FERMENTATION WITH SPECIAL REFERENCE TO THE SUGAR HOUSE. 



Alcohol in Wash and Lees. Take a definite quantity of material, 

 neutralize with caustic soda, and distil until about 90 per cent, of the original 

 volume has been collected ; make up with water to original volume and 

 determine the density of the distillate by means of a pycnometer, whence the 

 percentage of alcohol is obtained by reference to the table given below. As 

 lees usually contains very little alcohol it will be well to take a large quantity, 

 say 1000 c.c., distil over 500 c.c., redistil the distillate until 250 c.c. have 

 come over, and finally determine the density of this portion; otherwise the 

 density of the distillate differs so little from unity that a large percentage 

 error may arise. 



Alternatively the fractionating still heads of large cooling area, listed by 

 dealers in apparatus, may be used to obtain the alcohol concentrated in a 

 distillate of small volume. 



A form of pycnometer which is of great use in the tropics is that due to 

 Boot, where the bottle containing the liquid is enclosed in a second, the space 

 between them being evacuated; liquids may be cooled down to 15 C. and 

 kept in the inner bottle without change of temperature and without the con- 

 densation of water on the outside of the bottle. 



The table connecting density and percentage of alcohol given below is 

 referred to water at 60 F. ; in the tropics materials must be cooled down to 

 near this temperature ; in the absence of ice this is best done by dissolving in 

 water a salt such as thiosulphate of soda. Small variations from the standard 

 temperature may be corrected by the use of the expression : 



where D is the required density, D' the observed density, d the difference in 

 temperature in centigrade degrees between 15'5 C. (60 F.) and that at which 

 the observation was made. 



A table connecting degree Sikes and specific gravity at 84 F. for strong 

 spirits is added as being useful in certain districts. 



REFERENCES IN CHAPTER XXV. r . 



1 . Die Hefepilze. 



2. Perrault. Le Rhum. 



3. Bull. Sot. Dept. Jamaica., May, Aug., Sept., 1895; Jan., 1896. 



4. Wochenschrift fur Brauerei, 1887, No. 44. 



5. Bull. 28 Agric. H.S.P.A. 



6. Arch. 1894, 529. 



541 



