102 



ASYMMETRIC ANALYSIS 



C 500 



(U 



E 



'*- 3 



_c 



^ 2.5 



6) 

 o 



2 



010% 



02 0% 



CONC. 



10 lb 20 25 



Log. of effective concentration i.v-ii) 

 Fig. 11. Killing action of the optical isomers of nicotine on the fish 

 Lencisciis idiis. The lower graph represents the toxicity curves in 

 logarithmic coordinates. (From Cause and Smaragdova, 1939.) 



According to the principles of quantitative toxicology, 

 concentration-toxicity curves can usually be expressed 

 by the empirical equation of Ostwald : 



k 



^' ^ (x-n) ™ 

 where u is the killing time, x the concentration of the 

 poison, n its minimal lethal concentration, and k and m 

 are constants. The constant m shows how rapidly the 

 toxicity increases with the concentration; it thus charac- 

 terizes the dynamics of the killing process. If one plots 

 log y on ordinates and log {x-n) on abscissae, the relation 

 between these variables will be represented by a straight 

 line. The slope of this straight line is measured by the 

 constant m. 



