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G. J. BORROWS. 



altered, and a further volume change result. This second 

 change may be in the same direction as the first or it may 

 be in the opposite direction, depending on the relative 

 magnitudes of the specific contraction accompanying the 

 formation of solvate in each case. 



In order to explain the results obtained in this work we 

 would therefore have to consider that the formation of 

 solvates is characteristic of all the substances that have 

 been used as solutes. It is considered that the results 

 obtained in this research can be explained by assuming 

 that the observed volume changes result from a rearrange- 

 ment of the molecules in the system. 



From a consideration of the specific solution volumes of 

 organic solutes in organic solvents Tyrer (loc. cit.) con- 

 cluded " that a connection exists between the compres- 

 sibility of a solvent, and the volume which a solute, when 

 dissolved in it, takes up." In the case of solutions in 

 water alcoholmixtures there isundoubtedlysome connection 

 between the specific contraction that has already taken 

 place in the preparation of the mixture and the specific 

 volume of a solute in this mixture. 



The contraction which results from the mixing of water 

 and alcohol is due to a condensation in the volume of the 

 system resulting from a rearrangement of the molecules 

 in such a way as to permit of closer packing. For any two 

 liquids (e.g., alcohol and water) this condensation will tend 

 towards a maximum corresponding to a certain mixture at 

 any particular temperature. The effect of dissolving a 

 solute in such a mixture will depend on the relative size 

 of the molecule of solute, and the amount of condensation 

 that has already taken place in the preparation of the 

 solvent. In the case of the pure solvents (water or alcohol) 

 the addition of solute will cause a rearrangement of mole- 

 cules in the system resulting in a relatively large decrease 



