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Saburo Umino

• The heat content of 19 kinds of iron-carbon alloys ranging from 0.07 to 5.07% carbon were measured at each of different high temperatures up to beyond the melting point by the method of mixture, and their mean and true specific heats were deduced therefrom. From the relation of the heat of peritectic reaction and carbon concentration, a value of 14.7 calories was given as the heat of reaction per gram of the specimen in 0.13% carbon, and the heat of solution of gamma-crystal below 0.13% carbon into delta-crystal decreases with the rise of temperature. The heat content and specific heat of cementite at high temperatures were found by extrapolation of the present results, and the heat of Ao transformation of cementite was estimated to be 9.35 calories. The heat of fusion of delta-crystal to melt into the liquid of the conesponding carbon concentration is 64.90 calories per gram of gamma-crystal in 0.07% carbon. and 65.31 calories for that in 0.03% carbon. The heat of fusion of gamma-crystal on the solidus to melt into the liquid of the corresponding carbon concentration is 57.80 calories per gram of gamma-crystal in 1.70% carbon, and 67.19 calories for that in 0.13% carbon. As the latent heat of fusion of eutectic alloy was found to be 60.91 calories per gram. The heat of transformation of alpha- into gamma-iron at the As transformation point was calculated to be 5.59 calories· per gram for pure iron and 16.60 calories at 7200 for eutectoid steel, respectively. The heat of solution of cementite into gamma-crystal of 0.90% carbon is 11.15 calories per gram at 720°, and decreases with the rise of temperature and carbon concentration of gamma-crystal. The latent heat of fusion was obtained as the limiting value of the heat of fusion, and the former is always somewhat less than the latter. The latent heat of fusion of cementite was found to be 65.0 calories per gram, the melting temperature being estimated to be 1600°. The heat of mixture of any two liquids or solids in the iron-carbon system is proportional to the product of their quantities a and b, and inversely proportional to the sum of these quantities, being always endothermic reaction. So the heat of mixture H1 in these cases will be given as follows H1 = K (ab/(a+b)) where K = f(t) [(C1-C2)exp2] The proportional constant K is a function of temperature and the square of the difference of carbon concentrations C1 and C2 of two liquids or solids.