Copper(II) Sulfate as a New Indicator Substitute to Phenolphthalein in Neutralization Titrimetry

Abstract

Copper(II) sulfate pentahydrate has been standardized as an

advantageous indicator substitute to phenolphthalein in neutralization

titrimetry. Copper sulfate 1000 μg mL^-1 titrand (ca. 2x 10^-3 M

near equivalence point) and pheolophthalein 10  μg mL^-1 titrand

were compared as indicators for standardization of alkali hydroxides

and mineral acids' over the normality range 0.03 N to 1 N. The

end-point with copper sulfate was shatp, and marked by appearance

of a bluish-white turbidity, due to formation of cupric hydroxide

near equivalence point, that did not disappear on shaking and standing.

The mean normality values obtained with compared indicators

did not differ significantly (p> 0.1). Copper sulfate offers certain

advantages over phenolphthalein: it is water-soluble, the end-point

is highly stable, and it may be used to measure titratable acidity of

coloured solutions.