Estimation of metals as sulphides : Estimation of platinum metals

1. It has been shown that all the platinum metals with the exception of osmium can be estimated as sulphide if the solution containing the metal is treated with a large excess of alkali sulphide followed by excess of acetic acid and ammonium acetate. The precipitate of the sulphide can be washed with water, alcohol and ether successively, dried in a vacuum desiccator, and weighed. 2. By the above procedure it is possible to complete the analysis for all the platinum metals within 3 hours, whereas the procedures described in the literature require much longer time —in many cases more than 24 hours. 3. The precipitates obtained by the older procedures were very sticky and difficult to filter. By carrying out the precipitation in the presence of acetic acid and ammonium acetate it has been possible to obtain the precipitate in an easily filterable form. 4. The above method not only provides a very convenient general method of estimating the platinum metals, but also throws interesting light on the formation of thiosalts and the precipitation of sulphides by their decomposition.