Processing kodak motion picture films, module 3 analytical procedures

PROCEDURE A
Rapid Determination of the Approximate Silver
Concentration in Thiosulfate Fixing Baths
Note: Use the markings on the cylinders for all
measurement.
Treatment of Sample
1. Obtain three 100-mL glass-stoppered graduated
cylinders (labeled 2, 4, and 6). Add to each graduated
cylinder 10 mL of fixing bath sample, 10 mL of 0.1 M
potassium ferricyanide, and 10 mL of 6 N accelerator
reagent. Swirl to mix. If the resulting color is:
a. Reddish-brown, proceed to Step 2.
b. Black, add 10 ml more of 0.1 M potassium
ferricyanide and swirl to mix. Proceed to Step 2
if the resulting color is reddish-brown. If not,
start over again, using a fresh sample and a
0.2 M potassium ferricyanide reagent.
2. Using a polyethylene squeeze bottle, add to the
cylinders the following volumes of 0.00926 N
thioacetamide:
Cylinder
mL 0.0926 N Thioacetamide
Identification
2 20
4 40
6 60
3. Stopper and shake all cylinders vigorously for
5 seconds.
4. Filter approximately 20 ml of the contents of each
cylinder through a Whatman No. 3 (12.5 cm diameter)
filter paper and collect the filtrates in beakers
containing approximately 5 mL of 0.00926 N
thioacetamide.
5. Observe the appearance of the beakers’ contents and
refer to Table 1, Decision Sheet for Determining Silver
Concentration Range (10 mL Sample) Procedure A.
Reporting Results
1. The results from these three cylinders permit the
conclusion that the silver content of the fix is:
a. less than 2 g/L
b. between 2 and 4 g/L
c. between 4 and 6 g/L
d. over 6 g/L *
2. One more individual trial will suffice to establish the
silver content between two silver concentrations
1.0 g/L apart (See PROCEDURE B).
* If the silver content is more than 6 g/L, dilute the sample with an equal
volume of water and rerun the determinations corresponding to cylinders 2,
4, and 6. Remember to multiply any final answer by 2.
Table 1 Decision Sheet for Determining Silver
Concentration Range (10 mL Sample) Procedure A
Cylinder
No.
0.00926 N
Thioacetamide
Added
If the
Contents of
the Beaker
Turns Color, *
Amount of
Silver in Fix is
More Than
1 10 1.0 g/L
2 20 2.0 g/L
3 30 3.0 g/L
4 40 4.0 g/L
5 50 5.0 g/L
6 60 6.0 g/L
If the
Contents of
the Beaker
Remains
Clear, †
Amount of
Silver in Fix is
Less Than
* The color in the beaker is greater than a blank consisting of appropriate
amounts of sample, potassium ferricyanide, 6 N NaOH-EDTA reagent
and water (in place of 0.00926 N thioacetamide) which have been
filtered, the filtrate being collected in about 5 mL of water.
† The color in the beaker is not greater than a blank prepared as above.
PROCEDURE B
Determination of Silver in Thiosulfate Fixing Baths
Note: Procedure A has established the approximate silver
concentration. If it is desirable to determine the
concentration more precisely, it is necessary to “zero-in” on
the end point by measuring volumes with pipets and burets
and by using smaller increments of 0.00926 N thioacetamide
in the end point region. This procedure establishes the silver
content between two concentrations 0.1 g/L apart, with three
or fewer trials.
Treatment of Sample
1. Pipet into 4 100-ml glass-stoppered graduated
cylinders 10.0 mL of fixing bath. Using the markings
on the cylinders, add to one of the cylinders 10 mL of
0.1 potassium ferricyanide, and 10 mL of 6 N
accelerator reagent. Swirl to mix. If the resulting color
is:
a. reddish-brown, proceed to Step 2.
b. black, add 10 mL more of 0.1 N potassium
ferricyanide. Swirl to mix. Proceed to Step 2 if
the resulting color is reddish-brown. If not, start
over again using a fresh sample and a 0.2 M
potassium ferricyanide reagent. Prepare the
remaining cylinders similarly.
2. Add from a buret the appropriate amount of 0.00926 N
thioacetamide to each cylinder.
2 Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03