326 CARNEGIE INSTITUTION OF WASHINGTON. 



extra electroscope, further refinements of the apparatus have now been 

 worked out which have made possible more accurate measurements of 

 the intensities of the X-ray reflections. A method has also been devel- 

 oped for growing larger, more perfect crystals. A redetermination of 

 the relative intensities of the several orders of reflection has been made 

 for the simplest arrangement of atoms, and work is in progress on the 

 effect on the intensities of the variation of molecular weight in a series 

 of simple crystals (such as those of potassium chloride, bromide, and 

 iodide). 



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 2-17.) 



On account of the war, investigation in purely scientific matters was 

 almost at a standstill during the early part of the winter. The aca- 

 demic year opened with only one assistant at work in the laboratory 

 in addition to the army officers of the Sanitary Corps who were com- 

 pleting the investigations on the physico-chemical properties of the 

 constituents of cereals, mentioned in the last report. This investiga- 

 tion was completed in November. After the first of January several 

 former students returned from the army, and two new assistants were 

 secured, but so far there has not been sufficient time to permit much 

 finished work. The following investigations have been conducted: 



(1) The Atomic Weight of Radioactive Lead from Japan. 



Through the kindness of Professor Ikeda, a small specimen of a lead 

 incrustation from a radioactive spring at Hokuto, Japan, was obtained, 

 and Dr. J. Sameshima studied its atomic weight. The sample con- 

 tained numerous impurities, and the purification of the small amount 

 was difficult. The purest preparation yielded an atomic weight of 

 about 207.13 instead of 207.2, the atomic weight of ordinary lead, 

 showing that this radioactive spring in Japan contains only a small 

 proportion of the isotope of lead which now bears the name of Radium 

 G. The method was essentially the same as that used in previous 

 investigations. 



(2) The Purification of Gallium by Distillation as the Chloride. 



With the help of Mr. W. M. Craig, this method of purifying gaUium 

 salts was carried further, especial attention being given to the impur- 

 ities which may be present in the initial and final fractions. Further 

 description may well be postponed until the next report, when it is 

 hoped the details will have been more fully studied. Incidentally it 

 was found that one of the best methods of freeing gallium from zinc 

 is by heating the liquid metal in a quartz tube in a high vacuum to a 

 high temperature (over 1000°), when the zinc distils, carrying with it 

 only a very small amount of gallium. 



