Colorimetric determination of chromium in aluminium alloys by diphenylcarbazide method

A concise method for the determination of chromium in aluminium alloys colorimetrically by the use of diphenylcarbazide is described. The method is based on measurement of the violet colour formed between chromate III ion (Cr3+) and diphenylcarbazide. The diphenylcarbazide forms a violet complex which absorbs at 540 nm. Other interfering metal ions including manganese and iron were masked by making alkaline with sodium hydroxide (NaOH). Potassium heptaoxodichromate (VI) K2Cr2O7 solution (283ppm) was used as standard. Three aliquots (2ml, 5ml and 10ml) of standards were used for measurement. The solutions of samples were made in aquaregia and colour reagent added. Absorbance of standard as well as samples was measured at 540 nm using a colorimeter. A working curve obtained from known concentrations of standard was used to calculate the concentration of chromium in each sample. The findings show that colorimetric determination of chromium by diphenylcarbazide method is a simple, effective and valuable alternative method for the determination of chromium in aluminium alloys.