Decembeb 9, 1910] 



SCIENCE 



815 



N=N- 



_/\ SOsNa- 



I 



Cl- 



OH NHj 



OH NHj 



I I 



N=N i^'^l'^^l 



SOgNa— I 1 J— SOjNa 



(2) Acid combination liquid: 

 NH, OH 



CI— I 



N=N 



/\ SOjNa- 



Jv/'n 



I 



Cl- 



NH, OH 



I I 



SO.Na— L X J— SOsjSTa 



\/ 



Paradiamidodiphenyl-urea : 



NH. 



— / \— NH-CO— NH— / V 



Best color against sleeping sickness: 

 OH NHj 



I I 



■NT-r^ -NT ./\ 



As far as it is possible to draw general 

 conclusions from this mass of material and 

 the results of countless investigations, Ehr- 



-SOsNa lich established the rule that the effective 



substance must be tetrazo colors derived 

 from naphthalene disulfo acids, with the 

 sulfo groups in the 3.6 position. Mesnil 

 and Nicolle determined that the effective 

 substances must be naphthalene combina- 

 tions. They must contain at least one 

 amido group and two sulfo groups. Con- 

 cerning diamines, it was found that dichlo- 

 rinated substances were the best, and that 

 those amines in which the benzol groups 

 are connected by a two valent group 

 (— NH — CO— NH— ) were most ac- 



-SOsNa tive. The most suitable colors were those 



which dyed the animal body intensely, and 

 it was shown that these were also very 

 good cotton dyes. Altogether, symmetrical 

 colors gave the best results and were less 

 injurious to the health of the animals. 

 Most of the symmetrical colors were abso- 

 lutely harmless when given in such massive 

 doses as 1 gm. for 15 to 20 gm. body weight 

 of mice. 



Concerning the chemistry of atoxyl, it 

 -NH, may be mentioned that it is obtained by 

 heating arsenate of anilin and treating the 

 acid solution with alkali. 

 Arsenic Acid: 



SO.Na— 



\/\/ 



\/ 



I 

 NH 



I 

 CO 



NH 

 I 



N=N- 



OH NU, 



I I 



SO, 



,Na-l^v^-SO,Na 



O=As^0H 

 \0H 



Arsenate of Anilin: 



/OH 

 0=As^0H 



\0H • CeHsNH, 



Atoxyl (P. amidophenyl arsinic acid) 

 NH, 



A 



T /ONa 

 A8=0 

 \0H 



Acetyl-Atoxyl : 



