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1949 SPRAY PROCESSING 679
an average (for fine-grain positive), taken on the basis of his estimates, would be 10 grams. The reduction of this quantity of silver would require about 5 grams of hydroquinone. Any of the systems studied in this work would process nearly 1000 feet of motion picture positive film per hour, so the minimum average rate of loss of hydroquinone would be 5 grams per hour. However, experience has shown that most systems require at least 5 liters of bromide-free replenisher per 1000 feet in order to keep the soluble bromide concentration of the bath down to a reasonable level of about 2 grams of potassium bromide per liter. This quantity of replenisher is sufficient to replace the carry-over of developer and to occasion some overflow, or "bleed." Thus in practice, excluding loss by aerial oxidation, each of the five systems might be expected to cost (in grams of hydroquinone) :
Concentration in
Developer, Cost (in Grams of HydroGrams per Liter quinone) per 5 Liters
Elon 1.72 5 X 2 X 1.72 = 17. 2 grams
Hydroquinone 3.30 5 X 3.30 = 16.5 grams
plus
Cost of developing the image = 5 grams
Total = 38. 7 grams
or in round numbers, about 40 grams of developing agent in terms of hydroquinone equivalents, when processing positives. For negatives the figure would be somewhat greater:
5 [(2 X 2.0) + 5.0] + 2.5 = 47.5
or in round numbers, 50 grams of developing agent in terms of hydroquinone equivalents if it is assumed that the average weight of image silver per 1000 feet of negative film is half of that found on prints.
Some loss of developing agent is occasioned by adsorption in the film even if unexposed film is processed and no development occurs.9 No special allowance for this loss is made here in view of the approximate nature of the calculation and the enhancement of the values in the rounding-off.
If these figures of 40 and 50 grams hydroquinone equivalents per hour are compared with the autoxidation figures in Fig. 8, it will be seen that in most cases the appropriate autoxidation loss is less than half of them. Only the L-R Spray system shows autoxidation losses which are equal to, or greater than, the development loss figure.