PHYSIOLOGICAL EFFECTS OF HYDROGEN CYANIDE. 



373 



It is obvious from the foregoing discussion that hydrogen cya- 

 nide penetrates living membranes chiefly in the form of molecules 

 and in this respect is similar to other weak acids. Jacobs (i8a) 

 showed that carbonic acid killed various species of protozoa in a 

 different order than mineral acids, which act primarily through 

 their H ion (Collett, 23). This indicated to Jacobs, that the 

 physiological effect of CO 2 was due to the entrance of the molecule. 

 Beerman (24) and Bodine (25) obtained similar results with H 2 S 

 and HCN respectively. More recently, Osterhout (96) and 

 Osterhout and Dorcas (9^) showed by direct analysis that hydro- 

 gen sulfide and carbonic acid penetrated the living cells of Valonia 

 chiefly in the form of molecules and not as ions. Brooks (210.) 

 found that the amount of 2 6 dibromo phenol indophenol in 

 the sap of Valonia was proportional to the amount of undissoci- 

 ated dye in the external solution. 



EFFECT OF TEMPERATURE. 



A series of experiments was conducted to determine the effect 

 of temperature on the permeability of frog skin to hydrogen cya- 

 nide. The results are plotted in Fig. 6. It is evident from these 

 curves that the higher the temperature the greater is the concen- 

 tration of intracellular cyanide at any stated time. The curve 

 suggests that of a typical unimolecular reaction as can be easily 

 demonstrated by calculating the velocity constant from the fol- 

 lowing equation : 



K=i/t log a/ax (26) in which x--i\\e. amount of cyanide 

 in the cell at any time t; a ==the amount of cyanide in the cell at 

 equilibrium (Table I.). 



TABLE I. 

 VELOCITY CONSTANT K CALCULATED FROM THE UNIMOLECULAR EQUATION 



K = LOG- AT VARIOUS TEMPERATURES. 

 t a-.v 



External and internal pH 6.8. 



