68 WH AT IS LIFE 



Colloids do not constitute a peculiar kind of 

 matter — as Graham, the founder of modern colloid 

 chemistry perhaps thought in taking account of their 

 dynamic qualities — but only a 'peculiar condition^ or 

 state, of matter (a fact to the establishment of which 

 P. P. von Weimarn especially devoted much labor). 

 Colloids are a peculiar state, or condition, of matter 

 that can be assumed by any substance, even by 

 salts, and that is independent of chemical constitu- 

 tion. 



Colloids are systems that consist of the "dis- 

 persion medium" (which usually is a liquid, but 

 which may be a gas or a solid) and the "disperse 

 phase." Minute particles of solids, droplets of 

 liquids, bubbles of gases — all may be colloidally 

 dispersed. There are therefor innumerable different 

 kinds of colloids. The simplest systems, of course, 

 are those in which a single element, say silver or 

 gold, is in the colloid state. But colloidal systems 

 are found in most various degrees of complexity. 

 Generally, research on colloids, whether in the arts 

 or in nature has to do with a mixture of colloids; i.e.» 

 not a single kind of particle but two or more varieties 

 of particles are present in colloidal solution. 



The colloid state is determined by the state of 

 dispersion, the size of the particles, of the disperse 

 phase. This size ranges from 1 to 100 millimicrons. 



