OSMOTIC PRESSURE OF COLLOIDS 43 



111 solutions ol" the third class, the O.P. and otlicr coUigativc 

 properties point to a reduction in the number ol" j)artieles in 

 solution. A clubbing ol" molecules has taken place. Because most 

 of the substances that compose this group have a somewhat gluey 

 consistency, Ciraham called them colloids (Gr. koXXi-j = glue). The 

 physics of colloidal complexes will be dealt with in a separate 

 chapter. Here we merely wish to draw attention to their low 

 osmotic pressure. Colloid substances may be converted into non- 

 colloid or crystalloid derivatives, and so liberate energy, e.g. 

 starch, a colloid having a very low osmotic pressure, may be readily 

 hydrolysed to maltose, which is a crystalloid — non-electrolyte, 

 having a molal O.P. {i.e. belongs to Class 1). Glucose, which 

 similarly has a molal O.P., may be stored in the liver as glycogen — a 

 colloid, which again readily undergoes hydrolysis (to a crystalloid). 

 (See Chap. VIII., ColloidsO 



Further Reading 

 FiNDLAY. '■ Osmotic Pressure." Longmans, Green & Co. 



