Processing kodak motion picture films, module 3 analytical procedures

Titrimetric Determination of Buffer Capacity of Accelerator Solution
ECN-2-755
ECR-755A
Process ECN-2 ECP-2D VNF-1/LC RVNP
Formulas SR-31 — AB-3 AB-3
INTRODUCTION
Each process accelerator solution is buffered to a different
pH. Buffer curves indicate that the optimum pH range for
measuring buffering capacity is between pH 3.50 and
pH 6.00. The buffer capacity is measured in terms of the
volume of base required to change the pH from 3.5 to 6.0,
and is expressed in terms of glacial acetic acid, mL/L, or
sodium acetate, g/L.
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.
RELIABILITY
Process ECN-2—Four standard mixes were prepared
containing 0.0, 10.0, 20.0, and 30.0 mL/L glacial acetic acid.
They were analyzed in duplicate by three analysts in one
laboratory The 95 percent confidence limits for a single
determination are ± 0.20 mL/L glacial acetic acid.
Process VNF-1/RVNP—Four standard mixes were
prepared containing 0.0, 6.89, 10.34, and 13.79 mL/L glacial
acetic acid. They were analyzed in duplicate by three
analysts in two laboratories. The 95 percent confidence
limits for a single determination are ± 0.07 mL/L glacial
acetic acid.
SPECIAL APPARATUS
pH Meter
Reference Electrode, Ceramic Junction, Calomel,
Corning No. 476002, Beckman No. 38423 or equivalent
(Filled with 3.5 M potassium chloride solution)
Indicator Electrode, glass (pH), Rugged Bulb, Corning
No. 476024 or equivalent
25 and 50-mL Burets
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.
1 N Sodium Hydroxide, NaOH
(standardized to 4 decimal places)
1.0 N Sulfuric Acid, H 2SO 4
PROCEDURE
Meter Preparation
1. Follow Method ULM-191-2, pH Measurement of
Photographic Processing Solutions, to prepare the pH
meter for making measurements below pH 9.
Titration
1. Pipet (wipe the pipet before leveling) the sample size
below into a beaker containing a magnetic stirrer.
Process Beaker Size Sample Size
ECN-2, AB-2 200 mL 50.0 mL
VNF-1/RVNP, AB-3 400 mL 100.0 mL
2. Immerse the electrode assembly in the sample solution
and start stirring.
3. Using 1.0 N sulfuric acid, adjust the pH of the sample
to pH 3.5 (this volume does not have to be measured).
4. Using the buret size indicated below, titrate the sample
to pH 6.00 with standardized 1 N sodium hydroxide.
Record the volume of titrant used.
Process Buret
ECN-2, AB-2 50 mL
VNF-1/RVNP, AB-3 25 mL
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. Place the electrode
assembly in pH 4.01 potassium acid phthalate buffer
for storage.
Calculations
ECN-2, AB-2
Buffer Capacity, mL/L =
1.22(N NaOH)(mL NaOH) – 0.52
VNF-1/RVNP, AB-3
Buffer Capacity, mL/L =
0.65(N NaOH)(mL NaOH) – 1.79
Buffer Capacity, g/L * =
0.94(N NaOH)(mL NaOH) – 2.6
* As sodium acetate.
Note: One gram of sodium acetate is equivalent to 0.689 mL
of glacial acetic acid.
Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03 1