Processing kodak motion picture films, module 3 analytical procedures

APPENDIX I
Spectrophotometer Calibration for Iron (II)
Determination
Note: Use this appendix to recheck the spectrophotometer
linear calibration for iron (II) at least every 6 months. Also
use it the first time this method is performed, and whenever
the spectrophotometer has been adjusted or repaired.
Preparation of Standard
Prepare a litre of fresh Process ECN-2 “UL” bleach solution
containing all the constituents of the mix at the aim tank
concentrations.
1. For the four iron (II) standards in “UL” bleach, weigh
out 0.088, 0.176, 0.355, and 0.710 g portions of
assayed ferrous ammonium sulfate, 6-hydrate, record
to the nearest 0.1 mg. See Module 4, Reagent
Preparation Procedures, for the assay procedure for
ferrous ammonium sulfate, 6-hydrate.
2. Quantitatively transfer each of the four weighings of
ferrous ammonium sulfate to four 50-mL volumetric
flasks, labeled with the corresponding weights. Rinse
each weighing boat into the corresponding flask with
the fresh “UL” bleach mix. Swirl each flask to dissolve
the ferrous ammonium sulfate.
Note: The iron (II) material (ferrous ammonium
sulfate) takes some time to dissolve.
3. When the ferrous ammonium sulfate has dissolved, fill
each volumetric flask to the mark with the fresh “UL”
bleach mix. Invert each flask 6-10 times to thoroughly
mix the solutions.
4. Run each sample in (at least) duplicate by the method
described in the preceding PROCEDURE, p. -3.
Determination of Iron (II)
The calculation to determine the amount of iron (II) in the
standards from the weighed amount of ferrous ammonium
sulfate is as follows:
g/L iron (II) =
g/Liron(II) =
Where:
gofFe(NH4) 2(SO4) 2 6H2O x 55.85 x 1000 mL wt/wt assay
x
(50 mL) 391.85 1 L 100
gofFe(NH4 ) 2 (SO4 ) 2 6H2O = weight recorded in Step 1
55.85 = atomic weight of Iron
1000 mL = factor to convert mL to L
50 mL =
volume of the ferrous
ammonium sulfate standard
392.13 =
molecular weight of ferrous
ammonium sulfate, 6-hydrate
100 = correction for wt/wt% to wt/wt
wt/wt assay =
assay of Fe(NH 4 ) 2 (SO 4 ) 2
based on determination in
Appendix II
Regression
The data collected from above was used to construct the
regression equation for the calibration line.
The reliability of the resulting calibration line was
determined in the following manner on a spectrophotometer
in a Kodak laboratory. Four fresh “UL” bleach solutions
were prepared containing 0.2503, 0.4995, 1.006, and
2.013 g/L iron (II). Each solution was analyzed in duplicate
to create a linear regression (based on 12 data points) for
each spectrophotometer being used. The average standard
deviation (1s) for the linear regression was 0.011 g/L iron
(II), corresponding to a 95 percent confidence estimate of
± 0.02 g/L. Each laboratory should calibrate their
spectrophotometer; otherwise, an unknown bias may exist.
Ferrous Ammonium
Sulfate, g/L
0.0882
0.0882
0.0882
0.1760
0.1760
0.1760
0.3545
0.3545
0.3545
0.7091
0.7091
0.7091
g/L Iron (II)
0.2503
0.2503
0.2503
0.4995
0.4995
0.4995
1.0062
1.0062
1.0062
2.0126
2.0126
2.0126
Absorbance of
Sample
The data was then processed by a least squares linear
regression to develop the line, y = mx + b. Definition of the
equation is found in the Calculations section (page -3).
The equation generated using the above data was:
Iron (II), g/L = 2.57(A spl ) + 0.046
4 Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03
0.081
0.081
0.083
0.174
0.174
0.175
0.376
0.374
0.372
0.766
0.763
0.769