2921.     RUER, R, AND BODE, K.  [Magnetic Transformations of Ferromagnetic Metals.]  Stahl u. Eisen, vol. 45, 1925, pp. 1184-1189; Chem. Abs., vol. 20, 1926, p. 3426.

        Experiments were made with a view to find a fixed point at 700-800 for the purpose of calibrating thermocouples.  3 cooling curves and 1 heating curve for electrolytic Fe are given, that show an arrest point at 769.  Electrolytic Fe from the Langbein-Pfanhauser works showed the point at the same temperature.  Kahlbaum Fe in rods gave the point on heating but not on cooling and gave results midway between those for electrolytic Fe and mild steel.  The arrest is suppressed by impurities, but the impurity that is effective has not been identified.  The heat set free at the β-a change is 1/6 that at the γ-β change, or about 1 cal. per gm.  The change, which must be truly polymorphic, also occurs in Ni and Co.  As a- and β-Fe have the same space lattice, a polymorphic change does not necessarily involve a change in the space lattice, and the inverse must also be true.