Processing kodak motion picture films, module 3 analytical procedures

Potentiometric Determination of Bromide in Reversal Color Developers
ECR-930E
Process ECN-2 ECP-2D VNF-1/LC RVNP
Formulas — — DR-150/151 * DR-150
* This procedure was developed for a process other than VNF-1 and
RVNP, that did not contain sodium thiocyanate. Thiocyanate is a well
known interferent to halide determinations when using a silver ion
titration, due to co-precipitation. A significant high bias may be found
when applying this procedure to determine bromide in developers
containing thiocyanate.
INTRODUCTION
This method contains two separate procedures for analysis of
bromide. Procedure A is used for the analysis of fresh tank
and replenisher solutions. Procedure B is used for the
analysis of seasoned tank solutions. Analysis of seasoned
tank solutions using Procedure A will result in erroneously
high results—as much as 0.3 g/L This effect is dependent
upon seasoning; aging is not a factor. Acetone is added in
Procedure A to eliminate interference.
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.
Procedure A—The sample is acidified and acetone added.
It is then titrated potentiometrically with silver nitrate.
Procedure B—Bromide enrichment by selective
precipitation is utilized. All of the bromide is precipitated as
silver bromide along with minor amounts of other silver
salts, by the addition of a small excess of silver to an
acidified sample of seasoned developer. The silver salts are
filtered and developed by a silver-halide developer, releasing
soluble bromide. The sample is filtered again, the filtrate is
acidified, and then the treated sample is titrated
potentiometrically with silver nitrate.
As an aid in selecting the proper inflection point and
detecting instrument trouble or analytical errors, a set of
standard titration curves of all developers should be kept on
file. Such curves can be compared with the general shape and
relative position of any routine titration curve. Figure 1
includes typical titration curves as an aid in determining the
increment size to use in the region of the end point and the
expected potential change in millivolts.
RELIABILITY
Procedure A—The 95 percent confidence limits for an
individual analysis of a fresh tank sample are estimated to be
slightly less than ± 0.05 g/L sodium bromide.
Procedure B—This procedure was specifically designed
for current mix formulations and variance due to seasoning.
Any change in mix formulation, especially in bromide
concentration, may necessitate recalibration.
Four seasoned samples in the appropriate bromide
concentration range were analyzed by three analysts. Based
on the 12 data points obtained, the 95 percent confidence
limits for an individual determination are ± 0.05 g/L sodium
bromide.
SPECIAL APPARATUS
Reference Electrode, Double Junction, Orion No.900200
or equivalent
Indicator Electrode, Silver Billet, Beckman No. 39261 or
equivalent
Millipore Filter apparatus (Millipore Corp., Bedford,
Mass. 01730, Catalog No. XX1004700)
Millipore Filter membrane (0.45 micron porosity 47 mm,
Catalog No. HAWP-04700
Exhaust Hood
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.
Acetone, (CH 3 ) 2 CO
1.0 M Ammonium Nitrate, NH 4 NO 3
Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03 1
Celite
Silver Halide Developer
0.05 N Silver Nitrate, AgNO 3 (standardized to 4 decimal
places)
18 N Sulfuric Acid, H 2SO 4