Attempt to Separate the Isotopes of Chlorine. 435 



Determination of the Equivalent of the Chlorine. 



The hydrogen chloride was converted into sodium chloride 

 by neutralization with sodium carbonate, and the equivalent 

 or.' the chlorine was determined by converting it to silver 

 chloride and determining the end-point of the reaction by 

 the nephelometer. The first experiments indicated that a 

 partial separation had taken place; but as the amount of 

 sodium chloride was insufficient to admit of recrystallization, 

 and the presence of any impurities would have given too 

 high a value for the equivalent of chlorine, the value was 

 very kindly redetermined by Mrs. D. L. Chapman in a 

 specimen of silver chloride which was thought to contain 

 an excess of the higher isotope, by reducing a known weight 

 in a current of hydrogen and weighing the silver produced, 

 thus eliminating - the effect of any impurities originally 

 present in the sodium chloride. The first determination 

 gave the value 35*458, and the hydrogen chloride obtained 

 in the reduction after reconversion to silver chloride gave 

 the value 35 '461 in a second determination. These figures 

 agree so closely with the standard value for the equivalent 

 of chlorine (35*46) that it is clear that no separation had 

 taken place within the limits of experimental error. This 

 was confirmed by preparing some hydrogen chloride in the 

 same apparatus with mi filtered light, and determining the 

 equivalent of the chlorine by the nephelometric method. A 

 value 35*59 was found, agreeing almost exactly with two 

 values found for hydrogen chloride prepared with filtered 

 light (35*59 and 35*58), thus showing that, in spite of the 

 precautions, the sodium chloride contained about 0*1 per cent, 

 of impurity. 



It is impossible to say whether the failure to effect a 

 separation is due to the secondary reactions mentioned 

 above or to the difference in the absorption spectra of 

 the two isotopes being insufficient for the purpose ; and 

 it is hoped to investigate this further by applying the 

 method to the chlorination of substances similar to mono- 

 bromtrichlormethane, in which case Noddack has found 

 that the secondary reactions do not occur (Zeit. fur Elektro- 

 chemie, vol. xxvii. p. 359, 1921). 



Balliol College, Oxford. 

 University College, Oxford. 



2 F 2 



