318 



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carried out and differing values have been found for the critical 

 absorption wave-lengths of the K and L series for this element. 

 KurthV values are X42.6^ (Ace. Pot. = 283 volts) and X 375^1 (Ace. 

 Pot. = 32.9 volts) respectively. Richardson and Bazzoni's^ value 

 for the K series is X43.4^ (Ace. Pot. =286 volts) while Mohler and 

 Foote's^ results for the K series give X 45.4^ (Ace. Pot. =272 volts). 



Hughes' value for the critical absorption wave-length of the K 

 series of carbon, it will be seen, is considerably higher than any of 

 the vailles found by the other investigators. 



In an investigation recently carried out by the authors in which 

 the method followed was that adopted by Hughes, the critical absorp- 

 tion wave-lengths of the K and L series were determined for the 

 elements boron, beryllium, and lithium and the critical absorption 

 wave-length of the L series for carbon. The apparatus used was 

 made of pyrex glass and is shown in Fig. 1. 



TO CLCCrROMETCR 



EAfiTH 



COCUNG 

 WATCR 



Fis. I 



H. Results 



The critical potentials found in the investigation for the elements 

 lithium, beryllium, boron, and carbon are classified by the authors 

 either as high or low range critical voltages. 



iKurth, Phys. Rev., Dec, 1921, p. 461. 



^Richardson and Bazzoni, Phil. Mag., Dec, 1921, p. 1015. 



'Mohler and Foote, Scien. Papers, Bur. of Standards, No. 425, 1922. 



