7 o6 SCIENCE PROGRESS 



Organic Arsenic Derivatives 



In 1865 Bechamp discovered among the products of the 

 interaction of aniline and arsenic acid a compound which he 

 supposed was an anilide of arsenic acid, that is, a substance in 

 which carbon and arsenic are not joined directly but through 

 the intermediary of oxygen. Experiments on animals showed 

 that this compound was much less toxic than the ordinary 

 inorganic compounds of arsenic, and it was found safe to 

 administer forty times as much arsenic in the form of the 

 supposed arsanilide as in potassium arsenite (Fowler's solution). 

 The compound, which was accordingly called atoxyl, came into 

 increasing demand as the result of the discovery that it had 

 considerable germicidal powers and could be used in the treat- 

 ment of sleeping sickness and other diseases of protozoal origin. 



In 1907 Ehrlich and Bertheim showed that atoxyl was a 

 true organo-metalloidal compound, the arsenic being directly 

 attached to carbon. The compound therefore furnishes another 

 striking example of the masked or hidden state of metals and 

 metalloids in their organic derivatives, this intimate state of 

 combination with carbon leading to a modification in the 

 analytical and physiological reactions of these elements. 



Although destroying trypanosomes in vivo, atoxyl has no 

 effect on these organisms in vitro. A preliminary change, which 

 takes place in the tissues of the host, appears to be necessary 

 before the drug becomes effective. The arsenic in atoxyl (I.) is 

 in the same saturated quinquevalent condition as it was in 

 Bunsen's non-poisonous cacodylic acid (II.) 



v. v. 



NH 2 .C 6 H 4 . AsO(OH) 2 (CH 3 ) 2 AsO . OH. 



1. 11. 



The substance which actually destroys the trypanosomes 

 in the body of the host is in all probability a compound of 

 tervalent arsenic. Following up this hypothesis, Ehrlich after 

 many trials ultimately arrived at the compound, salvarsan 

 (III.), or "606," this number indicating the series of substances 

 which had been examined before success was attained : 

 OH OH OH OH 



HCl.NHg^ r^NHs, HC1 NHjf^ ^jNH . CH 2 . S0 2 Na 



As = As As = As 



in. IV. 



