CHEMISTRY. 249 



the intensities of the various parts of a band within the wave-lengths that 

 could be photographed, but could extend the work far down into the infra- 

 red. The most sensitive photographic plate is limited by the wave-lengths 

 A 2000 to A 8000. By means of the radiomicrometer we could easily work 

 as far down as A 20,000 and have planned for extending the measurements 

 to much greater wave-lengths. We have already detected and measured the 

 intensities of a number of new bands in the region of greater wave-lengths, 

 and our work in this field is, comparatively speaking, only begun. 



By means of the radiomicrometer we can work quantitatively in the field 

 of absorption spectra, and have extended the range of such work about 2^2 

 times. We have studied a number of salts of neodymium and praseodym- 

 ium. The following interesting and important relation has been found : For 

 the more dilute solutions the center of the absorption bands moves towards 

 the longer wave-lengths, and the intensity of the bands becomes greater. A 

 suggestion to account for these facts appeared in a paper recently published. 



The work next year with the radiomicrometer will deal with a much 

 larger number of aqueous solutions of inorganic and organic compounds ; 

 with a large number of substances inorganic and organic in non-aqueous 

 solvents; with the effect on the intensities of the bands, of temperature, 

 dehydrating agents, etc. 



The study of the conductivity and dissociation of electrolytes at different 

 temperatures has made good progress during the past year in the hands of 

 Dr. Wightman, Dr. Kreider, Dr. Howard, Dr. Springer, Mr. Smith, and 

 Mr. Shaeffer. The results of this work, which has been in progress in this 

 laboratory for about a dozen years, has been published as monograph No. 

 170 of the Carnegie Institution of Washington. 



During the past year the work on the organic acids has extended over the 

 whole range of temperature from o° to 65 °, but most of the work has been 

 done between 35 ° and 65 °. Many of the more common organic acids have 

 been studied with respect to their electrical conductivity, over the tempera- 

 ture range above indicated, and over a range in dilution from the most con- 

 centrated solution that could be prepared up to from y^ 1 ^ to ^^^ normal. 

 The dissociations have been calculated whenever possible, and the constant 

 for the acid worked out wherever it existed. 



The temperature coefficients of conductivity were calculated both in con- 

 ductivity units and in per cent. Knowing the constants of these substances 

 we know exactly what they will do as acids, under all conditions, and this is 

 the most important reason for carrying out this investigation, especially as 

 it is the first systematic investigation in this field over any considerable 

 range in temperature. 



The work with the salts has this year been practically limited to those 

 cases which are more or less exceptional and which have given more or less 

 trouble in the earlier work. These include those salts which are decomposed 

 at more elevated temperatures, especially those hydrolyzed by water. 



