GB307716A - Improvements in the preparation of photosensitive photographic emulsions - Google Patents

Abstract

307,716. Johnson, J. Y., (I. G. Farbenindustrie Akt.-Ges.). Nov. 7, 1927. Emulsion coatings.-The sensitiveness of emulsions containing water-insoluble mercuric oxalate or its complex ammine compounds is increased by generating in or adding thereto, or to the ingredients employed for the preparation thereof, a sensitizing agent such as an inorganic sensitizing metal salt, for example a salt of one of the heavy metals, mercury, silver, thallium, gold, or platinum, and/or an organic sensitizing dyestuff, for example eosine or erythrosine. Tannin or a similar toning agent may be added to the emulsion, or the prints produced may be toned like silver prints, for example with uranium nitrate. A printing-out emulsion is produced by including, for example 1 to 3 per cent of mercuric iodide, and the emulsion may further be bathed before or after coating in a 1 per cent silver nitrate solution. A developing emulsion is produced for example by including 0.5 to 2 per cent of mercuric iodide and 0.05-0.2 per cent of silver iodide, development being effected with metol hydroquinone the action of which is arrested bv immersion in a bath containing acetic acid and potassium metabisulphite, and fixing being performed with alkaline thiosulphate. Examples are described of the preparation of various emulsions employing gelatin as vehicle, including an emulsion which prints out feebly and is developed to full intensity.