Processing kodak motion picture films, module 3 analytical procedures

Determination of the pH of the Eastman Color Print-2 Stop Bath
ECP-2-890
Process ECN-2 ECP-2D VNF-1/LC RVNP
Formulas — SB-14 — —
INTRODUCTION
Exposure of the electrodes to the low pH of the stop bath
causes improper electrode response when the same
electrodes are used to measure the pH of more alkaline
solutions. A separate set of electrodes should be used for
measurement of stop bath pH.
Sulfuric acid, 0.25 N, (pH 0.95 ± 0.05) is used as a
reference solution in measuring stop bath pH. The electrodes
and meter are first standardized with potassium acid
phthalate buffer (pH 4.010 at 27°C). The pH of the 0.25 N
sulfuric acid is then measured. If the pH value for the 0.25 N
sulfuric acid is 0.95 ± 0.05, the meter is adjusted to the
nominal value of 0.95 and the pH of the stop bath is
measured. Stop bath pH is measured at 27 ± 5°C.
SPECIAL APPARATUS
Corning Model 12 Research pH Meter or equivalent
Corning No. 476024 Glass Electrode or Leeds and
Northrup No, 117169 Glass Electrode
Beckman Fiber Junction Calomel Electrode, No. 39170
(filled with 3.5 N potassium chloride)
REAGENTS
Use reagents that are ACS Reagent Grade unless specified
otherwise.
Potassium Acid Phthalate Buffer, 0.05 M
Sulfuric Acid, 0.25 N
PROCEDURE
1. Follow the Standardization of pH Meter - Low pH
Range procedure in Method ULM-191-2, pH
Measurement of Photographic Processing Solutions,
(or any subsequent pH method) for preparation of the
meter.
2. Rinse the electrode assembly with distilled water and
immerse the electrodes in potassium acid phthalate
buffer. Set a timer for two minutes. At the end of the
two minutes standardize the meter at pH 4.010.
3. Rinse the electrode assembly with distilled water and
lower the electrodes into 0.25 N sulfuric acid solution
in a 150-mL beaker. Set a timer for two minutes. At the
end of two minutes the pH should be 0.95 ± 0.05.
a. If the pH of the 0.25 N sulfuric acid is
0.95 ± 0.05, adjust the meter to the nominal
value of 0.95 and proceed to step 4.
b. If the pH is not 0.95, repeat the procedure using
another glass electrode.
4. Rinse the electrodes and lower the assembly into the
stop bath solution. Set a timer for two minutes. At the
end of two minutes record the pH of the stop bath. If
another stop bath pH measurement is to be made,
repeat the procedure.
Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03 1