168 TKANSACTIONS OF SECTION B. 



WEDNESDAY, SEPTEMBER 10. 

 The following Papers were read : — 



1. Metallurgy during the War. By Professor C. H. Desch, D.Sc. 



2. Glass Manufacture at the end of the War. By Dr. M. W. Tea vers. 



3. The Recovery of Nitre and Pitch from Smolce Candles. By Major 



E. E. Thomas. 



4. Geochemistry and the War. By Professor P. G. H. Bos well. 



5. Equilibrium, in the System NaNO,—NH^Cl—NaCl—NH^NO,. 

 By Dr. T. M. Lowry, F.R.S., and Dr. E. P. Perman. 



THURSDAY, SEPTEMBER 11. 

 The following Papers were read : — 



1. hid.ustrial Bacteriology. By Dr. C. A. Thaysen.^ 



2. The Mechanism of the ' n-Butyl Alcohol and Acetone ' Fermentation 



Process. 

 By Joseph Eeilly, M.A., D.Sc, and Wilfred J. Hickinbottom. 



Among the more recent applications of bacteriology to technical processes 

 is the conversion of carbohydrates into a mixture of w-butyl alcohol and acetone 

 (A. Fernbach and E. Strange, E. P. 21073, 1913). Certain bacteria are known, 

 as, for example, granulohacter hutyliciim, bacillus amylobacter , and the butylic 

 bacillus of Fitz, ti/rothrix tenuis, which, under certain conditions, convert carbo- 

 hydrates mainly into n-butyl alcohol and acetone, producing, in addition, carbon 

 dioxide and hydrogen, together with small quantities of acids and other 

 alcohols (chiefly ethyl). From 100 grams of maize may be produced V grams 

 of acetone, 16 grams of ti -butyl alcohol, 2 grams of volatile fatty acids, 19 litres 

 of carbon dioxide, and 16 litres of hydrogen at 20°. 



In a normal fermentation, which usually lasts about 24-30 hours, the acidity 

 of the masb gradually increases from a very small value until 10 c.c. of the 

 mash liquor requires from 3.5 to 4.5 c.c. of 0.1 A'^-sodium hydroxide solution 

 for neutralisation, after eliminating carbon dioxide. Usually 13 to 17 hours 

 are required before the acidity reaches its maximum value, when the formation 

 of acetone and 7!-butyl alcohol commences. The actual value for the maximum 

 acidity and the interval before the «-butyl alcohol and acetone are formed, 

 depends to some extent on the experimental conditions, the source of carbo- 

 hydrate, and the percentage of inoculant. During the pro.duction of acetone 

 and n-butyl alcohol in the mash, the acidity falls gradually to a constant 

 value of about 1.5-2.5 c.c. of 0.1 A^-sodium hydroxide per 10 c.c. of maeh. 

 It was considered that, in view of these variations, a study of the acid-forma- 

 tion in the fermenting mash might give an insight into the fermentation pro- 

 cess. 



The acids present in the mash are principally acetio and butyric acide 

 with a small quantity of a non-volatile acid. It is found that the ratio of these 

 acids to each other depends on the age of the fermentation. Shortly after 

 inoculating, the acids are present in the proportions of approximately 4 or 5 

 molecules of acetic acid to one of butyric acid, but as the acidity increases, the 

 ratio of acetic acid to butyric falls, until at the period of maximum acidity 

 there are about 1.1 to 1.4 molecular proportions of butyric acid to one of 



' To be published in Jovrn. Inst, of Brewing. 



