A Quantitative Determination Of Iron Employing Gooch Crucibles

Abstract

Generally iron ores are analyzed for their iron content by dissolving accurately weighted samples in hydrochloric acid, oxidizing the iron to the ferric condition, and precipitating it with freshly distilled or filtered ammonium hydroxide solution. The resulting precipitate of ferric hydroxide is filtered through quantitative filter paper and washed free from chlorides with a dilute solution of ammonia. It is finally ignited and weighed as ferric oxide. During the ignition precautions are required that the oxide is not reduced by the burning paper. Since this ashing of the paper has to be watched and is time consuming, it was thought that it might be possible to use the Gooch crucible technique instead of the paper technique for iron. A search of chemical literature (Chemical Abstracts from 1925 to 1947 inclusive) failed to reveal any investigation wherein Gooch crucibles with an asbestos pad were used for iron analysis. However Popoff and Neuman (1) report good results in the analysis of sulfate as barium sulfate with Gooch crucibles. This determination is also one in which it has been the custom to use quantitative filter paper. In the method under investigation the preliminary steps pertaining to the precipitation and washing of the ferric hydroxide are identical to those of the filter paper analysis. Only in the final collection in the Gooch crucibles and ignition in a muffel furnace at approximately 700 C do the two analyses differ. For this reasons the precautions applying to one method would, for the most part, be observed in the other procedure.Generally iron ores are analyzed for their iron content by dissolving accurately weighted samples in hydrochloric acid, oxidizing the iron to the ferric condition, and precipitating it with freshly distilled or filtered ammonium hydroxide solution. The resulting precipitate of ferric hydroxide is filtered through quantitative filter paper and washed free from chlorides with a dilute solution of ammonia. It is finally ignited and weighed as ferric oxide. During the ignition precautions are required that the oxide is not reduced by the burning paper. Since this ashing of the paper has to be watched and is time consuming, it was thought that it might be possible to use the Gooch crucible technique instead of the paper technique for iron. A search of chemical literature (Chemical Abstracts from 1925 to 1947 inclusive) failed to reveal any investigation wherein Gooch crucibles with an asbestos pad were used for iron analysis. However Popoff and Neuman (1) report good results in the analysis of sulfate as barium sulfate with Gooch crucibles. This determination is also one in which it has been the custom to use quantitative filter paper. In the method under investigation the preliminary steps pertaining to the precipitation and washing of the ferric hydroxide are identical to those of the filter paper analysis. Only in the final collection in the Gooch crucibles and ignition in a muffel furnace at approximately 700 C do the two analyses differ. For this reasons the precautions applying to one method would, for the most part, be observed in the other procedure.