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CHEMISTRY OF PLANT LIFE 



Although the same general principles of physical chemistry 

 apply to all two-phase systems, the term " colloidal condition " is 

 commonly used only in connection with a particular type of dis- 

 persions, in which the dispersion medium is a liquid and the dis- 

 persed material is either a solid or a liquid. 



Thorough and careful studies have shown that when a solid or a 

 liquid is introduced into another liquid, and becomes dispersed or 

 distributed through it, the mixture may be either a true solution, a 

 colloidal solution, or a mechanical suspension. The characteristic 

 differences between these three conditions may be tabulated as 

 follows : although the significance of some of the phrases used will 

 not be apparent until the phenomena in question have been con- 

 sidered in some detail. 



1 1/x is one-thousandth of a millimeter; 1/yt is one-thousandth of a p, or 

 one millionth of a millimeter. 



It is recognized by all students of these matters that it is not 

 possible to draw a sharp dividing line between these three types of 

 conditions, and that they shade into each other, in many cases; 

 but in general it may be said that a colloidal solution is one in 

 which the dispersed particles are usually between 5juju and 200ju/i in 

 diameter, are difficultly or not at all diffusible through the mem- 



