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.