486 A. P. Mathews 



residual valence; it may also involve, of course, the amount 

 of dissociation of the aggregates formed by cohesion or residual 

 valence. It is probable, since the atomic unions are as a rule 

 far more stable than the cohesive, the chemical attraction 

 between the atoms being of an electro-static kind, that the 

 union between solvent and solute due to the residual valence 

 is of far more importance than that of a cohesional nature, 

 just as the cohesional attraction is of vastly greater importance 

 than the gravitational attraction; and there are not lacking 

 indications that residual valence plays a very important part 

 in solubility. I may mention in this connection the series 

 helium to xenon already discussed elsewhere; the great dis- 

 solving power of associated as contrasted with non- associated 

 liquids, shown by the solvent powers of water; the less asso- 

 ciation of associating substances when dissolved in associa- 

 ting solvents as compared with their state in non-associating 

 solvents; the greater solubility of such gases as hydrogen 

 sulphide, ammonia, sulphur dioxide which have greater 

 residual valence than nitrogen, hydrogen and oxygen, and 

 the fact that they are known to combine with water, and so on. 

 The residual valence is hardly ever found to be a whole 

 number. The probable explanation of this is that the number 

 found represents only the average amount of residual valence 

 possessed by the molecules. It is probable that the residual 

 valences open up in pairs, one positive and one negative, 

 but that at any instant of time only a few molecules have them 

 open, so that the average amount possessed by each mole- 

 cule may appear to be a fraction. 



Summary 



The amount of residual valence of a number of non- 

 associating liquids and gases has been computed by sub- 

 tracting from the total number of valences which the mole- 

 cule possesses, as shown by its cohesion, the number which 

 there is reason to believe extend between the atoms of the 

 molecule. The difference is considered to be the residual 

 valence. 



