Processing kodak motion picture films, module 3 analytical procedures

Potentiometric Determination of Kodak Persulfate Bleach Accelerator PBA-1 in
Accelerator Solution
ECN-2-2100B
ECR-2100B
Process ECN-2 ECP-2D VNF-1/LC RVNP
Formulas SR-31 — SR-45 SR-45
INTRODUCTION
Strong base is added to the sample to hydrolyze the KODAK
Persulfate bleach accelerator PBA-1 to a titratable
mercaptan. The PBA-1 content is measured by means of a
potentiometric titration with silver nitrate titrant using a
silver/sulfide electrode as an indicator and a double junction
electrode as a reference. This analysis is performed using an
automatic titrator.
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
Fresh Process ECN-2, ECP-2D and VNF-1/RVNP bleach
accelerator samples were analyzed by three analysts in two
laboratories. A linear regression of the data generated the
standard deviation (s), and 95 percent confidence estimates
(CE) given below. No bias from stoichiometry was found.
Process ECN-2 ECP-2D VNF/RVNP
Sample Range, g/L 2–8 1–8 1–7
Sample No. 3 4 4
Data pts. 18 24 24
(s), g/L ± 0.05 ± 0.04 ± 0.02
95% CE, g/L ± 0.10 ± 0.10 ± 0.10
A seasoned sample from processes ECN-2 and ECP-2D
was analyzed five times by each of three analysts over two
days. The 95 percent confidence estimate was ± 0.04 g/L
PBA-1 (s = ± 0.02 g/L) for both Process ECN-2 and
ECP-2D. No statistically significant day-to-day or analystto-analyst
variability was found.
A standard addition of 0.5 g/L PBA-1 was made to two
seasoned samples from processes ECN-2 and ECP-2D. Each
sample was analyzed in duplicate by three analysts. Based on
the 12 data points for each process, the method found
97 percent for ECN-2 and 100 percent for ECP-2D.
SPECIAL APPARATUS
Automatic Titrator (with a 20-mL buret)
Orion Double Junction Reference Electrode,
Cat. No. 900200 or equivalent
Orion Silver/Silver Sulfide Indicator Electrode,
Cat. No. 941600 or equivalent
Note: Do not use a silver billet or bar electrode as prepared
by the obsolete method 900 “Procedure For Electroplating A
Silver-Silver Iodide Electrode.”
Note: Use pipets and volumetric glassware meeting the
“Class A” definition by the National Institute of Standards
and Technology (NIST).
REAGENTS
Use reagents that are ACS Reagent Grade unless specified
otherwise.
10 N Sodium Hydroxide, NaOH
0.05 N Silver Nitrate, AgNO 3
(standardized to 4 decimal places)
PROCEDURE
Preparation of the Sample
1. Pipet 50.0 mL of sample into a 400-mL beaker
equipped with a magnetic stirring bar.
Warning
Sodium hydroxide is caustic. Avoid contact with skin
and eyes. In case of contact, flush with water.
2. Using a tip-up pipet, add 10 mL of 10 N sodium
hydroxide to the beaker containing the sample.
3. Place the beaker on a magnetic stirrer and set a timer
for 3 minutes.
4. After the solution has stirred for 3 minutes, add
250 mL of distilled water from a graduated cylinder.
Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03 1