COLLOIDS IN PROTOPLASM 



It marked an important progress in Biology 

 when the views of Thomas Graham were applied to 

 protoplasm. The manifestly colloidal nature of 

 living protoplasm demonstrated ad oculos the 

 significance of studies on colloids for Biology. 

 Protoplasm shows itself as an almost liquid slime 

 of the consistence of a liquid starch-paste or of a 

 strong solution of albumin, and never becomes solid. 

 Graham divided colloids, according to their more 

 liquid or more jelly-like consistence, into Sols and 

 Gels. There is no doubt that protoplasm has the 

 nature of a sol. While the knowledge of salt 

 solutions was being perfected in the 'seventies and 

 'eighties of the last century, colloidal solutions or 

 sols were also extensively studied. So it was 

 learned that colloidal sols differ from salt or true 

 solutions in a number of important points. Salt 

 solutions are always electrolytes, colloidal solutions 

 never are. Salt solutions have a lower freezing- 

 point and a higher boiling-point compared with the 

 medium of solution (water). Colloidal solutions 

 do not show any divergence from the two principal 

 points of temperature of the medium of solution. 

 Modern physical chemistry explains the proper- 

 ties of true solutions by the hypothesis that, 

 depending upon dilution and temperature, a larger 

 or smaller number of the dissolved molecules are 

 split up into smaller particles which are iden- 

 tical with Faraday's Ions. Colloidal solutions 

 do not conduct electric currents and do not show 



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