98 



cal eflfects different from those of the dinitrophenol which is more 

 water soluble. 



2,4-DICHLOROPHENOL 



Clowes and Krahi found that 2,4-dichlorophenol produces 

 effects in Arbacia eggs similar to those induced by 2,4-dinitro- 

 phenol, which is to say that both produced an increased oxygen 

 uptake in a low concentration, and decreased O2 uptake at a higher 

 one with a complete inhibition of cell division. This suggests an 

 action mechanism similar to that of the nitrophenols. However, 

 the experiment in vHro shows that while the dichlorophenol has 

 a strong quenching action on the phosphorescence of riboflavine 

 even in 10"' Af, its action is less specific and it affects the excita- 

 tional states of other substances as well on which the nitrophenol 

 had no appreciable action. So, for instance, it was found to quench 

 the yellow phosphorescence of acridine (saturated water solution) 

 in a lO"* M concentration. The dichlorophenol can thus be ex- 

 pected to suppress oxidative phosphorylation but can also be ex- 

 pected, at the same time, to inhibit other processes. The experi- 

 ments of M. Middlebrook bore out this expectation. Her results 

 (Fig. 24) showed that the dichlorophenol, similarly to the dinitro- 

 phenol, completely inhibits oxidative phosphorylation in a low 

 concentration, but at the same time it cuts down oxygen uptake 

 so that in this case the failure of phosphorylation might also have 

 been secondary to the failure of oxidation. 



Salicylic acid has also been shown recently to be a powerful 

 metabolic stimulant (Alexander and Johnson) and to uncouple 

 oxidative phosphor}4ation in a 5 X 1^"^ ^ concentration (Smith 

 and Jeffrey). One gram, the medical dose, taken by an adult cor- 

 responds to a random concentration of 10'* Af. Salicylic acid 

 quenches the phosphorescence of riboflavine in a 10~' Af dilution. 



