37 



OX}- derivatives witli "favourably" orientated OH-gioiips, l)elong to 

 another group. In 19J7 Böesekkn (in ooiiaboratioii witli Obkhkn and 

 Miss VAN Hakftkn, Recueii 37, 184) described several salts of pjro 

 catechin boric acids of pretty complicated constitution. As (lie former 

 had already for some time considered (he analysis vakies found to 

 be uncertain, and as the boric acid compounds described above 

 appeared to be by no means [)articularly complex, there was snfli- 

 cient occasion to subject the l)eautifully crystallized salts of pyro 

 catechin boric acid to a renewed investigation, the more so because 

 pyro-catechin greatly increases the conductivity of boric acid, so that 

 accordingly the other type of compounds might be expected iiere. 

 This expectation was confirmed : the potassium salt appeared to 

 possess the forumla Cj^HjO^BK '). 



The carbon was determined by the wet way according to the 

 method of Meisknheimer, the hydrogen according to a simplified 

 method worked out by myself, about which more will be given 

 later. The following values were found : 



C 54,28; 54,26 H 3,03 B 4,3 K 14,7 

 Calculated 54,14 3,00 4,1 14,7 



The only plausible structure that answers to this is: 



^^B<^^ j (potassium dipyrocatech in borate) 



K 



The boron is hei'e pentavalent, or has (according to Werner's 

 nomenclature) the coordination value four, just as in the w^ell-known 

 compounds KBF, and Na[B(OC,H5(4j. The latter was obtained from 

 NaOCjH^ and boric acid triethyl ester ^). 



The free dipyro catechin boric acid can be obtained by heating 

 the anilin salt in a vacuum of some mm. Hg. at 100 — 120°, in wliicli 

 the aniline escapes quantitatively. Mr. Meulenhoee (who has under- 

 taken a closer investigation of these derivatives at Prof. Böeseken's 

 request), found that the acid obtained in this way can be prepared 

 in perfectly pure condition by sublimation in vacuum at about 200°. 



The potassium salt described is very little soluble in cold water, 

 and this solution gives an alkaline reaction, probably in consequence 

 of the fact that a dissociation in pyrocatechin and potassinmborate 

 (possibly first in pyro catechin and niouo-pyro catechin borate) sets in. 



'i The erroneous constitution, given in the last-mentioned paper is owing, partly 

 to an error of calculation that has crept in, partly lo the fact that substances con- 

 taining boron and being rich in G, are not easily combustible. 



2) GopEAU C.r. 127, 721 (1898) e.g. Livio Cambi, Acad, dei l.incei Rend (5), 

 23a, p. 244. 



