Bismuth ............... 7 parts.
Lead.................. 4 M .
Tin.................. 2 ..
Cadmium ...... ...... ... 1 part.
Gall. See Ox-Gall.
Gallate of Iron Process. See Ink Process.
Gallic Acid (Ger., Gallussdure; Fr., Acide gallique; Ital., Acido gallicd). HQH505 = 170. Obtained by fermentation from powdered galls. Solubility 1 per cent, in cold, 33 per cent, in boiling water, very soluble in alcohol, less so in ether. It was used for developing in the collodion and waxed paper processes, and has been also suggested for developing gelatino-chloride paper.
Gallon. A gallon of water weighs 10 lbs. at normal tempera-ture. See Weighing and Measuring.
Galvanography, Photo-. A general term for processes in which a printing plate or block is produced by electrotyping on a photographic original; the earliest forms of the method being the electrotyping of the daguerreotype image, the resulting plate, however, being too shallow for satisfactory printing. According to Waterhouse's method a carbon print is developed on a metal plate (see Carbon Printing), and dusted over while wet with waxed sand. When dry the sand is brushed off, and we then have a basis upon which the electrotype cast is made. Accord-ing to the Pretsch method, a gelatine film very similar in its nature to the collotype film is the basis upon which the electro-type copper is deposited. Details of photo-galvanographic methods belong rather to special treatises than a general handbook, and the reader is referred to Herr Volkmer's Photogalvanographie (German), published by Wilhelm Knapp, of Halle-a-S. English readers will find details of the Pretsch method in the Process Photogram for January 1897. The follow-ing articles in this Dictionary have a direct or indirect bearing on galvanographic methods: - Photogravure, Fish Glue Process, Daguerreotypes (etching of), Obernetter's Process, Elec-trotyping, Types (originating by Photography).
Gamboge, or Camboge (Ger., Gummigutli; Fr., Gomme Gutte; Ital., Gomma Guttd). An orange-coloured gum resin, from the