COLLOIDS AN D LIFE 67 



plished either through the dispersion of non-dis- 

 persed or coarsely dispersed substances, or 

 through the condensation of molecularly dis- 

 persed systems. To these ends not only 

 chemical but mechanical, electrical and other 

 kinds of energy may be used."^ 

 Concerning the difference between colloids and crys- 

 talloidal solutions, Zsigmondy writes: "According 

 to Bredig solutions of crystalloids and colloids may 

 be distinguished by means of: 

 (a) diffusibility; 



(6) the work necessary to remove the solvent; 

 (c) electrical migration; 

 {d) coagulation; 

 (e) absorption; 



(/) irreversible changes of constitution and hys- 

 teresis ; 



{g) impermeability to other colloids; 

 {h) optical inhomogeneity; 

 (t) electrical formation of sols. 



*'It is evident from this brief r^sum4 that 

 there are many ways of distinguishing colloids 

 from crystalloids. Notwithstanding this, no 

 sharp line of demarcation can be established, for 

 there are numerous intermediaries between both 

 kinds of solutions. "^° 



» Theoretical and Applied Colloid Chemistry, 34, 35. 

 ^^ Colloids and the UUramicroscope, 11. 



