658 



BURGESS AND KELLBERG : ALLOTROPY OF COPPER 



num is no more constant in its behavior than the copper, and 

 constancy is attained for both metals after a few heatings to 

 100°C. If they were now heated to a temperature higher than 

 100°C., their zeros would again change, and so on. 



TABLE I 

 Constancy of Zero Resistance of Platinum and Copper 



Professor Cohen also considers the specific heat experiments 

 of Le Verrier^ — who found discontinuities at about 360°, 575° 

 and 775°C. from a very limited number of as yet unconfirmed 

 observations — to strengthen his conclusions as to two modifica- 

 tions of copper. 



In 1907, Professor Benedicks'* showed that a supposed allo- 

 tropic form of copper discovered by Schlitzenberger'^ was not 

 copper. 



In view of the manifest importance of an allotropic phenome- 

 non in copper below 100°, if it really exists, we have executed a 

 series of experiments by an electric resistance method, in the 

 range to 100°C., similar to that described by us for iron,^ 

 substituting a calorimeter for the furnace. 



'Cohen, Trans. Faraday See, May 1915; Le Verrier, Comptes Rendus 114: 

 907. 1892. 



^ Carl Benedicks, Metallurgie 4: 5, 33. 1907. 



^ Schiitzenberger, Comptes Rendus 86 : 1265. 1878. 



* Burgess and Kellberg, The Electrical Resistance and Critical Ranges of 

 Pure Iron, Scientific Paper No. 230, Bureau of Standards, and Journ. Wash. 

 Acad. Sci. 4:436. 1914. 



