CANE SUGAR. 



compared with the amount actually recovered ; the balance is to be found in 

 the feints in the lees and in leaks from the still; the alcohol in these residues 

 should also be determined and all expressed as percentages of that originally 

 present ; finally an account of the alcohol produced per unit of total and of 

 fermentable sugar should be made out. 



Amount of Alcohol obtainable from Molasses. Fermen- 

 tation proceeds roughly under the equation 



C 6 H 12 6 = 2C 2 H 5 OH -f 2C0 2 

 Glucose Alcohol Carbon dioxide. 



Following on this equation 1 Ib. of glucose or *95 Ib. of cane sugar could 

 afford -51 lib. of alcohol and -489 Ib. carbon dioxide; this yield is never 

 obtained in practice even when the distillation losses are disregarded. Peck 

 and Deerr 5 fermented in pure culture a number of molasses with tropical yeasts 

 and found that on an average 90 per cent, of the fermentable sugars were 

 recovered in alcohol, the amount as indicated from the above equation being 

 put equal to 100. In addition, in Hawaiian molasses they found from 4 '05 

 per cent, to 7 '32 per cent, of the sugars were unfermentable ; previously 

 in Egyptian molasses Pellet had observed 2 '40 per cent, of 'glutose* 

 and Deerr had found up to 3 per cent, in Demerara molasses. The total 

 amount of sugars in cane molasses varies from 45 per cent, to 65 per cent, so 

 that it is impossible in the absence of an analysis to state what quantity of 

 alcohol can be obtained from a molasses. 



Analyses. The analyses necessary to a distillery control are indicated 

 briefly below. 



Density of Wash. The methods given for juices in Chapter XXIV. are 

 applicable. 



Attenuation. The attenuation is the difference between the initial and 

 final density, water being put equal to 1000 ; thus wash initially at 1063 and 

 finally at 1015 is said to have attenuated 48 degrees. For each degree of 

 attenuation it is customary to assume the presence of so much proof spirit ; 

 a common allowance is 1 per cent, of proof spirit for every 5 degrees of attenua- 

 tion. As the result of a series of laboratory fermentations with pure cultures, 

 the writer found 1*17 per cent, of proof spirit for every 5 degrees of attenua- 

 tion. This method is not meant as an accurate determination of percentage of 

 proof spirit, but as a guide to revenue and customs authorities. 



Sugars. There is no necessity to determine the cane sugars as such ; the 

 sugars should be determined after inversion following the methods given in 

 Chapter XXIII. ; as the sugars will be mainly dextrose and levulose in approxi- 

 mately equal proportions, it will be best to calculate them as invert sugar. 



540 



