LECTURES.. 215 



one liquid into another through the pores of the suhstance which 

 separates them. The effect is due to an elective ca])illary attraction 

 and a subsequent mixing of the liquids. A bladder can he soaked 

 with water, but is merely infilmed with alcohol — hence the more rapid 

 transmission of one of these liquids through this membrane than the 

 other. 



Same result produced with other liquids, provided they have 

 diiferent degrees of attraction for the membrane, and a strong ten- 

 dency to mix with each other. 



The endosmometer exhibited. 



(109.) The endosmose, (or flowing in) of the exterior liquid is 

 generally accompanied by the exosmose {e^co and coaixo:: or flowing 

 out) of the interior liquid, but to a much less extent, the difference 

 depending upon the greater or less attraction for the interposed sub- 

 stance. 



Modifications of this action perform an important part in many of 

 the operations of vegetable and animal life. 



Method of strengthening wine by a bladder over the mouth of the 

 bottle. 



Endosmose probably takes place to a slio;ht degree, between gases 

 in their transfusion through porous substances, although most of the 

 phenomena of this kind can be explained on the principle of a differ- 

 ence in weight, and Dalton's law of diffusion. It is, however, certain 

 that capillary attraction does take place in an eminent degree between 

 solids and gases. Newly burnt charcoal absorbs 90 times its bulk of 

 ammoniacal gas, 35 times of carbonic acid, and 9.2 times of oxygen. 

 The gas in some of these cases must be condensed by the attraction 

 into a liquid. 



(110.) Chemical Attraction, 



Or, as it is generally called, chemical affinity, is the highest degree 

 of heterogeneous attraction — it takes place between the component 

 molecules of different kinds of matter, and produces other matter of 

 entirely diiferent qualities. 



The peculiarities of this attraction are as follows : 1. It is elective; 

 the intensity of action is not the same between all bodies, so that one 

 substance may displace another in a compound by its superior attrac- 

 tion for the other ingredient. 2. It is definite ; the same quantity of 

 any substance has the same saturating power in reference to all matter 

 with which it combines. 3. It determines the pecidiar -projjerties of 

 the compound. In these peculiarities it differs materially from gravi- 

 tation, the intensity of which is the same for all matter, and does not 

 admit of saturation, the attraction of a for h does not interfere with 

 the attraction of a for c. 



The operation of this attraction is intimately connected with the 

 electricity, ajid will be referred to again under the head of galvanism. 

 It forms an essential part of chemistry, and its peculiarities are fully 

 described and illustrated in that branch of science. 



