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A contribution to the preparation of standard gelatin
NOTES FROM THE RESEARCH LABORATORY, EASTMAN KODAK COMPANY.* A CONTRIBUTION TO THE PREPARATION OF STANDARD GELATIN. 1 J. H. Hudson and S. E. Sheppard.
I'r is recommended t h a t the first standard gelatin prepared should be for scientific purposes ; that is, it should be as near as possible a definite chemical compound, with physical properties equal to, or better than, the highest grade gelatin now obtainable. T h e question of its suitability for photographic or other industrial uses should not enter the question of its merits, as standards for a special purpose material can be prepared later. Preferably the standard gelatin should be prepared from well-limed calfskin, and only the first extract taken. The finished product should contain not more t h a n o.o5 per cent. ash and be at its isoelectric point of pH 4.7. More definite specifications for a standard gelatin should be decided upon only after several laboratories have completely tested a purified gelatin. DYE TONING W I T H SINGLE SOLUTIONSY J. I. Crabtree and C. E. Des.
PREVIOUS experimenters employed single solution dye toning baths consisting essentially of a mixture of the mordanting bath and a basic dye, together with a protective agent; b u t since the basic dye invariably precipitated on standing, none of these formulas has been satisfactory. A bath has been devised which contains no heavy metal * Communicated by the Director. 1 Communication No. 364 front the Kodak Research I.aboratories and published in Ind. Eng. Chem. 2I: 263 . 1929. 2 Communication No. 372 from the Kodak Research Laboratories and published in Amer. Phot. 22: 656. t928; Trans. Soc. Mot. Pict. Eng. 12: No. 36; Brit. J. Phot. 75:768. I928' 699
I'r is recommended t h a t the first standard gelatin prepared should be for scientific purposes ; that is, it should be as near as possible a definite chemical compound, with physical properties equal to, or better than, the highest grade gelatin now obtainable. T h e question of its suitability for photographic or other industrial uses should not enter the question of its merits, as standards for a special purpose material can be prepared later. Preferably the standard gelatin should be prepared from well-limed calfskin, and only the first extract taken. The finished product should contain not more t h a n o.o5 per cent. ash and be at its isoelectric point of pH 4.7. More definite specifications for a standard gelatin should be decided upon only after several laboratories have completely tested a purified gelatin. DYE TONING W I T H SINGLE SOLUTIONSY J. I. Crabtree and C. E. Des.
PREVIOUS experimenters employed single solution dye toning baths consisting essentially of a mixture of the mordanting bath and a basic dye, together with a protective agent; b u t since the basic dye invariably precipitated on standing, none of these formulas has been satisfactory. A bath has been devised which contains no heavy metal * Communicated by the Director. 1 Communication No. 364 front the Kodak Research I.aboratories and published in Ind. Eng. Chem. 2I: 263 . 1929. 2 Communication No. 372 from the Kodak Research Laboratories and published in Amer. Phot. 22: 656. t928; Trans. Soc. Mot. Pict. Eng. 12: No. 36; Brit. J. Phot. 75:768. I928' 699