232 Dr. A. W. Hofmann on the Phosphorus Bases. [Mar. 21, 



Cahours and myself; this body is no longer capable of forming saline com- 

 pounds. We thus arrive at the following series : — 



H 3 P + 4 = H,P0 4 . 

 (CH 3 )H 2 P+0 3 ==(CH 3 )H 2 P0 3 . 

 (CH 3 ) 2 H P+0 2 =(CH 3 ) 3 H P0 2 . 

 (CH 3 ) 3 P+0=(CH 3 ) 3 PO. 



By examining this series it is observed at once that all the bodies here 

 described are derived from phosphoric acid, the oxides generated from the 

 methylated phosphines being orthophosphoric acid, the hydroxylic groups 

 of which are successively replaced by methyl. 



HO ] 



Orthophosphoric acid HO \ PO. 



HO J 



CH 3 



Methylphosphinic acid HO I PO. 



HO J 



Dimethvlphosphinic acid CH 3 y PO. 



HO J 



CH 3 1 



Trimethylphosphine oxide CH 3 I PO. 



CH 3 J 



This symmetrically constituted series does not stand alone ; indeed 

 orthoarsenic acid forms the starting-point of a perfectly analogous group of 

 compounds, which are obtained, however, by processes different from those 

 yielding the phosphorus bodies. The substance corresponding to methyl- 

 phosphinic acid is arsenmonomethylic acid, discovered by M. Baeyer ; 

 that analogous to dimethylphosphinic acid is the well-known kakodylic acid 

 of M. Bunsen ; finally, trimethylarsine oxide has been obtained by M. 

 Cahours when submitting trimethylarsine to the action of oxidizing agents. 



HO 1 



Orthoarsenic acid HO I AsO. 



HO J 



CH 3 ] 



Arsenmonomethylic acid HO I AsO. 



(Methylarsinic acid) HO J 



CH 3 | 



Kakodylic acid CH 3 ]■ AsO. 



(Dimethylarsinic acid) HO j 



CH 3 ] 



Trimethylarsine oxide CH 3 1 AsO. 



CH„ I 



The formaticn of nefhyl- and dimethylphosphinic acid is thus seen to 

 illustrate again the unmistakable analogy of the two elements, phosphorus 



