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Notes on the preparation of standard cellulose. II
IO8
F~ASTMAN KODAK COMPANY NOTES.
[J.F.I.
shift smaller than 1.38 would definitely contradict the relativity theory, and would be compatible with an aether theory. The experiment is of interest as a possible crucial test. T h e results o f the actual measurements, which are accurate to - o . o I of a fringe-width, should be available before the end o f the year. NOTES ON THE PREPARATION OF STANDARD CELLULOSE. II.~ By A. B. Corey and H. LeB. Gray.
IN A previous paper it was noted that the standard cellulose, prepared by the tentative method described, gave too high an ash. It has been found that if the resulting cellulose, before drying, is treated with I per cent. acetic acid solution for two hours at room temperature and then washed with four changes of distilled water, the ash content is reduced to a very low quantity without any apparent injurious effect on the cellulose. In several samples the ash was reduced f r o m o.12 to 0.0 4 per cent. by this treatment. The writers have observed, during the alkali boiling of different cottons, that with some a longer time is necessary to discharge the yellow color of the solution than with others. Results on one sample of cotton show that the percentage of a-cellulose may be slightly increased by boiling with the I per cent. sodium h y d r o x i d e solution for ten hours instead of six. It seems advisable to allow the displacing alkali solution to enter a little more rapidly so that twelve litres are used during the time of boiling; and also to continue the heating and displacement with I per cent. alkali for one hour after the yellow color has entirely disappeared. THE
PHOTOGRAPHIC
REPRODUCTION
OF
TONE.'
(THE HURTER AND DRIFFIELD MEMORIAL LECTURE.) By C. E. K. Mees.
NATURAL objects are seen as a series of tones differing in brightness, these differences being due to differences either in illumination or in reflecting power. T h e range of contrast varies f r o m 1 : 2 to i : i : I O O , most subjects falling between contrasts Communication No. 216 from the Research Laboratories of the Eastman Kodak Company and published in Ind. Enu. Chem., I6: II3o, 1924. " Communication No. 224 from the Research Laboratories of the Eastman Kodak Company and published in Phot. J., 64: 311, 1924.
F~ASTMAN KODAK COMPANY NOTES.
[J.F.I.
shift smaller than 1.38 would definitely contradict the relativity theory, and would be compatible with an aether theory. The experiment is of interest as a possible crucial test. T h e results o f the actual measurements, which are accurate to - o . o I of a fringe-width, should be available before the end o f the year. NOTES ON THE PREPARATION OF STANDARD CELLULOSE. II.~ By A. B. Corey and H. LeB. Gray.
IN A previous paper it was noted that the standard cellulose, prepared by the tentative method described, gave too high an ash. It has been found that if the resulting cellulose, before drying, is treated with I per cent. acetic acid solution for two hours at room temperature and then washed with four changes of distilled water, the ash content is reduced to a very low quantity without any apparent injurious effect on the cellulose. In several samples the ash was reduced f r o m o.12 to 0.0 4 per cent. by this treatment. The writers have observed, during the alkali boiling of different cottons, that with some a longer time is necessary to discharge the yellow color of the solution than with others. Results on one sample of cotton show that the percentage of a-cellulose may be slightly increased by boiling with the I per cent. sodium h y d r o x i d e solution for ten hours instead of six. It seems advisable to allow the displacing alkali solution to enter a little more rapidly so that twelve litres are used during the time of boiling; and also to continue the heating and displacement with I per cent. alkali for one hour after the yellow color has entirely disappeared. THE
PHOTOGRAPHIC
REPRODUCTION
OF
TONE.'
(THE HURTER AND DRIFFIELD MEMORIAL LECTURE.) By C. E. K. Mees.
NATURAL objects are seen as a series of tones differing in brightness, these differences being due to differences either in illumination or in reflecting power. T h e range of contrast varies f r o m 1 : 2 to i : i : I O O , most subjects falling between contrasts Communication No. 216 from the Research Laboratories of the Eastman Kodak Company and published in Ind. Enu. Chem., I6: II3o, 1924. " Communication No. 224 from the Research Laboratories of the Eastman Kodak Company and published in Phot. J., 64: 311, 1924.