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676 J. I. CRABTREE AND H. D. RUSSELL [J. S. M. p. E.
Formula II
Hypo 300 grams 125 Ibs.
Sodium sulfite (desiccated) 17.5 grams 7 Ibs. 5 oz.
Potassium chrome alum 32.0 grams 13 Ibs. 4 oz.
Sulfuric acid (concentrated) 2 cc. 123/4 oz.
Water to make 1 liter 50 gals.
It is not desirable to prepare a stock hardener consisting of the sulfite, alum, and sulfuric acid because this would lose its hardening properties on keeping.
Practical exhaustion tests were made with the above formulas to determine their behavior on exhaustion with motion picture film developed in the D-16 and D-76 developers, the processing being conducted both at 70°F. and 85°F.
(1) Effect of Addition of Developer on Hardening Properties. — Since the loss of hardening properties of a chrome alum fixing bath with immediate use is a result of the addition of developer, increasing quantities of D-16* and D-76** developers were added to definite quantities of fixing bath No. I stored in bottles at 70°F. and 110°F., and the hardening properties of these solutions determined at daily intervals as follows:
Strips of Eastman motion picture positive film were developed for five minutes in D-16 developer, then placed directly in the fixing
* Formula
D-16
Metric
Avoirdupois
Elon
0.3 gram
2 oz.
Sodium sulfite (desiccated)
40.0 grams
16V2 Ibs.
Hydroquinone
6.0 grams
2Va Ibs.
Sodium carbonate (desiccated)
19 . 0 grams
73/4 Ibs.
Potassium bromide
0 . 9 gram
53/4 OZ.
Citric acid
0 . 7 gram
4V« oz.
Potassium metabisulfite
1 . 5 grams
10 oz.
Water to make
1.0 liter
50 gals.
Average time of development: 5 to 10 minutes at 65 °K. (18 °C.) ** Formula D-76
Metric Avoirdupois
Elon 2 grams 13 oz.
Sodium sulfite (desiccated) 100 grams 42 Ibs.
Hydroquinone 5 grams 2 Ibs.
Borax 2 grams 13 oz.
Water to make 1 liter 50 gals.
Average time of development: 12 to 25 minutes at 65 °F. (18 °C.)