It is not improbable that the mobile hydroxyl-group receives some 
support from the side of the furane-oxygen atom say in the sense 
that to this O-atom is still bound a molecule of water so that the 
number of hydroxyl groups is greater here and the chance for 
the fixing of boric acid is more favourable *). 
In the non-reducing sugars and in the glucosides the furane-oxygen 
atom is present, but the mobile OH-group has disappeared, so that 
here the cause of the boric acid combination is cancelled. 
If the explanation of this favourable influence of the furane-oxygen 
atom is correct, the fructose [in which the circumstances are still 
more favourable, because to the C-atom that carries the furane-oxygen 
H OH Fig. 2 
Cad CH, OM CH, OM on 
fB —- rrucTtosEsS — @ 
Fig. 2. 
and the mobile OH-group (Fig. 2) are still attached ¢vo other OH- 
containing groups | will have to cause a much more powerful 
exaltation in the conductivity than the two investigated aldoses. 
This, indeed has now been proved to be correct. 
For the increase in conductivity of the equilibrium mixtures of 
the glucoses, galactoses and fructoses were found the following figures 
(T = 25°; the tructoses at O° to 3°). 
Mol. (@ and glucose + 0.5 mol. H,BO, 95 << 10s Ke Hb: 
8 AOR EG ae 
_ +0405. A os) eee MR eee 
0.5 mol.(«and 3) galactose + 0.5 2 ae 25x ,, 3 
mol. (@ and 3) fructose + 0.44 „ Ee 99 
ze 022 ,, 1000) Pe Be 
a + 0.11 De ete) re = 
. 450,02 ol VO ae 
Although a considerable exaltation in conductivity, as indicated 
above, might well be expected the amount of it was strikingly large. 
On closer examination of the fructose molecule we notice, however, 
1) E. F. ARMsTRONG (Die einfachen Zuckerarten und die Glucosiden” pag. 22— 
27) calls the oxygen atom of the furane-ring, when taking up one molecule 
water, quadrivalent and thus considers the sugar hydrates as oxonium compounds, 
