114 Dr. L. Silberstein on M.olecnla 



Similarly I find, for the interatomic distance R 3 in C = C, 

 taking N"'=N' + |ee =4-836 + 2*398 = 7-234 (again for the 

 D-line), 



K 3 = 0-9519 B/ = 2-610 A.U., 



i. e. again somewhat greater than R 2 - Thus R 1 <R 2 < R s , 

 and the minute increase of distance by 



AR = 14-i? 2 = 0-022A.U. 



accounts for the considerable difference 



AiV = j= minus |= =0*665. 



The above values of R ly R 2 and R s have been calculated, 

 by means of the formula 



/N— AN \V3 



R/R ' = (fcS > ) •' R =( 2 « N ») I/3 > • ( 2y ) 



from the values of JS r and i\ r for the D-line. If our theory 

 of atomic interaction (and the provisional assumption that 

 iV 7 = iVdiamond) is correct, then the values of i\ r and JY corre- 

 sponding to other wave-lengths should lead to the same 

 values of R^ R 2 , R%, or nearly so. Now, taking N 

 (i.e. N\ N", W") for the lines H a , H?, H y from Land.- 

 Born/s table, and iV from observations on diamond*, I 

 find, by means of (29), the results which, together with those 

 obtained a moment ago for the D-line, are collected in the 

 following table. All figures are in A.U. 



Calc. from i? 1 (c-c). i?.,(c=c). i? 3 (c=c). 



Hi 2-48 2'5S 5 2-60 6 



D 2-48 x 2-58 8 261 



H^ 2-48, 2-59, 261 8 



Ky 2-49 G 2-60 3 2-61 7 



This seems, in view of the roughness of the chemico- 

 optical data, quite satisfactory. There is but a very slight 

 systematic increase of the H lt R 2 > R 3 values from the red to 

 the violet line. The result contained in the above table 



* I. e. ju=2-4100, 2-4354, 2-4511 for H a , Up, H v respectively, whence 

 the corresponding values of iV : 2-105, 2126, 2-138. 



