Temperature Calibration of DTA and DSC

Thermal analysis techniques are a class of analytical methods whereby where the nature of a sample is investigated in response to a 

Material Observed temperature C Corrected temperature C Lit. temperature c Deviation from lit. value/ C 

To establish a common basis for thermal analysis experiments, a series of ICTA (International Confederation for Thermal Analysis)-NBS (National Bureau of Standards) Standard Reference Materials were proposed via common experiments. These Standard Reference Materials have now been re-named ICTA Certified Reference Materials (CRM) and catalogued by the NBS (now NIST) as GM-758, GM-759 and GM-760 (see Table 1.4). The temperature standards of CRM are not the true transition temperatures of these materials, e.g. the difference between the extrapolated onset of a CRM and the equilibrium transition temperature is usually 3 C. 

These sets of materials have been adopted by a number of national and international organizations, among them the International Standards Organization (ISO), the International Union for Pure and Applied Chemistry (lUPAC) and the American Society for Testing and Materials (ASTM). 

The choice of material was restricted to those having first-order solid-state phase changes in the appropriate temperature ranges. Melting points were excluded because several types of specimen holders in common use could not retain liquids. A number of recognized melting point Standards (e.g. Pb, Zn) may contaminate thermocouples and sample holders through alloy formation, and decomposition processes were considered to be unsuitable because the atmosphere could not be controlled in many types of apparatus. 

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