Abstract: In the production of phenacetin from p-chloronitrobenzene was often found a trace of coloured organic impurities in the product. In the residue of watery solution of the crude product of phenacetin the writer found five spots by paper chromatograph. Two of them directly affected the quality of the product. One was found p-dichloroazobenzene and the other "phenetidine red". Some improvements on the technological processes were made to avoid the formation of impurities. The quality of phenacetin was improved markedly.