Processing kodak motion picture films, module 3 analytical procedures

Iodometric Determination of Formalin in Stabilizer
ECR-1803G
Process ECN-2 ECP-2D VNF-1/LC RVNP
Formulas – S-1c S-16 S-16
INTRODUCTION
In this method the sample is added to an excess of
hypoiodite, formed by acidifying standard potassium iodate,
adding an excess of potassium iodide, and making the
solution alkaline. Part of the hypoiodite is reduced by the
formaldehyde in the sample, and the unreduced part is
converted to iodine by acidifying the solution. The iodine is
then titrated with sodium thiosulfate using starch indicator.
KODAK Stabilizer Additive does not interfere in these
reactions.
Formalin is a solution of formaldehyde in water. The
formulas for processing solutions are based on formalin
which is 37.5 percent formaldehyde by weight and with a
specific gravity of 1.095. The percent by weight and the
specific gravity enter into the calculations for this
determination. The specific gravity varies slightly depending
on the concentration of methyl alcohol present as an
antifreeze and preservative.
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.
Note: Use pipets and volumetric glassware meeting the
“Class A” definition by the National Institute of Standards
and Technology (NIST).
RELIABILITY
The equation for determining the formalin content should be
checked by preparing several standard laboratory mixes
containing the particular strength of the formalin stock
solution used in the processing solution. Normally the results
obtained are slightly below the amount added to the mix.
The results obtained on standard mixes should be within
5 percent of the mix value. If this is not the case, the
concentration and the specific gravity of the formalin stock
solution must be determined. The concentration can be
found by using the ANSI test procedure, ANSI
PH4.152-198O(R1987).
REAGENTS
Use ACS Reagent Grade reagents unless specified
otherwise.
0.1 N Potassium Iodate, KIO 3
(standardized to 4 decimal places)
7.0 N Sulfuric Acid, H 2 SO 4
0.60 M Potassium Iodide, KI
2.5 N Sodium Hydroxide, NaOH
0.1 N Sodium Thiosulfate, Na 2 S 2 O 3
(standardized to 4 decimal places)
Starch Indicator
PROCEDURE
Sample Treatment
1. Pipet (wipe the pipet before leveling) 50.0 mL of
standardized 0.1 N potassium iodate into a 250-mL
glass-stoppered conical flask.
2. Add 5 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. Swirl to mix.
4. Pipet (wipe the pipet before leveling) the indicated
volume of stabilizer into the flask:
Process Formula Sample Size
ECP-2D S-1c 10.00 mL
VNF-1/LC S-16 20.0 mL
RVNP S-16 20.0 mL
5. Add 25 mL of 2.5 N sodium hydroxide from a tip-up
pipet.
6. Stopper the flask, swirl the contents, and allow it to
stand approximately one minute.
7. At the end of one minute, add 10 mL of 7.0 N sulfuric
acid from a tip-up pipet.
Titration
1. Titrate immediately with standardized 0.1 N sodium
thiosulfate to a light yellow color.
2. Add 5 mL of starch indicator from a tip-up pipet and
continue the titration to the disappearance of the blue
color.
3. Record the mL of standardized 0.1 sodium thiosulfate
used.
Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03 1