
14 Advanced Process Control and Simulation for Chemical Engineers
2.8 DIPHENYLCARBAZIDE METHOD
Diphenylcarbazide (sym-diphenylcarbazide, diphenylcarbohydrazide) reacts in acid
medium with Cu (II) ions to give a violet solution which is the basis of this sensitive
method.
Many investigators have studied the reaction [8], offering rather divergent expla-
nations of its mechanism. Pfl aum and Howick [9], among others [12, 15, 16], have
shown that the cationic (II) and diphenylcarbazone fails to yield a violet color. In all
probability, the reaction involves unhydrated chromium (III) ions formed during the
oxidation of diphenylcarbazide to diphenylcarbazone. ...