A STUDY OF THE EFFECT OF PURITY ON THE USE OF NICKEL AS A TEMPERATURESTANDARD FOR THERMOMAGNETOMETRY

Samples of nickel, varying by four orders of magnitude in their purity , were studied by thermomagnetometry (TM), to determine if the extrapo lated end point (T(C)) changes. T(C) is virtually identical for the 99 .99 and 99.999% samples. Samples of less purity did show changes. Simu ltaneous DTA/TM can accurately define T(C) by comparing with the melti ng points of pure metals determined simultaneously. The melting points of lead and zinc bracket the T(C) for nickel. They were added to the sample pan prior to TM of nickel. Experiments were performed at heatin g rates in the range from 1 to 20 deg.min-1. It serves as a pilot stud y for the ICTAC Committee for Standardization to more accurately defin e the recommended values of T(C).