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Chemistry. — ^'The metastahi/iti/ of the metak in consequence of 

 allotropy and its significance for Chemisfri/, Phrsics, and 

 Technics". II. By Pi'of. Ernst Cohen. 



The specific heat of the metals 1. 



1. In my first paper ^) on this subject I called attention to the 

 fact that the physical constants of the metals hitherto known, are 

 to be considered as entirely fortuitous values which depend on the 

 previous thermal history of the material used. 



In that paper I wrote with regard to the specific heat of the 

 metals: Considering, for instance, the important part which the 

 specific heats of the metals have played in chemistry and physics 

 during the last few years, it is evident that a revision of these 

 constants is wanted. 



2. Reviewing the earlier literature dealing with this constant, I 

 found that it contains already a number of data which prove unequi- 

 vocally that the specific heat of the metals does indeed depend on 

 their previous thermal history. 



Le Vrrrier published in the year 1892 a paper ^) "^sur la 

 chaleur spécifique des métaux", in which he desci'ibes his measure- 

 ments with copper, zinc, lead, aluminium, and silver. The calorimetric 

 deterniinations were carried out between 0° and 1000° by the method 

 of mixtures. The tem|iernlure of the metal at the moment at which 

 it was brought into the calorimeter was determined by means of 

 a Le Chateijer pyrometer. 



3. Le Verrier stated that the mean specific heat remains as a 

 rule constant till 200—300°, after which it changes abruptly, as 

 PiONGHON ') also found in the case of iron, nickel and cobalt. 



The variation of the total heat (i. e. the quantity of heat required 

 to raise the temperature of 1 gr. of the substance from 0° to t° C.) 

 with the temperature is consequently to be represented by a curve 

 with breaks and not by a continuous one. 



In the neighbourhood of these breaks the condition of the metals 

 is not only a function of the temperature, but also of their previous 

 thermal history. 



1) These Proc. 16, 632 (1913). 



2) a. R. 114, 907 (1892). 



3) G. R. 102, 675, 1454 (188Ü); 103, 1122 (1886;. in full: Ann. de Ghim. 

 et de Pliys. (6) 11, 33 (1887). 



