Pbysics. — ''The cri/stal strticture of gerinaniuin" . By Dr. N. H. 

 KoLKMEi.iKK. ((Jommmiieation N". I I from tlie Laboratory of 

 Physics and Physical Chemistrj of the Veteiinarj College at 

 Utrecht). (Communicaled bj Prof. H. Kamerlingfi Onnks). 



(Communicated at the meeting of April 29, 1922). 



§ 1. intvoduction. From a medical-biological point of view too, 

 a possibly complete knowledge of the qnadi-uvalent elements as f.i. 

 C and Si will be of great importance. The only one among tlie 

 elements of the fonrth gronp of the periodic system the crystal 

 strnctnre of which has not yet been investigated is germaninm*). 



For this reason the anthor nndertook the investigation of this 

 strnctnre with the same apparatns that had already been used in 

 the investigation of tin') and in that of NaClOj and NaBrO, *), that 

 has been described in preceding papers. Only the diaphragm of lead 

 in the camera was replaced by one of tin ^) while before it a Ni- 

 filter of 0,01 mm. thickness was placed in order to weaken the 

 /? radiation from the Cn-anticathode. The germanium (from Dr. Th. 

 ScHÜCHARDT, Görlitz), in the form of a fine powder, was cemented 

 to a thin glass rod, with Canada-balsam. 



§ 2. The crystal structure. The observations weie in good agreement 

 with a structure like that of diamond. In the table this is evident 

 from the satisfactory agreement between the values oï shi* ^6^) 

 derived from the observations with the calculated ones. For the 



o 



latter we chose as value of the lattice parameter a = 5,61 A. From 

 the density at 20°,4 viz. 5,459"), the atomic weight 72,418 ^ and 



o 



the number of Avogadro 6,062 . 10" we deduce a = 5,594 A. 



1) As has been remarked by D. Gostee (These Proceedings 21, 1294, 1919) 

 the knowledge of this structure might also be of importance for the question of 

 the eventual existence of binding rings of circulating electrons. 



*) A. J. BiJL and N. H. Kolkmeijer. These Gomm. Nos. 1 and 2. These Pro- 

 ceedings 21, 405, 494, 1918. 



*) N. H. Kolkmeijer, J. M. Bijvoet and A. Karssen. These Comm. N*^. 5, 

 These Proceedings 23, 644, 1920. 



*) W. H. Keesom and J. De Smedt. These Comm. Nr. 10. These Proceedings 

 25, 118, 1922. By a sufficiently high tension the L-radiation of the Pb might 

 namely be excited by the heterogeneous radiation of the Cu, which would cause 

 a blackening of the film. For tin this is much less probable. 



6) d is the angle between the rays incident on the substance and those diffracted 

 by it. 



«) Cl. Winkler, Journ. f. prakt. Ghem. 34, 177, 1887. 



7) J. H Muller, Journ. Am. Ghem. Soc. 48, 1085, 1921. 



