59 



until the water remained colourless. Water was then added 

 until the original volume as before was established. The 

 displacing agent was then added to the tubes in different 

 concentrations and the blood coal stirred up. The colour of 

 the water could then be measured colourimetrically at the 

 same time as the surface tension could be determined. — The 

 experiment in table (i shows that the lowering of the surface 

 tension about 8—9 dynes results in a displacement of methy- 

 lene blue from the adsorbent, when 95 per cent alcohol is 

 used as displacing agent. 



Table 6. 



Showing ttie effect of some surface active substances on adsorbed 



mettiylene blue. 



Of course it cannot be concluded from this experiment, 

 that other substances, as for instance the growth promoting 

 substances from the embryonic tissue juice, can be displa- 

 ced from the adsorbent in the same way by lowering the 

 surface tension to the same degree which was able to dis- 

 place the methylene blue. This depends upon several fac- 

 tors, the solubility of the adsorbed substances in the dis- 

 placing agent and the surface energy of the adsorbed substan- 

 ces in relation to the surface energy of the displacing agent. 

 Ethyl-urethane was able only to lower the surface tension of 

 Ringer solution, when present in a rather high concen- 

 tration. 



The concentrations of sodium oleate and ethyl-urethane 

 by which they were able to displace methylene blue from 



