Processing kodak motion picture films, module 3 analytical procedures

Titrimetric Determination of Total Alkalinity of a Processing Solution
ECR-702J
Process ECN-2 ECP-2D VNF-1/LC RVNP
Formulas — —
DR-100/101
DR-150/151
DR-105
DR-150
INTRODUCTION
A critical appraisal of the pH, specific gravity, and total
alkalinity of a developer mix is useful in detecting incorrect
amounts of the inorganic constituents and certain of the
organic constituents.
PRINCIPLE
The total alkalinity (T. Alk.) of a processing solution is
defined as the millilitres of standardized 0.1 N sulfuric acid
required to adjust a specified volume of processing solution
to pH 4.3. That pH was selected because most salts derived
from weak acids show an inflection point in their titration
curves near pH 4.3.
Samples that are colored (and some colorless samples)
when titrated visually do not give a clear end point, thus
causing excessive variability. For this reason, potentiometric
titrations are recommended. Complete titration curves need
not be plotted routinely.
A pH meter can be used with glass and calomel electrodes.
The instrument is standardized at the nominal temperature at
which pH measurements are obtained. The temperature is
usually 25°C (77°F).
Table 2, Contribution of Constituents to Total Alkalinity
of a Typical Replenisher Solution, shows the contribution of
each constituent to the total alkalinity of two developers. The
T. Alk. of the negative developer is mainly a measure of the
sodium carbonate content. The T. Alk. of the print
developers is primarily a measure of the carbonate but also
indicates a significant contribution from the sulfite.
The sample size is so chosen that the total volume of
sulfuric acid consumed falls between 25 and 45 mL. The
sample sizes must be specified with all total alkalinity
analyses.
This method requires handling potentially hazardous
chemicals. Consult the Material Safety Data Sheet for each
chemical before use. MSDS's are available from your
chemical supplier.
SPECIAL APPARATUS
pH Meter or Automatic Titrator
Calomel reference electrode filled with 3.5 N KCl,
CORNING Model 476002, or equivalent
pH Indicator electrode, CORNING Model 476024, or
equivalent
Note: Use pipets and volumetric glassware meeting the
“Class A” definition by the National Institute of Standards
and Technology (NIST)
REAGENTS
Use ACS Reagent Grade reagents unless specified
otherwise.
0.1 N Sulfuric Acid, H 2SO 4
(standardized to four decimal places)
PROCEDURE
Preparation of the Meter
Follow Method ULM-191-2, pH Measurement of
Photographic Processing Solutions (or any subsequent pH
method), for making pH measurements below pH 9
Titration of the Sample and Reporting Results
1. Pipet the sample volume indicated below into a
150-mL beaker containing 50 mL of distilled water.
The water should be approximately the same
temperature as the buffer used in the cross-check
Process Formula Sample Size
VNF-1/LC
DR-100/101
DR-150/151
4.00 mL
10.0 mL
2. Place the electrode assembly and stirrer in the solution,
turn on the stirrer.
3. Titrate to a pH of 4.3 with standardized 0.1 N sulfuric
acid, allowing the needle of the pH scale to equilibrate
as the acid is slowly added. When the region of pH 5
is reached, add the titrant in 0.l0-mL increments,
allowing the needle in the pH meter to equilibrate after
each addition.
4. Report the mL of acid required to reach a pH of 4.3.
Note: This is, by definition, the total alkalinity.
Always indicate the sample size when reporting the
results.
5. Remove the sample and rinse the electrode assembly
with distilled water. If rinsing does not completely
remove sample deposits, wipe the assembly with a
cleansing tissue and rerinse. Replace in pH 4.01
potassium acid phthalate buffer.
Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03 1
RVNP
DR-105
DR-150
4.00 mL
10.0 mL