T H E C U B A R E V I E U' 15 



Invert sugar 

 enzvme — > 



(Ce H12 Oe (dextrose) Ce H12 Oe (leviJose) 



180 M. W. 180 M. W. < 



— > C2 H5 -OH (ethyl alcohol) +4CO2 (carbon dioxide) 

 184 (2 M. \V.) 176 CM. W. 



The theoretical yield then of alcohol from sucrose would be o3% and from invert sugar 

 51%. In practice, however, this j'ield would not be experienced on account of the yeast 

 converting some of the sugars into substances other than alcohol and carbon dioxide. These will 

 consist mostly of gh'cerine and succinic acid and will amount to 4 or 5% . 



Since the working conditions determine to a very great extent the yield of alcohol, it is 

 obvious that a thoroughly efficient person should be in charge of this work. In the selecting 

 of cultures for the fermenting, the manufacturer should use only the purest, otherwise acetic 

 acid and other foreign substances wiU be found during fermentation, thus decreasing the yield 

 of the alcohol as well as lowering its purity. 



Where the percentage of sucrose and glucose of a molasses is known, it is a simple matter 

 to calculate the theoretical amount of alcohol to be recovered and by knowing the efficiency 

 of the factory, a factor may be obtained which multiplied by the theoretical yield will give the 

 true amount of alcohol to be expected. In this manner it is easy to determine the price that 

 may be paid for any molasses. 



The separation of the alcohol from the water and dirt (lees) is accomplished in an apparatus 

 termed a "'still." In this the liquor is heated by steam which causes the alcohol to evaporate. 

 Since ethyl alcohol boils at a temperature of 78° or a little higher, depending upon the percent- 

 age present, it may be separated from the water and impurities during the evaporation, and 

 recovered from the coils of the condenser in a fairly pure state. 



There is alwaj'^s, however, more or less water vapor escaping with the alcohol, and conse- 

 quently it is impossible to secure absolute alcohol without after-treatment, although in the 

 modern still a very high grade is otten recoverd in the first distillation. 



In this connection the strength of alcohol is usually determined by referring it to 

 "proof," which is an old English system used before modern methods of testing spirits were 

 available. In its original application, gunpowder was moistened with the spirit and the 

 mixture subjected to the flame of a match. When just enough alcohol was present to set fire 

 to the powder, it was said to be "proof spirit." If not enough alcohol was present to accom- 

 plish this, it was said to be "under proof," and when the gunpowder was lighted easily bj^ it, it 

 was said to be "over proof." 



By an act of the English Parliament, the term "proof spirit" was fixed as one which con- 

 tains exactly 12-13 of an equal volume of water (distilled), at 51° F., which represents 57.1% of 

 alcohol by volume, or 49.3% by weight. 



The simplest method of determining the percentage of alcohol is by the use of a gravity 

 spindle for liquids lighter than water, and by referring to the accompanying table for this 

 purpose, the percentage of alcohol may be ascertained. 



Table for calculating the percentage of alcohol. 



Specific gravity Specific gravity Specific gravity Specific gravity 



at — at — at — at — 



Vol- Vol — — Vol- Vol 



ume ume ume ume 



15.56 25 15.56 25 15.56 25 15.58° 25° 



15.56 15.56 15.56 15.56 15.56 15.56 15.56 15.56 



P.ct. P.ct. P.ct. P.ci. 



1 0.9985. 0.9970 26 0.9698 0.9855 51 0.9323 0.9246 76 0.8745 0.8665 



2 .9970 .9953 27 .9691 .9346 52 .9303 .9226 77 .8721 .8641 



3 .9956 .9938 28 .9678 .9631 53 .9283 .9205 78 .8696 .8616 



4 .9942 .9922 29 .9665 .9617 54 .9262 .9184 79 .8664 .8583 



