1910. | B. lactis aérogenes on Glucose and Mannitol. 281 
yielded diacetyl by oxidation with bromine in the light and was therefore the 
diphenylurethane of a 2: 3-butanediol. 
Recovery of 2:3 Butanediol from Purified Diphenylurethane, melting at 
Gi ue USE. 
(1) A quantity of the inactive purified diphenylurethane of 2:3 butanediol 
of melting point 197° to 198° (p. 278) was boiled up with alcoholic caustic 
potash until a small quantity gave no precipitate with excess of water. 
Carbon dioxide was then passed in to saturation, the solution evaporated to 
dryness im vacuo, and the glycol dissolved out in alcohol. The alcoholic 
solution on distillation gave a yellow oily liquid. This remained yellow on 
redistilling several times, ultimately, however, by repeated boiling with 
animal charcoal it was obtained colourless. Twocombustions of this substance 
were made— 
I. 0°2449 orm. gave 04746 grm. CO2 and 02396 erm. H,20. 
II. 03592 grm. ,, 0°6945 grm. CO: and 0:3550 germ. H20. 
| Found. | 
| Fe ar | Calculated for C,H, O.. | 
| il | 1B i | 
—— ] 
C ae 52°85 52°75 | 53°33 | 
I erat cone 10 ‘87 10°99 | 11 | 
The boiling point (uncorr.) at atmospheric pressure was 180° to 181°. 
(2) In a second preparation 2°35 grms. were recovered from 14 grms. of 
diurethane. 
Found. 
1 "52: 
0:2322 grm. gave 0°4497 erm. CO, and 0:2298 grm. H.O ie ert ene 
This glycol showed a very faint but just recognisable positive rotation. 
(3) A sample of diphenylurethane (melting point 199°) had been many 
times recrystallised with great care until in the mother liquors, when 
brought to maximum concentration, no optical activity could be observed. 
Of this 29°1 grm. were hydrolysed as before. 41 grm. of 2:3-butanediol 
were obtained. The value of [«]p in 10 per cent. dry ether solution was 
demonstrated to be less than +0°08 and it was considered that this material 
was the inactive substance corresponding to the formula— 
CH3.CH(OH).CH(OH).CHs. 
At ordinary temperatures it exists as a hard white mass. 
0:2432 grm. gave 0°4691 erm. CO2 and 0°:2424 grm. H20. 
