122 



improbalde if not iinposüihle j^reat dislaiice, vvliicli the centres of the 

 atoms slioiild have thou (see table I). 



The distance of the interfering particles calcnlated with (1) however 

 agrees with the distance of I lie centres of neighboni-ing molecides, 

 when we think ns these arranged as the centi-es of s[)heres packed 

 possibly close together. This distance is fonnd in the last column 

 of tabel I (i)/= molecniar weight, r/= density). Small deviations, 

 as far as they do not fall within the limits of experimental accniacy, 

 might be ascribed to deviations tVoni the spherical foim or to the 

 circumstance that will be discnssed in § (5. 



From this we think it justified to draw the conclusion, that the 

 intense diffraction ring found above is caused by the interference of 

 Röntgen light dilfracted by iieigbouring molecules ') '). 



For benzene too the above mentioned agreement between a and 

 the distance of neighbouring molecules arranged in closest packing 

 has been stated. From this we think it evident that the above con- 

 siderations also hold for this substance in contradiction with the 

 opinion of Dkbije and Scherrkr (I.e.) that this diffraction ring should 

 be due to the atoms in the molecule. 



^ 5. When ou>- view that the observed diffraction ring is due to the 

 interference of Röntgen light diffracted by neighbouring molecules 

 is right, the dimensions of these diffiacting particles may no longer 

 be neglected compai-ed with their mutual distaiice and we tnay ask : 



1) This does not involve that we have to do with the cooperation of only two 

 molecules at a time On the contrary, as far as it is not due to the particular 

 form of the relation betv^'een the quantity of Röntgen light and the blackening of 

 the film caused by it, the relative sharpness of the diffraction ring might point 

 at a cooperation of more molecules at a time. 



These molecules might then be arranged in the liquid in groups more or less 

 regularly under the influence of the forces wliich below the melting point condition 

 the regular structure in the crystalline state. 



In this way f.i. both rings of argon might he explained by assmning that in 

 tlie liquid a great number of groups is present in which the atoms are arranged 

 in a centered cubical lattice. The mentioned rings correspond then to the planes 



o 



(110) and (211), the edge of the lattice would be 4,65 A. For the distance of. 



o 



two neighbouring atom centres follows then again 4,0 A as in table 1. 



Because of the perfect analogy in the behaviour of oxygen and argon we should 

 have to replace for oxygen these atom centres by molecule centres. [Later 'experi- 

 ments have shown that the ratio of the values of sin V2 ^ for the two rings does 

 not quite agree with the ratio 1 : 1^3, as should be the case if the supposition 

 made above were valid. Added in the translation]. 



2) The possibility of this has already been acknowledged by Debije and 



SCHEEEER (I.e.). 



