MERCUROUS CHLORIDE BY HAROLD S. KING 123 



formula CI — Hg — Hg — CI for mercurous chloride were the 

 true one, then on dissociation one of the mercury atoms would 

 drop out of the molecule, presumably by thermal agitation, 

 carrying the electron pair with it. On the assumption that 

 the two mercury atoms differed in mass, one having the mass 

 number 197 and the other 204, to take an extreme instance, a 

 separation of isotopes would be accomplished, if there were any 

 selective action. It was thought that by gravitational attrac- 

 tion the electron pair between the two mercury atoms would be 

 somewhat more firmly held by the heavier mercury atom. In 

 this case it would necessarily be the heavier mercury that 

 formed the metal found as a product of the reaction. The 

 effect of mass on the position or orbit of an outer electron has 

 been proved by L. Aronberg, T. R. Merton and others'^ in 

 the case of lead. Though it is very small, it is conceivable 

 that it might exert a deciding factor in the dissociation, pro- 

 vided all other effects were equally balanced. 



However we have arrived at the conclusion that mercurous 

 chloride is not symmetrical in structure. If mercurous chloride 

 is formed when chlorine acts on an excess of mercury to give as 

 the primary product mercuric chloride which then adds an 

 atom .^f mercury to form the compound Hg = HgCl2, there 

 seems to be no possibility of separating isotopes by this method. 

 Such a separation would imply that the mercury had been added 

 selectively, which is inconceivable. Moreover there is very 

 little possibility of separating isotopes by this reaction even 

 if the old form of structure for calomel be true. G. Hevesy 

 and L. Zechmeister'^ have proved that in the case of lead 

 there is a dynamic equilibrium existing between ions and elec- 

 trons when the acetates of divalent and tetravalent lead are 

 mixed. They dissolved the tetraacetate of radioactive lead in a 

 solution of the diacetate of ordinary lead. After separating 

 the two forms of lead, they found that the divalent had become 

 radioactive while the tetravalent form had lost an equivalent 

 part of its activity. In other words there must exist an 



