.')N 



often I)osl when lie used \v;i1(M" willioiil s;ills or else wafei' 

 with salts in excess 



1 (ricd siiiiilnr aiT;m<,U'meiits as lliinlooii -'«7j jos) 

 Fi'esh emhrvoiiie lissiie juice was mixed with 10 |)ei' cent 

 blood coal and a hidler soliilion which ^axc llie inixliiri' such 

 a hydro<»en ion concentration by wliicli we enipiricaiJN' found 

 that a maximal adsorption of growth |)rom;)lin<f sui)stances 

 took jilace. Alter one hour at 39 il. and 12 hoiu's in the 

 relrij«t'ralor. the blood coal was separated from the fluid by 

 centrifuginj^. After the supernalani fluid had been removed, 

 various solutions such as destilled water. Rin<fer solution, 

 10 per cent saccharose solution, were added to the (ufferent 

 tubes with blood coal. The coal was shaken u|) and some of 

 the lubes were placed at 53 ('.. foi- two hours, some at 39 ° C 

 and some directly placed in the refrigerator, where they 

 all were ke])t foi' aboid 15 honi's. Al the end of this time, 

 the supei'natant fluid was drawn off and added to the cul- 

 tures and the rate of growth determined. The adsorption 

 was controlled chemically by also determining the amoinits 

 of nitrogenous substances adsorbed and dissociated by the 

 various methods. 



It is generally known, that highly surface active substan- 

 ces can displace certain adsorbed substances from the adsor- 

 bent. Rona and Tosh ^^^) found that elhyl-urethane was 

 able to displace the adsorbed substances. An attempt with 

 ethyl-urethane was therefore made to displace the adsorbed 

 grow^th promoting substances. Some preliminary experiments 

 were made to investigate the displacing power of various 

 surface active substances. At the same tinu' these substances 

 w^ere tried in the cultures in the concentrations where a good 

 displacing effect was obtained. 



In these ])reliminary experiments on displacement by 

 surface active substances, bh)od coal was used as adsorbent 

 and a 0,3 per cent solution of methylene blue in water as 

 adsorbendum. After the adsorption had taken place, the solu- 

 tion wa.^. sej^araled from the blood coal and the latler washed 



