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yeast did not : therefore the aroma must have been produced from No. 18 

 yeast acting on some substances in the dunder. But dunder is simply the 

 residue of wash which has been previously fermented and distilled, and is 

 in fact the residue of cane juice, and skimmings and molasses. But neither 

 cane juice, which contains those substances which eventually go to form 

 skimmings, nor molasses, gave the aroma, Perhaps then it was due 

 to the process of boiling in the still ? Accordingly pure cane juice 

 and molasses were allowed to undergo fermentation and were then 

 distilled, and fresh wash set up with the resulting dunder, but no 

 aroma was developed : it was evident then that dunder, as dunder, 

 had nothing to do with the formation of the aroma in question. I 

 must here make a short digression. While I was engaged in Europe 

 in isolating different yeasts from the materi Is (molasses and dunder) 

 sent to me from Jamaica, I searched for a long time in vain for a yeast 

 capable of producing a definite aroma. With this object I must 

 have made certainly not less than two hundred pure cultivations. One 

 yeast only attracted my attention as seeming to be able to produce a 

 faint aroma, certainly more than the rest. This yeast therefore I 

 examined more closely. On testing the mixture of dunder and mo- 

 lasses which I was fermenting with this yeast, it was found to be 

 exceedingly acid. It was thought therefore that such a great acidity 

 was injurious and might probably interfere with and prevent the yeast 

 from exercising its physiological functions to the full. I accordingly 

 partly neutralised the acidity of the dunder with a few drops of caustic 

 soda, and put the liquid which No. 18 yeast had nearly finished fermenting, 

 away to stand. After standing for about three days and when fermen- 

 tation was at an end the characteristic aroma was developed. This yeast 

 I afterwards named No. 18 and is the one used in these experiments. 

 I had not time then to proceed any further with the question, and 

 remained satisfied with the explanation I have adduced. When 

 however my experiments in Jamaica led me to see that the aroma could 

 not be produced from fresh cane juice or molasses, or even from cane 

 juice and untreated skimmings, or from molasses and untreated skim- 

 mings, but yet could be produced by the help of the dunder acted upon 

 by No. 18 yeast and bearing in mind my former experiment in Europe, 

 of partially neutralizing the dunder, which had resulted in the produc- 

 tion of the aroma, I bethought me of the treatment which the cane juice 

 undergoes in the boiling house. 



This as a general rule in Jamaica consists in treating the cane juice 

 with caustic lime. I determined therefore to try the experiment of 

 fermenting cane juice which had undergone this treatment. But as an 

 alkaline medium is unfavourable to alcoholic fermentation, and as the 

 alkaline skimmings from the boiling house are brought down, whenever 

 possible, on acid dunder, I determined in order to test the efficacy of the 

 treatment and at the same time to provide a favourable fermenting 

 medium for the yeast, to neutralise the alkalinity of the treated cane 

 juice with sulphuric acid, using a sufficient excess to produce a slight 

 acidity : dunder of course could not be used in this experiment. A por- 

 tion of fresh cane juice was therefore taken and divided into three parts 

 I, II and III. No. I was made alkaline with caustic lime, No. II was 

 not treated and served merely as control experiment, while No. Ill was 

 not treated with temper lime, but was faintly acidulated with sulphuric 



