384 CARNEGIE INSTITUTION OF WASHINGTON. 



The arrangement of the atoms in crystals of potassium cyanide 

 (KCN) has been determined by Mr. Bozorth. It has led to the inter- 

 esting conclusion that the carbon and nitrogen atoms are located close 

 together, so as to form a group centered in a position corresponding to 

 that occupied by the chlorine atoms in potassium chloride. Whether 

 there is a measurable separation of the carbon and nitrogen atoms from 

 one another could not be fully determined. 



Progress is being made in improving the method of measuring the 

 intensities of X-ray reflections through the work of Mr. Badger, who 

 is studying how the intensity varies with the character of the crystal 

 surface, thus whether the surface is natural, results from cleavage, or is 

 produced by rough grinding or fine polishing. A photo-electric appa- 

 ratus to determine intensities by measuring blackness of photographic 

 spots or lines produced by reflected rays is being developed. 



Richards, Theodore W., Harvard University, Cambridge, Massachusetts. 

 Continuation of exact investigation of atomic weights and other physico- 

 chemical properties of elements and of simple compounds. (For previous 

 reports see Year Books, Nos. 2-19.) 



(1) The Separation of Lead Isotopes. 



Considerable progress was made in this investigation, with the help 

 of Mr. Harold S. King. The fractionation of lead by the Grignard 

 process has now progressed far enough to make it worth while to 

 determine the atomic weights of the several fractions of which consid- 

 erable amounts are at hand. This time-consuming process having 

 been completed, the determinations will be made in the autumn. 

 Another method also has been undertaken: fractionation by volatili- 

 zation at a comparatively low temperature in an X-ray vacuum. 

 Enough of this volatilized material is now at hand, likewise, to make a 

 determination of the atomic weight. Diffusion methods have also 

 been subjected to careful analysis and an apparatus, calculated to 

 give a maximum efficiency, has been devised. 



(2) The Atomic Weight of Rubidium. 



Miss Edith H. Lanman, a graduate student of Radcliffe College, 

 continued the study of the atomic weight of rubidium, preparing new 

 samples from other sources by fractional crystallization of the dichlor- 

 iodide. She continued further an elaborate investigation, guided by 

 careful spectroscopic analysis, with the aim of eliminating csesium — a 

 diflScult process because of the great similarity of the two metals. 

 The outcome seems to have been successful and the determination of 

 the atomic weight has already been begun. 



(3) The Atomic Weight of Gallium. 



Mr. W. M. Craig prepared a new series of fractions of gallium chlo- 

 ride, even more carefully than before, because of the experience gained 

 in the earlier purifications. He began the determination of the atomic 



