1658 
some resemblance with an a-hydroxy-acid and as these acids cause 
an enormous increase of the conductivity *), the considerable increase 
caused by the fructose is not so strange. 
Moreover, the formation of a comparatively strong fructose-boric 
acid, even at very weak boric acid concentrations is a further proof 
that boron must be considered as an important element in nature’s 
household. 
In consequence of these strongly acid properties and the circum- 
stance that the mutarotation is accelerated by H-ions, great difference 
was found here in the values of the mutarotation-constant determined 
with and without addition of borie acid (with glucose and galactose 
this difference kept within the experimental errors). 
This great difference with the fructose, moreover, corroborated the 
probability of the entire hypothesis, as the constant of the reaction 
at which the «-fructose-boric acid was transformed into the (« + 9) 
fructose-boric acid mixture, agreed with this increased mutarotation 
constant. In order to determine this constant, dilute borie acid solu- 
tions had to be used and the temperature had to be kept low (0°). 
With a molar-a-fructose + 0.44 m. boric acid solution, the con- 
ductivity at O° altered so rapidly that the equilibrium was already 
practically attained after a few minutes. 
A solution of one molecule of fructose in 0.22 mol H,BO, exhibited 
the following change of the specific conductivity (¢ = 0°). 
= 200 £2 ; Cap. resistance v. = 0.1661. Mutarotation 50, fruct. sol. + 0.22 m. H3BO3. 
| oa 
| 3 E | K>< 108 | KK’ = log wee | # | Rot. KER = = log Fe 
a | = Ee 
12 | 559.5 | 658 1.5 3204 | 
16 | 552 678 | 0.0541 | 9.5 | —31.5 0.044 
20 | 548.5 | 687 0.0456 11.5 | —30.9 | 0.040 
25 | 545.5 | 695 0.0442 13.5 | —30.3 0.040 
30 | 544 | 700 0.0405 16.5 | —29.6 0.038 
40 | 543 102 0.0308 19.5 | —29.2 0.041 
oo | 541.5 709 24.5 | —28.5 0.037 
o | —27.5 
The change in the conductivity was still difficult to follow; for 
1) Rec. 35 211 and 313 (1915). 
