Processing kodak motion picture films, module 3 analytical procedures

PROCEDURE B – VISUAL TITRATION
Reliability
No statistical calibration was performed on this method at
the time it was written. Procedure B is reproduced here from
previous Methods ECN-2-1305A, ECP-2-1305B, and
ECR-1305L for those without access to the preferred
auto-titration method.
Apparatus
All volumetric glassware should meet all “Class A”
specifications, as defined by American Society for Testing
and Materials (ASTM) Standards E 287, E 288, and E 969,
unless otherwise stated.
20.0-, 25.0-, and 50.0-mL pipets
250-mL conical flask
50.0-mL buret
Reagents
All chemicals are ACS Reagent Grade unless otherwise
stated.
0.1 N Potassium Iodate, KIO 3
0.6 M Potassium Iodide, KI
0.1 N Sodium Thiosulfate, Na 2 S 2 O 3 , standardized to
4 places
7 N Sulfuric Acid, H 2SO 4
Starch Indicator
Calculations
Na2SO3,g/L = [(mL B x 1.25) – mL A] x (N Na2S2O3 ) x (eq. wt.) x (1000)
(ml sample) x (1000)
ECN-2
Na2SO3 ,g/L = [(mL B x 1.25) – mL A] x (N Na2S2O3) x (63.02) x (1000)
(50) x (1000)
ECP-2D
Na2SO3 ,g/L = [(mL B x 1.25) – mL A] x (N Na2S2O3 ) x (63.02) x (1000)
(25) x (1000)
VNF-1/RVNP
Na2SO3,g/L = [(mL B x 1.25) – mL A] x (N Na2S2O3 ) x (63.02) x (1000)
(5) x (1000)
Where:
mL A = mL of Na2S2O3 consumed by sample
mL B = mL of Na2S2O3 consumed by blank
1.25 =
mL of 0.1 N potassium iodate used for sample
mL of 0.1 N potassium iodate used for blank
Procedure
Treatment and Titration of the Sample
1. Pipet 50.0 mL of 0.1 N potassium iodate into a 250-mL
conical flask containing a TEFLON-coated stirring bar
2. While stirring, add 25 mL of 7.0 N sulfuric acid and
25 mL of 0.60 M potassium iodide
3. While stirring, immediately pipet the sample size
indicated below into the flask near the surface of the
liquid. Rinse the sides of the flask with reagent water.
Process Sample Size
ECN-2 50.0 mL
ECP-2D 25.0 mL
VNF-1/LC 5.00 mL
RVNP 5.00 mL
4. While stirring, immediately titrate with standardized
0.1 N sodium thiosulfate solution (50-mL buret) to a
light yellow color. Add 5 mL of starch indicator and
titrate, drop by drop, until the disappearance of the
blue color for at least 15 seconds. Record this volume
as mL A.
5. Repeat Steps 1 through 4 using 40.0 mL (pipet two
20.0-mL portions) of standardized 0.1 N potassium
iodate instead of 50.0 mL, and substituting distilled
water for the sample. This is the blank. Record this
volume as mL B.
4 Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03