The encyclopaedia of photography : containing over one thousand references and illustrated with above 200 explanatory sketches and diagrams by the author / Walter E. Woodbury.

  • Woodbury, Walter E.
Date:
1890
Catalogue details

Licence: Public Domain Mark

Credit: The encyclopaedia of photography : containing over one thousand references and illustrated with above 200 explanatory sketches and diagrams by the author / Walter E. Woodbury. Source: Wellcome Collection.

    49/928 (page 45)
    when sensitised albumen paper is subjected to its fumes, and y this means increased sensitiveness and brilliancy are obtain . In development ammonia is used as the accelerator, an nossesses the advantage over all other alkalis of giving greater ErXicy and vigour. With some makes of plates, however, ammonia will produce green fog. In published formal* ammonia with specific gravity of -88o is generally recommended. It should however, be tested by the accompanying table, as it is difficult to obtain with so low a temperature of gravity. Table of Specific Gravity of Aqueous Ammonia at 6o° Fahr. Specific Gravity. 0-990 0980 0-970 0960 o'95° 0-940 o-g3o o geo ogio ogoo 0-980 o-88o Percentage of Ammonia. 2'3I 480 7'3i g-gi 1274 15-63 i8'64 2i-75 24-99 2833 31-75 ■3 c-(5n Ammonia Fuming.—See Fuming. Ammonio Nitrate Process (An emulsion process described under Emulsion).—In this the boiling of the emulsion is dispensed with, and is substituted by a method of keeping it at a moderate temperature in a state of strong alkalinity with ammonia. Ammonium Bichromate (Formula, (NH4)2 Cr2 07 ; molecular weight, 888-4).—Orange-coloured monochromic crystals, prepared by neutralising chromic acid with ammonia, and adding an equal part of chromic acid and evaporating. The crystals thus formed are soluble in water. Ammonium bichromate possesses the property of rendering certain organic bodies, such as albumen or gelatine, insoluble, when exposed to light. Potassium bichromate also possesses this property, and is usually preferred to ammonium bichromate in photo-mechanical printing. Ammonium Bromide (Formula, NH4Br ; molecular weight, 98) can be prepared by precipitating bromide of calcium by carbonate of ammonia, or by neutralising hydrobromic acid with ammonia. Ammonium bromide is formed in white crystals, very suluble in water, alcohol or ether. It is used in the manufac- ture of gelatino- or collodio-bromide emulsions, and as a restrainer in developing. Ammonium Carbonate (Formula, (NH4)2C03H.,0 ; mole- cular weight, 342).—Ammonium carbonate appears to exist in three forms, the normal, the acid, and the sesqui-carbonate. Commercial ammonium carbonate is made by sublimation from chalk and sal