38 



The potassium can, however, not he determined quantitatively by 

 titration, from which it appears tiiat we have to do here with an 

 acid that is stronger liian the mono dioi boric acids described. 

 Unclianged pyro cateciiin can again be withdrawn with ether from 

 the aqueous solution. 



The oilier complexes stronger than boric acid are probably also 

 built up according to the type of di-pyro cateciiin boric acid. 



So far, however, the separation of a derivative that probably 

 belongs to this type, has succeeded only in one diol of abiphatic 

 character, i.e. in the cis-cyclo heptane 1.2 dioi. This diol was first 

 prepared by Dkrx from suberic acid; he ascertained that i( increases 

 the conductivity of boric acid in a great degree, and states that he 

 has succeeded in separating a solid boric acid compound, the B-content 



of which agrees with the formula C.H,, ; ,.^BOH.H,0'). As only 



0.2 gramme of this diol were available (prepared by Dkkx), I have 

 carried out the following experiments on micro-chemical scale under 

 the microscope. 



With an almost saturated boric acid solution the diol gives rise 

 to the formation of an oil which is only soluble in much water.') 

 This oil is probably the liquid diciscycloheptanediolboric acid, from 

 which more or less accidentally Dkrx obtained the mono ciscycio 

 heptanediolboric acid as a solid substance. On addition of a little 

 strong potassium hydroxide an aqueous suspension of this oil gives 

 crystals of a potassium salt, w'liile also a drop of aniline is dissolved 

 with se|)aralion of beautiful crystal needles, which are, however, 

 pretty readily soluble in water and other solvents. 



In connection with the small quantity of material available it was 

 better to abandon the idea of an examination of the liquid compound 

 itself, and to try and separate one of the salts. For this purpose I 

 chose the aniline salt to avoid the possibility that with KOH, as 

 with the other cyclic diols, a compound of the monotype would 

 again crystallize out. It might, however, be expected of aniline that 

 it would give a crystallized salt only with a stronger acid. 



Only a few tenths of milligrammes of the aniline salt were 

 obtained in a sufficiently pure condition with a melting-point of 

 about 50°. Mr. H. Gkavestbin was so kind as to take the execution 



1) Proefschria Delft and Recueil 43, 340 (1922). 



"-■) As Mr. Derx communicated to me in a conversalion, this oil was also obser- 

 ved by him, but considered as an impurity. He has obtained the solid boric acid 

 compound described by him in a small quantity from a pretty large quantity of 

 this oil and through rather complicated manipulations. 



