RESEARCH AND DEVELOPMENT CENTRE FOR STANDARD REFERENCE MATERIALS

SrCOa. The content of pure component in each of these substances was determined by classical chemical analysis. The temperatures and the heats of polymorphic transformations of these substances were measured with a Perkin-Elmer DSC-2 differential scanning calorimeter, and DTA studies were performed on a MOM 1500 D Q-derivatograph. The plot heat of transformation by DSC vs. DTA peak area is advanced as a calibration line for the approximate estimation of quantitative DTA effects. The substances studied will be certified as temperature standard reference materials for use in DTA and DSC. The thermal methods of analysis are today commonplace in studies of material properties, being applicable to virtually every substance, provided the apparatus used is of a suitable design and the conditions of the ex-periment are properly chosen. The great diversity of instrumentation a d ex-perimental procedures employed strongly affects the results, thereby creating the need for a common basis for relating independently obtained data and for comparing and calibrating all available instruments. A comprehensive effort relating to the standardization of the methods of thermal analysis has been launched by the International Confederation for Thermal Analysis (ICTA). Several ICTA-sponsored international research programs resulted in the certification of six sets of reference materials which are now available from the National Bureau of Standards (NBS). These were designed for calibration of the temperature axis in DTA, DSC and TG. The ICTA-NBS standards for temperature calibration in DTA and DSC encompass the range from-83 ~ to 925 ~ The reference materials at present recommended for calibrating the heat of transformation i DSC are two metals of high purity (tin and zinc) certified by the NBS and a set of six materials, comprising indium and five organic substances, upplie