Processing kodak motion picture films, module 3 analytical procedures

PROCEDURE
Sample Treatment
1. Pipet, wipe the pipet before leveling, 50.0 mL of
standardized 0.1 N potassium iodate into a 250-mL
Erlenmeyer flask.
2. Add 25 mL of 7.0 N sulfuric acid from a tip-up pipet.
3. Add 25 mL of 0.60 M potassium iodide from a tip-up
pipet.
4. Pipet (wipe) 25.0 mL of sample into the flask.
Titration
1. Titrate with standardized 0.1 N sodium thiosulfate to a
light yellow color. Then, add 5 mL of starch indicator
from a tip-up pipet and continue the titration until the
blue color disappears.
2. Analyze for RA-1 using Method ECR-0001-1 (or
subsequent revision).
Calculations
1. Calculate the apparent total sulfite concentration using
the following equation:
Apparent Total Na 2 SO 3 , g/L =
[(N KIO 3 )(mL KIO 3 ) – (N Na 2 S 2 O 3 )(mL Na 2 S 2 O 3 )](eq wt Na 2 SO 3 )(1000) =
(mL sample)(1000)
[(N KIO 3 )(50.0) – (N Na 2 S 2 O 3 )(mL Na 2 S 2 O 3 )](63.02)(1000) =
(1.00)(1000)
2.521[(N KIO 3)(50.0) – (N Na 2S 2O 3)(mL Na 2S 2O 3)]
2. Correct the apparent sulfite concentration for RA-1
using the following equation:
Total Na 2SO 3, g/L =
(Apparent Na 2 SO 3 , g/L) – [0.0034 (RA-1, mg/L) – 0.001)]
2 Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03