505 



Chemistry. — '^'Tlie allotropy of zinc." I. By Prof. Ernst Cohen 

 and W. D. Helderman. 



As long as lialf a century ag'O xarions investigators tried to solve 

 the problem whether zinc might be capable of existing in different 

 allotropic modifications.^) As late as 1890 Le Chatelier^) proved 

 that this metal does really show a ti-ansitionpoint in the neigh- 

 bourhood of 350°. Mönkemeyer^) found this point at 321°, Benedicks") 

 at 330° (melting point of pure zinc 41 9°.4) whilst the measurements 

 of Max Werner ^) (who found 300°), published some weeks ago, 

 agree sufficiently with those of Le Chatelier. We shall discuss in 

 a subsequent paper the differences which exist amongst the results 

 of the investigators mentioned above. Whilst Benedicks mentions a 

 second transitionpoint (at 170°), Max Werner was unable to find 

 this point. The question whether it really exists or not may be left 

 open for the moment. 



As long ago as 1806 Charles Hobson and Charles Sylvester ^) 

 stated that the mechanical properties of zinc are very different in 

 different ranges of temperature. It may be pointed out here (as also 

 stated by ourselves) that zinc which is hard at ordinary tempera- 

 tures, becomes extremely brittle after having been melted and 

 chilled. 



Most of those who have studied this metal, point out that the 

 values which are given in the literature for its density differ amongst 

 themselves very considerably. 



This fact has formed the starting point for the researches of 

 Kahlbaum and his collaborators^) (following a way indicated by 

 Spring) on the influence of very high pressures on the density of 

 metals in general. We shall discuss this question in a special paper; 

 here it may be pointed out that ^■ears ago Bolley ^) as well as 

 Rammelsberg '') carried out some experiments in order to find out 



1) The earlier literature on this subject will be given in our paper in the 

 Zeitschrift fur physik. Chemie. 



2) C. R. Ill, 414,454(1890). Contribution a l'étude des alliages, Paris 1901, p. 416. 



3) Zeitschr. f. anorg. Chemie, 43, 185? (1905). 



■^) Arkiv for Matematik, Astronomi och Fysik, 6 (1910), quotation from a separate 

 copy Metallurgie, 7, 531 (1910). 



5j Zeitschr. f. anorg. Chem. 83, 275 (1913). 



6) Nicholson's Journal of Natural Philosophy, 11,304 (1806). Translation in 

 Gehlen's Neues allgemeines Journal der Chem.ie, 6, 728 (1806). 



7) Zeitschr. f. anorg. Chemie 29, 177 (1902). 



8) Liebig's Annalen, 95, 294 (1885). 



9) Monatsberichte der königl. preussischen Akad. der Wiss. zu Berlin, 1880, 

 pag. 225. 



