DTA and quenching methods in the system CaO-CO_2-H_2O

Abstract

Harker (1964) recently described a simple technique for differential thermal analysis in closed systems containing volatile components under pressure, which promises to be of great utility. He contrasted the reaction temperatures recorded in his preliminary studies with those reported in the same systems by quenching techniques, and he noted some rather large temperature discrepancies. This led him to conclude that the accuracy of the quenching technique in systems where the liquid phase cannot be quenched to a glass "is often somewhat low and sometimes quite misleading." However, if the melting temperature of portlandite recorded by Wyllie and Tuttle (1960) is corrected as shown by Gittins and Tuttle (1964), the results obtained by DTA and quenching techniques are almost identical, and Harker's concern for the validity of the quenching technique becomes unnecessary, in this system at any rate. This note contains revised values for melting reactions in the system CaO-CO_2H_2O measured by one of us (EJR) using the quench technique, and a discussion of this technique and DTA by the other (PJW).

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