This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
NH3 + H2O.
The aqueous solution of ammonia gas is a clear, colorless liquid, the specific gravity of which decreases as the ammonia content increases. For analytical purposes two solutions of different concentrations are ordinarily used, of which one has a specific gravity of about 0.96, and contains about 10% of NH3, while the other, the concentrated, has a specific gravity of about 0.925, and contains about 20% of NH3. In American laboratories a still more concentrated solution of ammonia is employed. Its strength is about 28%, and it is generally designated as stronger ammonia water. The 20% ammonia water is termed concentrated ammonia water.
(NH4)2 Cr2O7 - V. Ammonium Dichromate. Orange-colored crystals. Soluble in water. Used sometimes in place of potassium bichromate for sensitizing carbon tissue. Is more sensitive to light than potassium bichromate.
NH4Br - II.
(NH4) HCO3 (NH4) NH2CO2. Sal Volatile, or Smelling Salts. The term ammonium carbonate is generally applied to a mixture of ammonium bicarbonate and carbonate. White, crystalline, translucent masses which readily effloresce, become opaque, and give off an odor of ammonia; sharp, saline taste. Soluble in 5 parts water; partly soluble in alcohol. May be used in developers, but not so suitable as ammonia. Can be used instead of ammonia for fuming albumen paper.
NH4Cl - II.
(See Ammonium Bichromate.)
NH4I - II.
White to yellowish-white, crystalline powder; odorless; sharp, saline taste; unstable. Soluble in 0.6 parts water, and 9 parts alcohol. Used in preparing sensitized collodion.
Colorless crystals; usually long, thin, rhombic prisms; deliquescent; odorless; sharp, bitter taste. Soluble in 0.5 parts water, 20 parts alcohol. Used, with the addition of water, to keep solutions cool in hot weather, the dish containing them being placed in a larger one filled with moistened ammonium nitrate.
(NH4)2 C2O4 + H2O.
Colorless crystals. Soluble in 25 parts water. Used in some formulae for sensitizing platinum paper.
(NH4)2S2O8 - II, 277; VIII.
Colorless crystals resembling ordinary table salt. Soluble in water. Used as a reducer for hard, chalky negatives, as it acts on the dense portions to a greater extent than on the shadow or thin portions.