Mi:. CLIVE CUTHBKRTSON AND MAUDE CUTHBERTSON ON THE 



Tli-- average temperature of our experiments was 19'4 C. and at that temperature 

 the molecular volume of chlorine would be 22038'9 c.c. That of hydrogen is 

 _'L' 1^8'8 c.c. Hence the refractivity observed must be multiplied by the ratio of these 

 immlwrs. We thus arrive at the number '00078412; and since the accuracy of the 

 i-\|M-rinu*ut8 is not greater than 1 part in 1000 we may accept '000784 as the 

 n-t'ractivity of chlorine for the green mercury line. 



Dispersion. Assuming this value, the dispersion was measured at seven other 

 points of the visible spectrum by the method described in previous papers.* 



The following table shows the results : 



TABLE I. Dispersion of Chlorine. 



The numbers shown in the column headed "calculated" are derived from the 

 formula 



( M _l) D 7-3131x10* 



Kw) 9629 '4 xlO-' 



i 8 the frequency of the light, i.e., = X - _j xl lu 



XX (in cm.) 



M^mW ,o -W^W-The absorption spectrum of chlorine has 

 -nveafgated by Ifa. LA.RD.t She describes the spectm m aa con 8 isting of 

 of general abeorpt.on which extends, in a column of ga s 60 cm long 

 .50 to A 2599, and lengthens in hoth directions with increasing preZa but 



* .L7 L 8 , ^ rangibk 6 " d ' reaChi " X 4 " "' ^ 25Z?2 

 .pectrum ly.ng between A 4799 and X 5350 which consists of * of da, 



* fce Roy. Soc. Proe.,' vol. 83, p. 152, 1909. 

 'Aatrophyi,. Journal,' 14, p. 85, 1901. 



