34 



iilthough various species of fish^, which no vioubt had different 

 tolerances, v/ere UL^ed m obtainini, the above results, some 

 generalized conclusions can be reached concerning relative toxicity 

 of di- and tetrachlorocatechol, Dichlorocatechol, it will be 

 recalled, was acutely toxic in the 2.C to 2,7 ppm range while 

 tetrachlorocatechol was acutely toxic at C,26 to 1.3 ppm. When 

 compared with toxicities of the several substances cited above it 

 is seen that chlormateu catechols v/ere rauch less toxic than the 

 insecticide Dieldrin. Gn the other hand, the chlorinated catechols 

 were more toxic than phenol and catechol. These comparisons have 

 indicated that tlie chlorinated catechols had toxic strengths similar 

 to those of the chlorinated phenols: di-, tetra- arid pentachlorophenol. 

 Chlorinated phenols have been responsible for destruction of fish life 

 in the past. Chlorlnatec. catechols are potentially as dangerous. 



Although comparisons indicated that toxicities of chlorinated 

 catechols and phenols were similar, there were small differences due 

 to chlorine and hydrox^J-l substitution which are worthy of discussion. 

 Toxicity in increasing order of the compounds tested was 

 dichlorocatecliol, dichlorophenol, tetrachlorocatechol and 

 tetrachlorophenol. This order indicates that toxicity increased as 

 number of chlorine atoms on the molecule increased. Conversely, 

 toxicity declined as hydroxyl substitution increaseu from one to two 

 (e.g., tetrachlorocatechol less toxic than tetrachlorophenol). 

 However, decrease in toxicity caused by increasing number of hydroxyl 

 groups from one to two on the molecule was more than overcome by 

 increasing chlorine atoms from tv;o to four (e.g., tetrachlorocatechol 

 more toxic than dichlorophenol) . The results agree with general 

 observations by Sexton (1953) reported earlier and reemphasize the 

 significant role that chlorine substitution plays in increasing 

 toxicity of a molecule. 



