T. Yoshinaga et al., Polyvinyl alcohol as a useful indicator on iodometry: Volumetric and spectrophotometric studies on iodine-PVA and iodine-starch complexes, ANAL SCI, 17(2), 2001, pp. 333-337
Iodometry is one of the easiest, most rapid and accurate methods for the de
termination of a relatively small amount of oxidizing agent, such as residu
al chlorine. Starch has long been used as a useful color indicator in iodom
etry. However, we found that PVA (polyvinyl alcohol with partially saponifi
cated; e.g., saponification degree of 88%) is a more useful color indicator
than starch. For example, at 20 degreesC, the PVA indicator gave similar p
rofiles of iodine concentration vs. titration efficiencies (percent recover
ies) to those of starch at 0 degreesC. At 0 degreesC, the PVA indicator det
ected 1.1 mg I-2/L (11 mug It: with 10 mt sample volume) with a high percen
tage of recovery (= 95%). Furthermore, at 20 degreesC an iodine concentrati
on of 0.36 mg/L (which corresponds to a residual chlorine concentration of
0.1 mg CI2/L) could be detected using PVA color indicator assuming an appro
priate correction.