A New Assay for Copper(II) Sulfate by Acidometry and Its Comparison with Iodometric Assay

Abstract

An acidimetric assay for copper(II) sulfate has been developed and
compared with iodometric assay. The assay is based on complete precipitanon
of copper(II) as cupric hydroxide in presence of dilute sodium
hydroxide solution; reconstituting the purified precipitate in slight excess
of standard H₂SO₄, determining the amount of cupric hydroxide by backtitration
of the solution against standard sodium hydroxide solution,
wherein copper(II) ions act as self-indicator, and the end-point is characterized
by appearance of a faint bluish-white turbidity that does not disappear
on shaking and standing. Each mL of ¹N H₂SO₄ consumed is
equivalent to ¹mL of ¹N Cu(OH)₂ that is equivalent to 31.77 mg of
copper(II), or 124.85 mg of copper(II) sulfate pentahydrate. The assay is
comparable to iodometric assay with no significant difference between
mean percent purity values (P> 0.1), and precisions of two sets of data
(P> 0.1). Acidimetric assay offers certain advantages over iodometric
assay. It is simpler to perform, obviates the use of external indicator, and
involves lesser number of chemicals and variables. The technique can be
employed for determining percent purity of commercially produced copper
(II) sulfate or other copper salts following their conversion to copper
sulfate.