Hach-Lange TITRALAB 840_845 Reference Manual - Manual (Page 209)

Titra Lab ® TitraLab 840 and 845 Reference Manual
Page 209
4. Back titration
The back titration is performed in two steps:
- reaction of the excess reagent with the sample : z sample + w Excess
- reaction of the titrant with the excess of reagent : x Excess + y titrant
According to the definition of stoichiometric coefficients, z is equal to y.
The calculation is performed in equivalent. If the concentrations are not in equivalent per litre,
then the stoichiometric coefficients are used. When the titration starts, the excess reagent has
a number of equivalent equal to : Ve * Ce * c' , with:
The reaction of the excess reagent with the titrant gives : Vtit * Ctit * c'', with:
Then, the sample concentration is calculated as follows:
With:
Ce c’ value
eq/l 1
meq/l 0.001
mol/l z
mmol/l 0.001 * z
Ctit c’’ value
eq/l 1
meq/l 0.001
mol/l x
mmol/l 0.001 * x
“C
smp
” “c” if “Vs” in “ml”
eq/l = N 1
meq/l 1000
mol/l = M 1 / w
mmol/l 1000 / w
g/l = mg/ml M
smp
/ w
mg/l M
smp
* 1000 / w
mol Vs * 0.001 / w
mmol Vs / w
g M
smp
* Vs * 0.001 / w
mg M
smp
* Vs / w
µg M
smp
* Vs * 1000 / w
Csmp
V e Ce c ′ Vtit Ctit c″ Ч Ч – Ч Ч
Vs
-------------------------------------------------------------------- c
Ч
=