By comparison the Donaldson Iron is 2.80% C, 0.10% Mn, 0.061% P, 0.093% S and 0.39% Si. It has 0.76% graphitic carbon and 2.04% combined carbon and the thermal conductivity measurements come with a 2% error estimate. Tadokoro, Y., J., Iron Steel Inst. (Japan), 22, 399 — 424, 1936 and Donaldson, J.W., J. Iron Steel Inst. (London), 128, p. 255-76, 1933.