CHEMISTRY. 279 



the water in which the salt was dissolved. While the research is not 

 yet completed, the results so far obtained vary very little from an 

 average of 207. 16 (Ag = 107.88) for the atomic weight of lead. This 

 value is somewhat higher than that previously found by Dr. Wilson 

 in a similar way by analysis of lead chloride 207.10 (see Year Book 

 No. 6). Both investigations, however, agree in yielding results over 

 two-tenths of a unit higher than Stas's earlier one. 



In order to supplement the work concerning the atomic weight of 

 neodymium (see Year Books Nos. 8, 9, and 11), very pure praseo- 

 dymium chloride has been prepared and analyzed. Crude double 

 nitrate of praseodymium and ammonium, kindly loaned by the Wels- 

 bach Light Company, has been purified by fractional crystallization 

 through the efforts of Messrs. Whitcomb, Grimes, Wallace, and 

 Stewart. Nearly 4,000 crystallizations have been made in series of 

 about 25 fractions, the extreme fractions being occasionally rejected. 

 In this way neodymium was completely eliminated from certain 

 fractions so far as spectroscopic examination could determine. Mr. 

 O. J. Stewart has already converted to anhydrous chloride and 

 analyzed the purest fractions. As in the case of neodymium chloride, 

 praseodymium chloride seems to be converted into an insoluble modi- 

 fication by prolonged heating above the fusing-point. The fractions 

 examined up to the present time agree in yielding, as the atomic 

 weight of praseodymium, a value not far from 140.92. This value 

 is three-tenths of a unit higher than the one adopted by the Inter- 

 national Committee on Atomic Weights. 



Nearly 4 kilograms of caesium nitrate extracted last year from 

 Maine pollucite has been subjected to prolonged fractional crystal- 

 lization in a search for a strange element of the alkali family. As 

 might be expected from previous investigations this search was un- 

 successful. The extreme fractions when examined spectroscopically 

 showed no new lines and were not sensibly radioactive. 



Work has also been continued on the atomic weights of arsenic and 

 neodymium and on the change in volume which takes place during 

 the solution in water of certain salts. 



Jones, Harry C, Johns Hopkins University, Baltimore, Maryland. Grant 

 No. 847, allotted December 13, 1912. Continuation of investigaiions 

 on the absorption spectra of solutions and on the conductivity and dissoci- 

 ation of electrolytes in water and in nonaqueous solvents at different tem- 

 peratures. (For previous reports see Year Books Nos. 2-11). $2,200 

 The work on the absorption spectra of solutions, using the radio- 

 micrometer, has been carried out during the year by J. S. Guy 

 and H. C. Jones, with th'^ assistance of E. J. Shaeffer. The work 

 during the first half of the year had to do with the relative absorption 

 of light by pure water, and by an equal amount of water in the 

 presence of a dissolved substance. In a word, does the dissolved 

 substance have any effect on the power of the solvent to absorb light? 



