Adding sodium hydroxide (NaOH) and hydrated copper(II) sulfate to urine in a test tube is a test for proteins in urine.
This test depends on the ability of sodium hydroxide (NaOH) and hydrated copper(II) sulfate to form purple-coloured cordination complexes with peptides. The appearance of this purple colour is a positive test for protiens in urine.
Hence, when a few drops of a mixture of sodium hydroxide and copper(ii) tetraoxosulphate (vi) solution added to a sample of urine test in a test tube, the solution may turn purple indicating the presence of proteins in urine or remain colourless indicating the absence of proteins in urine.
