Physics. — "Investigation hij means of X-ra.>js of the cnjstal- 

 stnictare of lahite and grey tin. 1". Commmiication N". J from 

 the Laboratoi-y of Physics and Physieal Chemistry of 

 the Veterinary College at Utrecht. By A. J. Bij], and 

 N. H. KoLKMEiJER. (Coniinunicaled .in behalf of Prof. 

 W. H. Keesom, Directoi- of the Laboratory, by Prof. 

 H. Kamerlingh Onnes). 



(Communicated in the meeting of June 29, 1918). 



Till now three methods of investigation by means of X-rays of 

 the inner sti'ncture of crystals have been nsed. That of Friedrich, 

 Knipping and L'aue ') and that of the Bragg's *) can only be used, 

 when rather large, well-formed crystals, of which the crystal-system 

 is known, can be procured. On the contraiy the use of Debije and 

 Scherrer's ^) method requires a great number of differently orientated 

 minute crystals"*). For that reason this method is the most adapted 

 for the investigation of the crystal-structure of those materials that 

 are not or only with difficulty obtainable in larger crystals, e.g. of 

 those metals — eventually of those modifications of those metals — 

 that are only liuown in a micro-crystalline state. Another example 

 of the probable applicability of the method of Debije and Scherrer 

 is found in the solidified gases, which till now are not to be 

 obtained in sufficiently large crystals of exactly defined orientation. 



The investigation of different modifications of the same material, 

 e.g. allotro[)ical states of an element, is specially interesting. This 

 investigation has already been initiated by Olie and Bul, who 

 published lately in these Proceedings their interference-photos of 

 gi-aphite and diamond. *) In the meantime Debije and Scherreir ^) 

 investigated the same materials and also so called amorplious carbon 



1) W. Friedrich, P. Knipping and M. Laue, Sitz.-Ber. d. K. Bayer. Akad. d. 

 Wiss. Math.-Phys. Kl. 1912, p. 303. 



2) W. H. and W. L. Brac4G, X-Rays and Crystal-Structure. London, 1916. 



3) P. Debije and P. Schereer, Nachr. d. K. Ges d. Wiss. zu Göttingen. Math, 

 Phys. Kl. 1916, p. 1. 



*) A. W Hull, Phys. Rev. (2) 10 (1917), p. 661, evidently arrived independently 

 of Debije and Scherrkr, at rather the same method. 



6) J. Olie and A. J. Bijl, Proceedings Roy. Ac Amst. XIX (1917),p. 920. 

 «) P. Debije and P. Scherrer, Physik. ZS. 18 (1917), p. 291. 



