Conductometric titration with indicating resistance-III Mechanism of the PVC + Alassion CS (Cationite R-H) + dioctyl phthalate (plasticizer) membrane as indicating resistance.
The problem of conductometric acid-base titration in a highly-conducting medium (5M sodium chloride) has been solved by introducing a PVC + Alassion CS + dioctyl phthalate membrane between the two electrodes. The equivalence point is marked by a sudden decrease in conductivity. The membrane (obtained by plasticization at 175 degrees ) functions through the phthalic acid dissolved in the PVC membrane, this acid being formed by decomposition of the dioctyl phthalate by the sulphonic acid groups of the cation-exchanger. In this process the sulphonic acid groups are esterified, but hydrolyse on being treated for 2-3 hr with NaOH, and then increase the conductivity in the membrane.
Liteanu
C
C
Dept. of Analytical Chemistry and Dept. of Mineralogy University of Cluj, Cluj, Romania.
Ghergariu-Mîrza
L
L