Processing kodak motion picture films, module 3 analytical procedures

Spectrophotometric Determination of Ferrocyanide in Effluents
1122B
INTRODUCTION
The sample is diluted, if necessary, such that the
ferrocyanide [Fe(CN) 6 –4] concentration falls within a range
of 0.5 to 5 mg/L. A dilution of 25 mL of sample to 250 mL
is sufficient for samples of as high as 100 mg/L sodium
ferrocyanide [Na 4 Fe(CN) 6 10 H 2 O] concentration. In most
cases, this is adequate. However, this method can be used for
samples of sodium ferrocyanide concentrations as high as
one g/L by making a second dilution of 25 mL to 250 mL.
After the dilution, the sample is made alkaline to dissolve
ferrocyanide. The sample is then filtered to remove any
insolubles. The filtrate is acidified and ferrous/ferric reagent
added. After 15 minutes, the intensity of the blue color
produced is measured at 700 nm using a spectrophotometer
equipped with a tungsten lamp.
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.
RELIABILITY
This method was calibrated by preparing fixes containing
known concentrations of sodium ferrocyanide,
Na 4Fe(CN) 6 10 H 2O.
SPECIAL APPARATUS
Spectrophotometer with a tungsten lamp
1-cm Silica Cell
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.
2.5 N Sodium Hydroxide, NaOH
Concentrated Hydrochloric Acid, HCl
Ferrous/Ferric Reagent
PROCEDURE
1. Pipet (wipe the pipet before leveling) 25.0 mL of
effluent sample (Solution A) into a 250-mL volumetric
flask. Dilute to volume with distilled water; stopper
and invert the flask several times to mix. (This is
Solution B.)
2. Add, from a graduated cylinder, 100 mL of the diluted
sample (Solution B) from Step 1 to a 250-mL conical
flask, and make it alkaline by adding 10 drops of 2.5 N
sodium hydroxide.
3. Mix thoroughly and filter the solution through
Whatman 2V filter paper.
4. Make the filtrate acid by the dropwise addition of
concentrated hydrochloric acid. (Use litmus paper as
an indicator.)
5. Pipet (wipe) 40.0 mL of the filtrate into each of two
150-mL beakers. (One portion is read as a blank.)
6. For samples do:
a. Add 2 drops of ferrous/ferric reagent; allow the
beaker to stand for 15 minutes.
b. If a blue color is apparent, rinse and fill a 1-cm
silica cell with solution from the beaker.
Measure the absorbance of the sample vs. air at
700 nm on a spectrophotometer equipped with a
tungsten lamp.
c. Record this reading as A700 sample.
Note: If no blue color is produced by Solution B
in Step 6a, repeat Steps 2 through 8 using the
undiluted effluent sample (Solution A).
7. For blanks do:
a. Allow the beaker to stand for 15 minutes.
b. Measure the absorbance of the blank at 700 nm.
c. Record this reading as A700 blank.
Note: If the absorbance of Solution B at 700 nm
after Step 7a is greater than 0.800, dilute again
25 mL of Solution B to 250 mL and repeat Steps
2 through 8 with this Solution (C).
Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03 1