Processing kodak motion picture films, module 3 analytical procedures

Potentiometric Determination of Ferrocyanide in Process ECP Ferricyanide Bleach and
Ferrocyanide Stock Solutions
ECP-0023/01
INTRODUCTION
Ferrocyanide is determined by an oxidation titration with
standardized sulfato cerate in an acid solution. The reaction
is:
Ce +4 + Fe(CN) 6 4- → Ce +3 + Fe(CN) 6 3-
The endpoint of the titration is detected
potentiometrically. The electrodes used for the titration are a
platinum indicator electrode and a double junction reference
electrode. Results are reported in terms of potassium
ferrocyanide trihydrate, K 4 Fe(CN) 6 3H 2 O.
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.
Sample
Mean
(g/L K 4 Fe(CN) 6 3H 2 O) N
PRECISION AND BIAS
Repeatability Standard Deviation, 1sr and 95
Percent Confidence Estimate (not including Bias)
Repeatability standard deviation is an estimate of the
variability one trained analyst should be able to obtain under
favorable conditions (analyzing a sample, with one
instrument, within one day).
The 95 percent confidence estimate (calculated using the
repeatability standard deviation) around a single test result
will include the mean value 95 percent of the time.
To obtain the repeatability data, a single skilled analyst
performed three (3) replicates on each of the following
solutions during methods development.
1. A “fresh” ferricyanide bleach prepared with all
components at their respective “working tank” aim
concentrations.
2. The same “fresh” solution as in number 1, above,
reanalyzed after making an analytically weighed,
standard addition of 2.9990 g/L K4Fe(CN) 6 3H2O. 3. A “seasoned” ferricyanide bleach analyzed
potentiometrically as received, at 3.0645 g/L
K4Fe(CN) 6 3H2O. 4. The same “seasoned” solution as in number 3, above,
reanalyzed after making an analytically weighed,
standard addition of 1.0034 g/L K4Fe(CN) 6 3H2O. K 4 Fe(CN) 6 3H 2 O
Repeatability Standard
Deviation, 1s r
(g/L K 4 Fe(CN) 6 3H 2 O)
95 Percent Confidence
Estimate
g/L K 4 Fe(CN) 6 3H 2 O)
“Fresh”
“Fresh” plus
0.097 3 0.0081 ± 0.035
Standard
Addition
“Seasoned”,
3.075 3 0.0024 ± 0.010
As
Received
“Seasoned”
3.064 3 0.0142 ± 0.061
plus
Standard
Addition
4.040 3 0.0063 ± 0.027
Processing KODAK Motion Picture Films, Module 3, Analytical Procedures H24.03 7