DEDUCTION FKOM THE GASEOCS THEORY OF SOLUTION.* 



BY PROF. ORME ^lASSON. 



Before passing on, let me briefly recnpitnlate the chief points in 

 Yau't Hoff's g'aseous theory of solution and the experimental laws on 

 T\liich it is based. 



(1) In every simple solution the dissolved substance amy be re- 

 garded as distributed thioughout the whole bulk of the solution. Its 

 total volume is therefore that of the solution, the solvent playing the 

 part of so much space; and its specitic volume is the volume of that 

 quantity of the solution whicli contains I gram of the substance. To 

 avoid confusion, it is best to s})eak ol" this as tiu' specific solution 

 volume {v) of tin' substance. It is obviously in inverse ratio to tiie 

 concentration. 



(2) In every simi»le solution the dissolved sul»stance exerts ;i (h'fiuife 

 osmotic pi'es.siirc {p). This is normally independent of the nature of 

 the solvent. It varies iuvorsely as the si)ecific solution volume (<u' di- 

 rectly as the concentration), and directly as the absolute t<'mt)erafur(^ 

 (T). We ma>' then write for solutions, as we do for gases, tliee(|uation 

 2),r=)\ 7', where /> and r hav<' their speciali/.ed meanings, and >• is a, 

 constant foi- each soluble substaiu-e, 



(."}) The molecular solution \'olunu' of all dissolved subsiaiu'cs is the 

 same if they are compared at the same t<'mperature and osmotic press- 

 ure, if in be the molecular weight, )» . r — Tis the molecular solution 

 volume; and we can now write, as we <lo for gases, /> ]\= /,'. '/', where 

 Ji is the same constant for all substances. 



(4) This constant /t has the same value when tin' toiinnla is applied 

 to the dissolved state as wlien it is applied to the gaseous slate itself. 



(5) The gaseous law^s, as I have stated them, are not absolutely true 

 for dissolved matter in all cinaimstances. J)issociation often occurs, 

 as it may occur in the process of vapcuization, thus causing a])i)arent 

 exceptions, but apart from this there are and must be variations from 



* Pii it of iiii address delivered t)y the President r)l' Section I? of the Ansiraliau 

 Asociation for tlie Advaneenient of Science, Jannary, 18!)1. (From Xaliirc, Fcl>. 12, 

 1«91; vol. XMii.,].]). 315-31!).) 



H. Mis. Ill IJ) 2«9 



