18 CONDITION OF THE MIXTURE, 



name given when the volume increases exosmose, 

 when it diminishes. Very generally, however, we 

 attach to these terms the idea of the unknown 

 cause or group of causes which, in the given case, 

 produce the change of volume ; in the same sense 

 as that in which the term capillary action includes 

 the causes which determine the ascent of liquids in 

 narrow tubes. 



In all cases the increase in volume of the one 

 liquid is exactly equal to the decrease in volume of 

 the other, after making allowance for the contrac- 

 tion which the liquids undergo by simple mixture 

 (as in the case of alcohol and water, oil of vitriol 

 and water, &c.), as well as by evaporation. The 

 unequal concentration, or the unequal density of 

 the two liquids, has a decided influence on the 

 rapidity with which the change of volume takes 

 place ; but this cannot be viewed as the cause of 

 that phenomenon. In most cases the denser liquid 

 increases in volume, in others the reverse occurs. 

 The change When, for example, the tube contains brine, and 



of volume 



does not the outer vessel pure water, the brine, that is, the 



depend 



alone on denser liquid, increases in volume ; but when the 

 density of tube contains water, and the outer vessel alcohol, 

 the water, that is, the denser liquid, diminishes in 

 volume. 



With regard to the mixture of the liquids, the 

 bladder takes a distinct share in the process, inas- 

 much as it has pores, through which the two liquids 

 are brought in contact. 



