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396 Transactions of S.M.P.E., Yol. XIII, Xo. 38, 1929
(a) The melting point of the fixed-out film should range from 120° to 160° F.
(b) If the sulfurization life of the bath is one and one-half days at 115° F. the bath will keep satisfactorily for about three weeks at 70° F. which is ample for most purposes.
(c) The developer capacity should be such that at least 3% of MQ25 developer can be added before a precipitate of aluminium sulfite is formed. This capacity is considered adequate especially if the bath is revived at intervals with acid.
On reference to Fig. 4 it is seen that the following formula possesses the above properties and in practice this formula has been found to be entirely satisfactory^
Fixing Bath (Formula F-2)
Metric Avoirdupois
Hypo 240 grams 100 lbs.
"Water to make 1 liter 50 gallons
Add to 50 c.c. per liter or 2^ gallons per 50 gallons of the following Stock Hardener:
* The concentration of hypo to be used may be varied to satisfy individual requirements.
Stock Hardening Solution (Formula F-2a)
Metric Avoirdupois
Sodium sulfite (desiccated) Acetic acid (glacial)*-^ Powdered potassium almn Water to make
*" Use 314 times the quantity if 28% acetic acid is used.
The hardening solution should be prepared separately and added to the cooled hypo solution as required. To prepare the hardener, dissolve the sulfite and alum separately, add the acid to the sulfite solution, and then add the alum solution, adding water to make the required volume. Do not add the sulfite to the alum solution before adding the acid or a precipitate will form.^^
When the hardener is stored a white incrustation of basic aluminium acetate tends to precipitate out on the walls of the container but this does not impair the hardening properties of the solution. During storage in an open crock it is important to use a floating cover consisting of a sheet of No. 1 Kodaloid in order to prevent loss of sulfur dioxide and oxidation of the sulfite by the
60 grams
100 c.c. 120 grams
25 lbs.
5 gallons 50 lbs.
1 liter
50 gallons