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.
A METHOD OF TESTING FOR THE PRESENCE OF SODIUM THIOSULFATE IN MOTION PICTURE FILMS*
J. I. CRABTREE AND J. F. ROSS
It is necessary that photographic films be thoroughly washed after fixing; otherwise, if any appreciable quantity of sodium thiosulfate or other sulfur-containing compounds remain in the film, sooner or later they react with the silver image to form silver sulfide with the result that the image becomes brown, and it is said to have faded.
Three common methods are used to detect the presence of sodium thiosulfate in photographic materials and roughly determine the thoroughness of washing:
(1) When the film is thought to be washed, it is lifted from the washing tray or tank and the surface water allowed to drain into 10 or 20 cc. of the following alkaline potassium permanganate solution:
Metric Avoirdupois
Potassium permanganate 0 . 5 gram 7 . 5 grains
Sodium hydroxide (caustic soda) 1.0 gram 15.0 grains
Water (distilled) to make 1.0 liter 32 .0 ounces
For use take stock solution 1 part, water 20 parts. If a small percentage of hypo is present, the violet color will turn orange in about 30 seconds, and with larger concentrations of hypo the orange color will change to yellow.
Oxidizable organic matter, if present in the water, reacts with the permanganate solution and changes the color in the same manner as hypo. The water should, therefore, be tested as follows:
Add a quantity of water equal in volume to that of the wash water drained from the film to a second test solution prepared as above from pure water. If the sample to which tap water has been added remains a violet color, this indicates the absence of organic matter and it will be unnecessary to repeat the test. If the color is changed slightly by the tap water, the presence of hypo in the film will be shown by the relative color change of the two samples. For
* Communication No. 412 from the Kodak Research Laboratories.
419