CHEMISTRY. 247 



Fractions i + 2 -j- 3. the least soluble, contain a trace of samarium, which 

 is undoubtedly the cause of the slightly higher value obtained from this 

 material, while fractions 12 to 15, the most soluble, contain a trace of pra- 

 seodymium, which would lower the observed atomic weight of neodymium. 

 Until these impurities can be estimated, the above figures are subject to 

 slight uncertainty. At any rate, they agree very well with the final corrected 

 value previously obtained by Baxter and Chapin, 144.275. 



Pure praseodymium salt also has been prepared from about 20 kilograms 

 of crude praseodymium ammonium nitrate furnished by the Welsbach Light 

 Company through the kindness of Dr. Miner. This material has already 

 been subjected to 3,500 crystallizations and is almost ready for analysis. 



Mr. F. L. Grover has commenced further investigation of lead bromide 

 in the hope of obtaining the compound in a state sufficiently definite for 

 atomic-weight investigation. 



Mr. C. C. Wallace has investigated the change in volume which takes 

 place when the chlorides, bromides, and iodides of lithium, sodium, potas- 

 sium, rubidium, and caesium are dissolved in water at various concentrations 

 and various temperatures. The results indicate interesting relationships 

 with various physico-chemical properties of the elements and compounds 

 involved. Incidentally a considerable quantity of caesium salts has been 

 extracted from mineral sources and will be used for the redetermination of 

 the atomic weight of caesium as well as in the examination of the physico- 

 chemical properties of its salts. 



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

 No. 753, allotted December 15, 191 1. Investigation of the absorption 

 spectra of solutions, $1,200. Grant No. 718, allotted March 23, 1911. 

 Researches on the conductivity, dissociation, and the temperature coeffi- 

 cients of conductivity and dissociation of the more common electrolytes, 

 $1,000. (For previous reports see Year Books Nos. 2-10.) $2,200 



The work of the past year, with Dr. J. S. Guy, on the absorption spectra 



of solutions has had to do with the following problems : 



(i) The effect of high temperature on the absorption spectra of aqueous 



solutions. 



(2) The question as to whether ions and molecules in solution show the 

 same or different absorption spectra. 



(3) The measurement of the intensities of absorption lines and bands by 

 means of the radiomicrometer. 



The problem of the effect of high temperatures on the absorption spectra 

 of non-aqueous solutions was studied last year, in a steel tube closed at both 

 ends with glass or quartz windows. The steel apparatus was covered elec- 

 trolytically with gold. While this form of apparatus was very satisfactory 

 with non-aqueous solutions, it did not work satisfactorily with aqueous 

 solutions, since the water-vapor, under the high pressure, found its way 



