For Visual Titration
A. Hypo Index (HI) or Total Reductants:
(mL Blank A – mL Sample A) (N Na2S2O3)
HI (1), mL =
0.1000 N Na2S2O3
Where:
HI (1), mL = mL of 0.1000 N I2 consumed by 1.0 mL sample
mL Blank A = millilitres of titrant at the end point of the blank visual titration, Procedure A.
mL Sample A = millilitres of titrant at the end point of the sample visual titration, Procedure A.
N Na2S2O3 = normality of the titrant (meq/mL)
0.1000 = nominal value for the normality of the titrant, in meq/mL
B. Thiosulfate (S2O3=):
(mL I2)(N I2)[eq. wt. S2O3=](1000)
g/L S2O3= =
(mL Sample size)(1000)
Where:
mL I2 = millilitres of iodine titrant measured at the visual end point
N I2 = normality of the titrant (meq/mL)
[eq. wt. S2O3=] = equivalent weight of thiosulfate expressed in mg/meq (112.13)
1000 = factors to convert mg/mL to g/L
C. Sodium Sulfite (Na2SO3):
[(HI)(N* I2)(3)] – [(mL I2)(N I2)](eq. wt. S2O3=)(1000)
g/L Na2SO3 =
(mL Sample size)(1000)
Where:
HI = mL of 0.1000 N I2 consumed by 1.0 mL sample
N* I2 = nominal 0.1000 normality of iodine used in the Hypo Index calculation (meq/mL)
3= conversion of Hypo Index to a 3.0 mL sample size
mL I2 = millilitres of iodine titrant measured at the visual end point, Procedure B
N I2 = normality of the iodine titrant (meq/mL) used in Procedure B, visual end point
eq. wt. S2O3= = equivalent weight of thiosulfate expressed in mg/meq (112.13)
mL Sample = sample size used in Procedure B, visual end point
1000 = conversion factors for milligrams to grams and milliliters to liters
10 | Processing KODAK Motion Picture Films, Module 3, Analytical Procedures • H24.03 |