We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
July, 1943] REMOVAL OF HYPO AND SILVER SALTS 25
sodium thiosulfate in the Kodak F-5, F-23, and F-24 solutions and these baths compared with the regular formulas. The addition of ammonium thiosulfate to the baths increased the pH somewhat so that an adjustment to the pH of the regular baths was necessary.
With substitution in the F-5 bath, washing tests indicated that after fixing in the 7.? per cent ammonium thiosulfate bath the rate of removal of hypo was equal to that with the regular bath but, after fixing in the 14.4 per cent bath, the rate was approximately 30 per cent greater. No differences were measurable between sodium and ammonium thiosulfate in the case of the chrome alum (F-23) or non-hardening (F-24) fixing baths. With respect to silver, any differences were so small that they were not detectable by the sulfide test.
EFFECT OF VARIOUS FACTORS
(/) Time of Fixation. — Tests were made with developed Eastman Motion Picture SuperJO" Panchromatic Negative Film, Type 1232, and Eastman Motion Picture Release Positive Film, Type 1301, in both fresh and exhausted sulfitebisulfite (F-24), potassium alumboric acid (F-5) and chrome alum (F-23) fixing baths. The baths were exhausted to 125, 250, 375, and 500 feet per gallon with (a) the £H maintained at the pH of the fresh bath, and (b) the £H increased by carry-over of developer. The times of fixing used were 2, 4, 6, and 10 times the apparent "time to clear" in each bath. All test strips were washed for 15 minutes.
The "time to clear" of an emulsion is a somewhat variable factor and dependent upon (a) the nature and intensity of the incident light used to observe the clearing point (by refraction), and (b) the ability of the individual to judge the clearing point. It is particularly difficult to determine in the case of exhausted fixing baths because of the very low rate of conversion of the halides to soluble complexes. For these reasons the term "apparent time to clear" was preferred.
The most satisfactory method of viewing was to direct a beam of tungsten light between the film and a black background at an angle of approximately 45 degrees to the background. The most accurate "time to clear" determination required uniform agitation such that the conversion of the halides was uniform over the entire emulsion area. Relative clearing and fixing times should be determined at a fixed temperature, for example, 68°F.