1911.] Acetylmethylcarbinol and 2.3-Butylene Glycol. 495 



A small amount is held in the dry residue after distillation, and must be 

 extracted with dry ether, and the glycol thus obtained, after evaporation of 

 the ether, added to the distillate. 



The estimation depends on the fact that the glycol is readily oxidised by 

 bromine under the influence of light to diacetyl, which can be estimated 

 by its reducing power. Any acetylmethylcarbinol present is quantitatively 

 oxidised to diacetyl in this way, but as the quantity of this substance will 

 already have been determined, the amount of diacetyl formed from it is 

 known, and the difference between this and the total diacetyl represents 

 that due to the glycol. The details of the process are as follows : — An 

 aliquot portion of the distillate is treated with a small quantity of bromine 

 (0-1 c.c. for the distillate from the fermentation of 5 grm. of substance), and 

 left exposed for 12 to 15 hours to the light of a 50-candle-power electric 

 lamp. A further addition of bromine is made if the solution becomes 

 completely decolorised, and the exposure continued. Any free bromine is 

 then removed by the cautious addition of sulphurous acid, excess of this 

 being carefully avoided. The solution is next saturated with sodium chloride, 

 and the diacetyl distilled off and estimated by determining the reducing 

 power of the distillate. 



The results obtained by the above method are low, as the oxidation of 

 the glycol to diacetyl is not quantitative. Control experiments with known 

 amounts of glycol show that the actual results obtained are two-thirds 

 the correct value, and a correction for this has been made in the tables 

 given below. 



In most cases the diacetyl produced by the oxidation was further charac- 

 terised by the preparation and analysis of the phenylosazone. 

 Two typical analyses gave the following results: — 



1. Substance fermented — galactose. Organism — B. cloacae.. Osazone — 



m.p. 243° C. 



0-2109 grm. gave 39'4 c.c. N at 23-5° C. and 765 mm. N = 2114 per cent. 



2. Substance fermented — arabinose. Organism — B. lactis aerogenes. Osa- 



zone — m.p. 244° C. 

 0-1349 grm. gave 25 c.c. 1ST at 22° C. and 765 mm. N = 21-13 per cent. 

 Diacetylphenylosazone, C 16 Hi8N 4 , requires N = 21-05 per cent. 



In the sugar experiments the amount unfermented was estimated in the 

 residue left after the extraction of the glycol by dissolving it in water, 

 making up to a known volume, and determining the reducing power after 

 treatment with mercuric nitrate (Patein). 



