On the Molecular Theory of Solution. 697 



surface tension of a solvent, so much the smaller, or the 

 greater, is the force with which it is attracted by the liquid. 

 Traube shows that when salts are arranged in order of their 

 cohesion pressures, as indicated by their effect on the surface 

 tension of water, practically the same order is retained in 

 the case of almost every property of solutions. 



I. Cohesion pressure. 



H < Cs <Rb < NH 4 < Li(hydrated) < K< Na < Li(dehydrated). 

 C10 4 <CNS<L 

 -C10,<N0 8 <C1. 

 Br < OH < F < SO, < C0 3 < Mo0 4 < W0 4 . 



II. Solubility. 

 N0 3 >C10 3 >I>Br>01>OH>S0 4 >C0 3 . 

 H > Cs > Rb > NH 4 > Li(hyd.) > K > Na. 



III. Capacity for hydration. 

 Cs < Rb < NH 4 < K < Na < Li. 



IV. Compressibility. 

 I>N0 3 >Br>Cl>OH>S0 4 >C0 3 . 

 H > NH 4 > Li (hyd.) > K > Na. 



V. Reduction of vapour-pressure, etc. 



N0 3 < CIO3 < CNS < Ci< Br < K S0 4 < OH < C0 3 < Mo0 4 

 Cs<Rb<K<Na<Li. [< W0 4 . 



VI. Depression of freezing-point. 

 N0 3 <CNS<CKBr, etc. 



Cs < Rb, etc. 



VII. Molecular volume. 



I > CIO3 > N0 3 > Br > 01 > OH > F, 

 etc. etc. 



In the case of organic liquids, Traube showed that their 

 solubility follows the order of (heir cohesion pressures 

 without exception. It will be seen later that this is 

 because the molecular cohesion of organic liquids is smaller 

 than that of water. Unfortunately for Traube's theory, the 

 solubility of solid substances follows the reverse order of 

 their cohesion pressures. 



