8Processing KODAK Motion Picture Films, Module 3, Analytical Procedures • H24.03

CALCULATIONS

For Potentiometric Titration

A. Hypo Index (HI) or Total Reductants:

Where:

B. Thiosulfate (S2O3

=

):

Where:

C. Sodium Sulfite (Na2SO3):

Where:
HI (1), mL = (mL Blank A – mL Sample A) (N Na2S2O3)
0.1000 N Na2S2O3
HI (1), mL = mL of 0.1000 N I2 consumed by 1.0mL
sample
mL Blank A = millilitres of titrant at the end point of the
blank titration of potentiometric Procedure A.
mL Sample A = millilitres of titrant at the end point of the
sample titration of potentiometric
Procedure A.
N Na2S2O3= normality of the titrant (meq/mL)
0.1000 = nominal value for the normality of the titrant,
in meq/mL
g/L S2O3
=
=(mL Blank B – mL Sample B)(N Na2S2O3)(112.13)(1000)
sample size (1000)
mL Blank B = millilitres of titrant at the end point of the
blank titration of potentiometric Procedure B
mL Sample B = millilitres of titrant at the end point of the
sample titration of potentiometric
Procedure B.
N Na2S2O3= normality of the titrant (meq/mL)
112.13 = equivalent weight of thiosulfate expressed in
mg/meq
1000 = conversion factor of milligrams to grams
1000 = conversion factor of millilitres to litres
sample size = sample size used in potentiometr ic
Procedure B (2.0 mL)
mL Blank A – mL Sample A = D mL A
mL Blank B – mL Sample B = D mL B
g/L Na2SO3=[(D mL A)(2.0) – (D mL B)](N Na2S2O3)(63.02)(1000)
sample size (1000)
N Na2S2O3= normality of the titrant
2.0 = conversion of hypo index to 2.0 mL sample
size
63.02 = equivalent weight of sodium sulfite in mg/
meq
1000 = conversion factor of milligrams to grams
sample size = sample size used in potentiometr ic
Procedure B (2.0 mL)
1000 = conversion factor of millilitres to litres