LIQUIDS THROUGH A MEMBRANE. 23 



centrated, the other with a more diluted solution, 

 the change of volume in the two liquids continues. 



As appears from these experiments, the change 

 of volume depends on a difference in the cha- 

 racter of the two liquids which are connected 

 through the bladder; and the time during which 

 change of volume occurs is in direct proportion to 

 the time during which this difference in character 

 subsists. The greater the difference in character 

 and composition between the liquids, and the more 

 rapidly this difference is renewed by the exchange 

 between the strata in contact with the opposite sides 

 of the bladder, the more rapidly does the one liquid 

 increase, and the other diminish in volume. 



The following apparatus is very convenient for The change 

 measuring the change in volume, caused by the maybe 

 mixture of two liquids separated by a membrane. 



The tubes a and b (Fig. 5) are of 

 equal width, and are best taken from 

 the same tube ; a is closed with bladder, 

 and filled up to a certain point with the 

 liquid whose increase in volume is to be 

 determined. It is then fitted by means 

 of a good cork into the wider tube c, 

 which contains distilled water, care 

 being taken to exclude all air-bubbles. 

 At d lies a small lead drop, which acts 

 as a valve in shutting the opening of 

 the capillary tube connecting c with b. 

 Pure water is now poured into b, and 



