110 CHEMICAL EQUILIBRIA 



of observation. The first observed value of ;r obs 

 5-4 is much too high, probably due to the dissociation 

 of the compound of ferrocyanic acid and casein. 

 The close coincidence of the :tr obs with the ;r calc 

 indicates that we really have to do with an adsorption 

 phenomenon. 



In general it is supposed that adsorption pheno- 

 mena play a very important role in biochemical re- 

 actions. Without doubt their existence is proved in 

 many cases, but the predominant influence which is 

 ascribed by the school of colloidal chemistry to these 

 phenomena seems to be greatly over-estimated. 



The equilibria between highly organized products 

 similar to the enzymes, namely the toxins, their anti- 

 bodies and their compounds, have been investigated 

 at some length, because of the extreme importance 

 of these substances in therapy. EIIRLICH was the 

 first to subject the neutralization of toxins to a 

 quantitative study. He was especially interested in 

 the behaviour of diphtheria poison, when it was 

 neutralized by adding antidiphtheric serum. He 

 took a certain quantity of poison containing 100 

 lethal doses, i.e. enough for killing 100 guinea-pigs 

 in between three and four days. He added a 

 quantity A of antidiphtheric serum which was 

 sufficient to neutralize 25 per cent of the poison, so 

 that the mixture contained only 75 lethal doses. 

 He then added the quantity A again, and repeated 

 that a certain number of times, say until 6 A were 

 added. It was in this manner that JULIUS TIIOMSEN 

 investigated the evolution of heat on successive 



