BY-PRODUCTS OF SUGAR MANUFACTURE. 35 



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 will be formed 

 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 theo- 

 retical 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 percentage 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 always, however, more or less water vapor escaping 

 with the alcohol and consequently it is impossible to secure 

 absolute alcohol without after-treatment, although in the modern 

 still a very high grade is often recovered 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 accomplish this, it was said to be "under proof," and when 

 the gunpowder was lighted easily by it, it was said to be "over 

 proof." 



By an act of the English Parliament, the term "proof spirit" 

 was fixed as one which contains exactly ^i.j of an equal volume 

 of water (distilled) at 51 F., which represents 57.1 per cent 

 of alcohol by volume, or 49.3 per cent 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. 



