Estimation of contaminated iron in tungsten-cobalt alloy can be performed with the aid of paper-descending chromatographic method. After the alloy has been fused with sodium carbonate in a platinum crucible, tungsten is removed by precipitation. In the filtrate, iron and cobalt are separated by means of paper chromatography. Cut out the portion of paper strip which contains only iron and extract with 0.1 N hydrochloric acid. Finally iron is determined colorimetrically.