Physics. — "Oti the dijfracüon of Rontgen-rays in liquids". II. 

 By Prof. W. H. Keksom and Prof. J. Dk Smedt. (Commii- 

 iiicatioii N°. 12 from the Laboratory of Pliysios and Pliysical 

 Clieniistry of tlie Veterinary College). (Coniniiinicaled by 

 Prof. H. Kamkrlingh Onnks). 



(Communicated at the meeting of January 27, 1923). ■ 



§ 1. /ntroduc/oii. Tlie experiments on I lie diffraction of Rontgen- 

 rays described in (Jomni. N°. 10 ') were nil made with K^-rays of 

 copper. No dilfraotion ring was observed caused iiy tlie interference 

 of rays scattered by the separate atoms in the molecules. F.i. in the 

 case of oxygen tins might be ascribed to the circumstance, that the 

 distance of the cenli-es of the systems of electrons grouped round 

 the atom nuclei is too small to give an interference ring with rays 



o o 



of that wave length (viz. smaller than 0.95 A for A ^ 1 .54 A). 

 Therefore it seemed desirable to repeat some of the experiments 

 with rays of a shorter wave length. 



We have now made several observations with K^-rays of molyb- 

 denum (^ = 0.71 A). 



^ 2. For method and apparatus see Comm. N°. 10. The rays 

 emitted by the molybdenum anticathode were tillered by 0.35 mm. 

 zirconium. 



^ 



^ 3. Results of the observations on the principal diffraction ring. 

 We now exposed liquid oxygen, argon and nitrogen, also water and 

 carbonic disulphide. 



For oxygen, argon, water and nitrogen (investigated for the first 

 time now) we found confirmed that the principal ring is due to 

 neighbouring molecules, which we may consider to be distributed 

 approximately as spheres packed together as closely as possible and 

 tilling up the space occupied by the liquid. 



This time we obtained a diffraction ring for carbonic disulphide 



>) These Proceedings 25, 1922, p. 118. 



