RI 2917 The Melting Point Of Potassium Chromate

The American Society for Testing Materials4 has recommended that the melting temperature of potassium chromate be used-for indicating the temperature to which a coal sample should be heated in the standard method of analysis to determine its volatile matter content. The specified temperature is 950± 20° C., the melting point of potassium chromate being noted as 940° C. Le Chatelier5 originally found the melting point to be 975°; later6 he found 9400. According to Shemtschushny7 the melting point is 984°; he also found a transition at 679°. Groschuff8 found the melting point to be 971° and the transition temperature 679°. Amadori9 reports a melting point of 9.78° and a transition point of 666°. The International Critical Tables10 take the melting point as 975°, which is estimated to be correct to two significant figures. In view of the apparent uncertainty existing, it has been though worthwhile to make a careful redetermination of this datum. It is of interest not only to determine the melting point of the pure salt, but also of the commercial product, in order to test its suitability for use as a temperature indicator. The work was suggested by A. C. Fieldner, chief engineer, experiment stations division, U. S. Bureau of Mines.