39 



of a micro-elementaiT analysis upon him. The combustion of liiis 

 boron-containing conmponnd requires, iiowever, special preliminary 

 experiments, and lias not yet been accomplished; the results will 

 be |)nblished later. A determination of the boron-content yielded 

 the following results: 9,76 ragr. were dissolved with 1 gr. of pure 

 mannite in 10 cc. of water, and titrated with 0,0097 N barite water 

 (under similar circumstances tested by pure boric acid) and phenol- 

 ftalein as indicator. Consumed 2,60 cc. Calculated for C^Hj^O^NB 

 . . . 2,99% B; found 2,8 '/„ B. 



To all probability we have here actually to do with diciscyclo- 

 heptane diol boric acid aniline. 



In this compound the aniline is bound slill more loosely than in 

 aniline dipyro cntechin boric acid. In vacuum at room temperature 

 it already escapes, the remaining part becoming liquid. The liquid 

 residue becomes solid again by the addition of aniline. Also on 

 evaporation of the aqueous .solution over concentrated sulphuric acid 

 an oil remains behind, which becomes solid again by the addition 

 of aniline. Beside a dish with pumice saturated with aniline the 

 salt can, however, be regained unchanged by evaporation of the 

 aqueous solution in vacuum. 



Di-ciscycloheptanediol-boric acid is, therefore probably a much 

 weaker acid than dipyrocalechin-boric acid, and the great increase 

 of conductivity of boric acid by pyro-catechin must, therefore, be put 

 to the account not only of the favourable orientation of the OH-groups, 

 but also partially to the account of the acidifying intluence of pyro- 

 catechin as such. This admonishes to caution in making comparisons 

 with regard to the orientation of the HO-groups between diols that 

 are not very much a like in structure, exclusively on the ground of 

 measurements of the conductivity. This point was, indeed, already 

 foreseen by Böeseken, and was a.o. mentioned by van Loon ') and 



LlEMPT '). 



That also the increase of conductivity caused by the «-oxy acids 

 in the boric acid is probably to be attributed to the formation of 

 complex acids built in an analogous way, we have been able to 

 make plausible by showing that the analyses of the Scheibe's boro 

 dicitric acid potassium') and of the zincous salt of Jahns' boro di- 

 salicylic acid are in agreement with the formulae: 



•) Proefschrift Delft, p. 56. 



-) Recueil 39, 359. 



') Also the free acid has been separated crystalline by Scheibe and by me. It 

 is, however, difficult to purify and dry. Scheibe's analysis, which 1 have not yet 

 checked, is in harmony with my view. 



