Chemistry. — "The Valency of Boron". Bj Prof. J. Böeseken. 

 (Communicated at the meeting of December 80, 1922). 



As the complex organic boric acid compounds have gradually 

 acquired a great signiticance fur the determination of the compo- 

 sition of a number of organic compounds and for the knowledge of 

 the configuration and of the state of motion of tiie molecules in 

 space, it was felt as a serious deticieucy that the existence of these 

 complex compounds had so far been exclusively derived by an 

 indirect vva^', and that no compound had as yet been separated, the 

 composition of which had been entirely made clear. 



Some years ago we had, indeed, succeeded '1 in olitaiuing some 

 well crystallized salts of pyrocalecliol boric acid, but tliey seemed 

 to be built up in such a complicated way that no accurate conception 

 could lie formed of their composition. 



Now it chanced that Mr. Hkrmans '), who was engaged in an 

 investigation of tlie ecpiilibria in the system glycol -|- acetone ^ 

 glycol acetone -|- H,0, and also examined the behaviour of the 

 glycols towards boric acid, obtained a compound that crystallized 

 beautifully from tetia-methyl-propane-diol-1.3 and boric acid, 

 which according to analysis and properties possessed the following 

 cyclic composition : 



(CH.).C^O 



/ \ 

 CH, B— OH. 



\ / 

 (CH.).C-O 



Against our expectation this compound, which had a delicate 

 saifron odour, was hardly acid, at any late less acid than boric acid 

 itself, as a solution of this substance had a smaller conductivity, 

 while it could be ascertained by determinations of the freezing-point 

 that it had not entirely split up into its components in aqueous 

 solutions. 



The discover}' of this compound made a renewed investigation of 

 the boro-pyro-catechates necessary. 



') Recueil 37, 184 (1917). 



') Cf. These Proc. foUowng communication. 



Proceedings Royal Acad. Amsterdam. Vol. XXVI. 



