Processing kodak motion picture films, module 3 analytical procedures

Determination of the pH of Processed Photographic Emulsions
ECP-2-806
INTRODUCTION
pH is a measure of the effective hydrogen ion concentration
in an aqueous solution. In this method, a sample of an
emulsion is cut into catalpa and is shaken with water. The pH
of the solution is then measured with a pair of electrodes and
a pH meter. The bulb of the glass electrode is entirely
immersed in the solution during measurement.
The method is not valid for lacquered emulsions because
most lacquers prevent the water from becoming equilibrated
with the surface of the emulsion. Any method employed for
removal of the lacquer may change the original pH value of
the emulsion.
RELIABILITY
It is expected that 95 percent of all individual pH
measurements on the name portion of processed emulsion
will be within the range of ± 0.08 pH unit.
SPECIAL APPARATUS
Corning Model 12 Research pH Meter or equivalent
Corning No. 476024 Glass Electrode or Leeds and
Northrup No, 117169 Glass Electrode
CORNING No. 476002, reference, ceramic junction,
calomel
Beaker, 30-mL
Test tube, 150 mm
New cork stoppers
REAGENTS
Use reagents that are ACS Reagent Grade unless specified
otherwise.
Potassium Acid Phthalate Buffer, 0.05 Molar
Borax Buffer, 0.01 Molar
Distilled Water, 27°C
PROCEDURE
Note: Measurements must be made in a well-ventilated
room where the atmosphere is free of volatile gases which
will form acids or bases in solution. Examples are chlorine,
hydrogen chloride, sulfur dioxide, and ammonia.
Preparation of the Meter and Electrodes
1. Follow the Standardization of pH Meter - High pH
Range procedure in Method ULM-191-2, pH
Measurement of Photographic Processing Solutions,
(or any subsequent pH method) for preparation of the
meter.
a. Adjust the temperature of the buffers and the
water.
b. Adjust the meter.
c. Standardize the meter with potassium acid
phthalate buffer.
d. Cross-check the electrodes with borax buffer.
2. Fasten the electrodes together as follows: Place a
rubber band around the electrodes so that they touch or
are very close together with the tips in a horizontal
plane. (The rubber band should be above the level of
any sample or buffer.)
Preparation of the Sample
Note: Be certain that the film sample is not contaminated in
any manner. Thin cloth gloves should be worn while
preparing the sample.
1. Cut the film as follows:
a. For 35 mm film samples, cut two 5-inch pieces
of film and carefully remove the perforations
from both sides. Cut the 5-inch pieces in half the
long way.
b. For 16 mm film samples, carefully remove the
perforations from one side of the film.
2. Arrange the pieces in a stack such that support sides
are face-to-face and emulsion sides are face-to-face.
Emulsion sides should face outward on each end of the
stack.
Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03 1