588 SCIENCE PROGRESS 



water of crystallisation. The properties of the salt do not, 

 however, correspond satisfactorily with this formula, and since 

 the compound has come into use as a drug its constitution 

 has been revised by Ehrlich & Bertheim. Their results, 

 published in the Berichte der deutschen chemischen Gesellschaft 

 for July 20th, 1907, show that in reality the substance is a 

 salt of para-aminophenylarsinic acid having the following 

 graphical formula — 



NH, 



oas<: oh 



u - As X)Na 



and the commercial product generally contains four molecules 

 of water of crystallisation. By analogy with sulphanilic acid, 

 NH 2 . C 6 H 4 . S0 2 . OH, the free acid has been called arsanilic 

 acid, NH 2 . C 6 H 4 . AsO(OH) 2 , and accordingly atoxyl may be 

 termed sodium arsanilate, NH 2 . C 6 H 4 . AsO(OH)ONa, 4HA 

 In this substance, the arsenic is very tenaciously held by the 

 organic radicle, and is split off only under the influence of 

 fused potash or by the action of hot hydriodic acid. The 

 strength of the connection between the arsenic and phenyl 

 is probably correlated in some way with the therapeutic 

 action of the salt, for it has been found that atoxyl is forty 

 times less poisonous than Fowler's solution. The salt may 

 be applied either internally or externally ; it has been indi- 

 cated in several maladies, among others in tuberculosis and 

 various skin troubles. Of special interest at the present 

 time are the promising results which have attended the use 

 of atoxyl in cases of sleeping sickness. Although it is as 

 yet too soon to claim any specific action for the drug in 

 this or other diseases, yet it is already evident that in this 

 organic arsenic derivative we have a valuable therapeutic 

 agent. 



Although this review of the modern synthetical drugs is 

 unavoidably brief and incomplete, it is hoped that it will 

 serve to throw some light on the chemical nature of these 

 substances many of which are at present in everyday use. 



