Processing kodak motion picture films, module 3 analytical procedures

Potentiometric Determination of Ferrocyanide in Ferricyanide Bleach and Ferrocyanide
Stock Solutions
ECR-1102C
Process ECN-2 ECP-2D VNF-1/LC RVNP
Formulas — — SR-40 —
PRINCIPLE
Ferrocyanide is oxidized in an acid solution by sulfato
cerate. This reaction is:
Ce +4 + Fe(CN) 6 -4 → Ce +3 + Fe(CN) 6 -3
The sample is titrated potentiometrically. The progress of
the titration is followed by measuring the potential of a
platinum electrode against a double junction reference
electrode. Results are reported in terms of sodium
ferrocyanide decahydrate.
The record or plotted curve will “break” in a direction
opposite that found in a bromide titration.
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
This method is based on stoichiometry. The 95 percent
confidence limits for a single determination are expected to
be ± 3 percent.
SPECIAL APPARATUS
Automatic Titrator or pH Meter
Reference Electrode, Double Junction, Orion No. 900200
or equivalent
Indicator Electrode, Platinum Inlay/Disc, Beckman No.
39273 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.
7.0 N Sulfuric Acid, H 2 SO 4
0.05 N Sulfato Cerate (standardized to 4 decimal places)
PROCEDURE
Sample Treatment
1. Pipet (wipe the pipet before leveling) the sample of
ferricyanide bleach into a beaker according to the
following table.
Concentration of
Ferrocyanide
(g/L)
2. Add distilled water from a graduated cylinder
according to the table above.
3. Add 7.0 N sulfuric acid from a tip-up pipet according
to the table above. Mix thoroughly.
Potentiometric Titration
1. Titrate the solution with standardized 0.05 N sulfato
cerate, using an automatic titrator of pH meter. See
Potentiometric Titrations for Photoprocessing
Solutions, Method ULM-0003-01, or any subsequent
revision.
Calculation
Sample
Size
(mL)
Sample
(mL)
Distilled
Water
(mL)
Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03 1
7.0 N
Acid
(mL)
Below 5 600 200.0 100 50
Between 5 and 10 600 100.0 200 50
Between 10 and 20 400 50.0 200 50
Between 20 and 40 400 25.0 200 50
Between 40 and 80 400 10.0 200 50
Between 80 and 200 400 5.00 200 50
Over 200 400 2.00 200 50
Na 4 Fe(CN) 6 H 2 O, g/L =
(N cerate)(mL cerate)(eq wt Na 4 Fe(CN) 6 10H 2 O)(1000) =
(mL sample)(1000)
(N cerate)(mL cerate)(484.1)(1000)
(mL sample)(1000)
484.1(N cerate)(mL cerate)
(mL sample)
=
=