in water. Antifoggant.
• Borax. Sodium biborate. Na₂B₄O₇·10H₂O
  White powder or crystals. Soluble 1 part in 17 parts water. Used as mild alkali in fine-grain developers.
• Boric acid. Boracic acid. H₃BO₃
  White lamellar crystals, greasy feel. Solubility 1:25 in water. Used as addition to fine grain developers.