258 



same obtains here I have myself proved in the Laboratory. Some extent 

 of the damage done may be inferred from the following figures which 

 are taken from Maerckers Handbuch der Spiritus fabrikation (Handbook 

 of Spirit Manufacture) p. 461. 



Butyric Acid per cent, in 

 Fermenting liquor. 



0.00 

 0,01 

 0.05 

 0.10 

 0.50 



Vol. per cent. Alcohol formed during 

 the fermentation. 



6.01 

 6.21 

 6.42 

 0.56 

 0.00 



It will be seen that up to t Jq of 1 °/o the amount of alcohol formed 

 is slightly increased from the case in which no butyric acid is present, 

 in this case the increase in the amount of alcohol amounts to | of 

 1 °/o, but when the butyric acid present amounts to something between 

 and of 1 ^ the production of alcohol is nil for practical 

 purposes. It will be noticed that these figures refer only to the 

 influence on the yeast of the life products of the bacteria, but 

 there is a special influence exercised by the bacteria themselves 

 irrespective of the various acids which they produce. It is not 

 the place here to enter into a discussion on this point, it is mentioned 

 only to shew that the evil could not be remedied by neutralizing any 

 excess of acidity which might be produced. Taking into account then 

 the influence exercised by bacteria and their products, it is easy to under- 

 stand that if we depend upon the trash cistern to furnish us with a 

 supply of vigorous yeast to produce a fairly rapid and satisfactory at- 

 tenuation, we shall be disappointed. The yeast will have been already 

 weakened in its fermentative and reproductive capacities, and conse- 

 quently the fermentation will be slow, that is to say the rate of attenu- 

 ation and the yield of alcohol will be unsatisfactory. I am fully aware 

 that trash cisterns are worked with the resuU of giving a fair average 

 aitenuation and yield viewed from the Jamaica standpoint, but 

 then they are worked more on the lines of a " mother" cistern, 

 i.e. are prevented from going radically sour by being always kept alive 

 by periodical doses of molasses and dunder ; but in these cases I have 

 not seen real high priced i um produced. But when we understand that 

 a great deal of the unsatisfactory nature of the fermentation may be re- 

 ferred back to the weakened yeast, we are inclined to enquire whether 

 this cannot be remedied. Supposing that we cannot when working with 

 the trash cistern have a fermentation which would compare in rapidity 

 of attenuation and dercentage yield of alcohol with an ideally pure al- 

 cohol fermentation, what amount of slowness is necessary for the pro- 

 duction of good rum ? Is it absolutely necessary that the fermentation 

 should last 2 or 3 weeks, or could it not be reduced, let us say, not to be 

 too ambitious, down to 7-10 dajs without injuring the quality of the 

 rum ? And supposing that the yield must suffer what is the limit of 

 the amount of quantity to be sacrificed to quality? In other words, 



