EXAMPLES OF CHANGE OF VOLUME IN LIQUIDS. 29 



of the same dissolved matters (unequal concentration,) acts in many cases, just as 

 if the liquids contained dissimilar substances. 



Although the experiments hitherto instituted, and the results obtained by FISCHER 

 (who first observed these phenomena,) MANGUS, DUTROCHET, and others, admit of 

 no comparison, since the apparatus used by them showed only relative change of 

 volume, yet a knowledge of some of these results is, nevertheless, of importance. 



When the two liquids are, diluted sulphuric acid (of sp. g. 1-093) and water, the 

 acid, at 50 F., increases in volume ; but if the acid have the specific gravity 1-054, 

 the volume of the water increases,* 



Diluted tartaric acid (11 parts of the crystalized acid and 89 of water) and water 

 mix through a bladder without change of volume ; with more than -11 per cent, of 

 acid, the volume of the acid increases ; with less that of the water. 



Solutions of animal gelatine, gum, sugar, and albumen increase in volume when 

 separated by a bladder from water ; and the increase of volume in these different 

 solutions, although of the same specific gravity, is very different indeed. When 

 the specific gravity ia 1-07, the increase in volume of the solution of gelatine 

 amounts to 3, that of solution of gum to 5, of sugar 11, of albumen 12. When a 

 solution of sugar (1 part of sugar to 16 of water) is separated by a bladder from 

 water, it increases in volume ; but if we add 1 part of oxalic acid to the sugar, the 

 water, on the contrary, increases in volume. If the amount of sugar in the solution 

 be doubled, the liquids mix without change of volume. A solution of sugar, separa- 

 ted by bladder from one of oxalic acid, rises, in the same time, 3 times higher than 

 when separated from water. (DUTROCHET.) 



From these experiments we obtain, as a universal result (which, however, requires 

 confirmation,) that an animal membrane possesses a less power of absorption for 

 solution of albumen than for all other organic substances :t and that a small amount 

 of mineral or organic acids increases the power transudation of water as well as of 

 the solutions of many organic substances.^ 1 ) 



The rapidity of mixture of two liquids, separated by a membane, depends on 

 the thicknes of the membrane, and stands in direct proportion to the velocity with 

 which the mixture formed in the pores and on both surfaces of the bladder changes 

 its place, and the original difference in the quality of the two liquids is renewed. 



|| If we suppose a tube, formed of a membrane (an intestine, for example,) and 

 filled with water, and if we assume that a current of saline solution flows round 

 this tube, in consequence of a mechanical force, the increase of volume of the brine 

 (the passage into it of a certain amount of water) will be effected in a far shorter 

 time than if the brine were not in motion. 



The velocity of transference will diminish with the amount of difference in 

 properties between the two liquids (the different amount or per centage of salt ;)^[ 

 it will be greatest at first, and diminish as the dilution of the brine increases, in 

 proportion, that is to say, as water is transferred from the contents of the tube to 

 the liquid without. 



The greatest effect, therefore, must occur and be permanent, when the water 

 transferred to the brine is continually again removed from it, that is, when the con- 

 centration of the brine is kept uniform.** To this end, if we suppose the membrane 



( ! )In order not to be misled in such experiments, we must avoid the employment of all 

 those liquids which alter the membrane in its chemical properties. Such are, for exam- 

 ple, acids of a certain concentration, nitrate of silver, salts of lead, chloride of gold, chlo- 

 ride of tin, chromic acid, bichromate of potash, taunic acid, &c. Even in water, the 

 properties of membranes generally undergo a change after some days, they then propa- 

 gate a far weaker hydrostatic pressure through their pores, and are no longer fit for 

 such experiments. 



* Examples of change of volume ; in acids, and neutral organic substances, according to 

 DUTROCHET 



t Membranes have a feeble power of absorbing solution of albumen. 

 t Effect of adding acids. 



j Causes which influence rapidity of mixture. 

 f| Motion of one of the liquids. 

 fi Difference in properties of the two liquids. 

 ** Effect of the continual removal of the transferred liquid analagous to suction. 



