332 BURGESS AND CROWE: NOTE ON RANGES OF PURE IRON 



adjust for a practically constant rate of heating and cooling over 

 the whole temperature range, 500° to 1100°C. Measurements 

 were taken at rates ranging from three seconds per degree to 

 thirty-six seconds per degree with no considerable effect upon the 

 location or magnitude of the critical ranges. The heating of the 

 furnace was by alternating current from a motor generator run 

 from a storage battery. The results are shown in the accom- 

 panying table; the analyses were furnished by Prof. C. F. Burgess 

 and Dr. H. Goldschmidt. It will be noted that for the remelted 

 samples the maxima for Ac2 and Ar2 are identical in position. 

 The plotted curves show Ac2 as pronounced as Ar2 for all the 

 samples. A2 and A3 appear to be different in kind, but the 

 discussion of this subject we prefer to defer until more complete 

 data and check analyses are obtained. 



It should also be noted that in 1909, A. Miiller^ published a 

 careful study of the critical ranges of electrolytic iron finding 

 Ac2 = 770°, Ar2 = 763°, Ac3 = 917° and Ar3 = 894°. 



' A. Muller, tJber die Darstellung des Elektrolyteisens, dessen Zuzammenset- 

 zung und thermische Eizenschaften. Metallurgie 6: 145. 1909. 



