448 



SCIENCE 



[N. S. Vol. XXXIX. No. 1004 



No. 13 



NHj 



! ! I 



N = N: 



I I i 



:><:>» = 



NHz 



SOsNa 



\. 



CH; 



>N = N 



I I 



No. 15 



NH2 



I I 



NaOaS SOjNa 



No. 16 



NH2 _ NH2 



/\/\n=n^~\/"\n=n/\/N 



NH2 

 CH:, CHs I I I 



SOsNa 



Both of the naphtylamine disulfonic acids 

 with which we have worked have yielded 

 equally brilliant results (the 2.3.6 and 1.4.8 

 ones) . 

 No. 236 



N = n/^N^\n = N 

 / >NH2 CHs CHs H^N/ V 



No. 148 



SOsNa 



SOsNa 



NH2 SOsNa 



>N=N- 



■ I I 



NaOsS NH2 



/YY=N<_x_> 



II CHs CHs I I I 



\/\/ \/\/ 



SOsNa NaOsS 



We meet, however, among the naphtyla- 

 mines surprises which are just as remark- 

 able as those which greeted us in the naph- 



tol group, for the isomeric dyes which are 

 listed below (12, 14, 17, 18 and 25) are all 

 negative. 



No. 12 



NHj NHs 



>N=N 



N=N< 



CHs CHs 



No. 14 



NHj _ _ NH2 



III CHs CHs I I I 



No. 17 

 NaOsSf 



SOsNa 

 NH2 



/\n=n/'\/"\ 



I I CHs 



NaOsS 



NH2 



No. 18 

 NaOsS NH2 



N = Nr Y jSOsNa 

 CHs CHs I i 



I I 



I I 



N = n/ N/ ^N = N 

 NH2 CHs ~CH3 H2N; 



We shall not have to insist that it is 

 hardly likely that chemical reaction be- 

 tween these dyes and substances with 

 which they could truly combine would 

 hardly occur or fail to occur in this capri- 

 cious way. Our results then are hardly 

 capable of being formulated in terms of 

 the chemoceptor theory, for there is no one 

 chemical configuration which we are able to 

 pick as a chemoceptor. Our search at this 

 juncture for some common characteristic 

 possessed by a positive in contrast to nega- 

 tive dye, a characteristic which when pos- 

 sessed always permitted the dye to be a vital 

 stain and when absent led us to predict its 

 failure, was rewarded with success. We 

 were in short induced to look into the phys- 



