CHEMICAL PHENOMENA IN LIFE 



pension. We must therefore ask what character- 

 istics are found in these suspensions. Such 

 systems have in general the properties of the 

 liquid medium. The specific weight, viscosity, 

 and surface tension do not differ from the value 

 found for the medium, and so it is with regard 

 to the freezing-point, the boiling-point, and the 

 power of conducting electric currents. We may 

 understand this to be due to the comparatively 

 small quantity of the suspended substance in 

 proportion to the quantity of the liquid medium. 

 Such suspension systems do not in any way re- 

 semble solutions. Here we may mention the so- 

 called phenomenon of Cataphorcsis in these 

 suspensions. When an electric current passes 

 through the suspension, the particles migrate to 

 the anode or to the cathode, corresponding to the 

 specific character of the suspension. This pheno- 

 menon, which has been thoroughly discussed by 

 physical chemists, has not yet shown itself to be 

 of any great importance for the chemistry of 

 protoplasm. 



Whilst suspensions with comparatively large 

 particles can be recognised as suspensions by 

 ordinary microscopical observation, the particles 

 in other colloidal solutions can be discovered only 

 by means of the ultramicroscope. We have 

 mentioned that protoplasm contains ultramicro- 

 scopic particles or submicrons, which are not seen 

 but by ultramicroscopic investigation. All these 

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