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8 Processing KODAK Motion Picture Films, Module 3, Analytical Procedures • H24.03
CALCULATIONS
For Potentiometric Titration
A. Hypo Index (HI) or Total Reductants:
Where:
B. Thiosulfate (S
2
O
3
=
):
Where:
C. Sodium Sulfite (Na
2
SO
3
):
Where:
HI (1), mL =
(mL Blank A – mL Sample A) (N Na
2
S
2
O
3
)
0.1000 N Na
2
S
2
O
3
HI (1), mL = mL of 0.1000 N I
2
consumed by 1.0 mL
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 Na
2
S
2
O
3
= normality of the titrant (meq/mL)
0.1000 = nominal value for the normality of the titrant,
in meq/mL
g/L S
2
O
3
=
=
(mL Blank B – mL Sample B)(N Na
2
S
2
O
3
)(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 Na
2
S
2
O
3
= 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 potentiometric
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 Na
2
SO
3
=
[(D mL A)(2.0) – (D mL B)](N Na
2
S
2
O
3
)(63.02)(1000)
sample size (1000)
N Na
2
S
2
O
3
= 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 potentiometric
Procedure B (2.0 mL)
1000 = conversion factor of millilitres to litres