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 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 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 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 12/13 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.

Table for calculating the percentage of alcohol.[3]

Volume.Specific gravity at—Volume.Specific gravity at—Volume.Specific gravity at—Volume.Specific gravity at—
15.56°25°15.56°25°15.56°25°15.56°25°
15.5615.5615.5615.5615.5615.5615.5615.56
P. ct.P. ct.P. ct.P. ct.
10.99850.9970260.96980.9655510.93230.9246760.87450.8665
2.9970.995327.9691.964652.9303.922577.8721.8641
3.9956.993828.9678.963153.9283.920578.8696.8616
4.9942.992229.9665.961754.9262.918479.8664.8583
5.9930.990930.9652.960355.9242.916480.8639.8558
6.9914.989331.9643.959456.9221.914381.8611.8530
7.9898.987632.9631.958257.9200.912282.8581.8500
8.9890.986833.9618.956758.9178.910083.8557.8476
9.9878.985534.9609.955659.9160.908184.8526.8444
10.9869.984635.9593.953860.9135.905685.8496.8414
11.9855.983136.9578.952161.9113.903486.8466.8384
12.9841.981537.9565.950762.9090.901187.8434.8352
13.9828.980138.9550.948963.9069.898988.8408.8326
14.9821.979339.9535.947364.9047.896989.8373.8291
15.9815.978740.9519.945665.9025.894790.8340.8258
16.9802.977341.9503.943866.9001.892391.8305.8223
17.9789.975942.9490.942467.8973.889592.8272.8191
18.9778.974643.9470.940268.8949.887093.8237.8156
19.9766.973344.9452.938269.8925.884694.8199.8118
20.9760.972645.9434.936370.8900.882195.8164.8083
21.9753.971946.9416.934371.8875.879696.8125.8044
22.9741.970647.9396.932372.8850.877197.8084.8003
23.9728.969248.9381.930773.8825.874698.8041.7960
24.9716.967849.9362.928874.8799.871999.7995.7914
25.9709.966850.9343.926775.8769.8689100.7964.7865

Molasses as a fuel.—Many experiments have been made, using this substance as a sugar-house fuel, and while ordinarily it may be better employed in some other manner, at the same time where no other provision is made for the use of this material, and where there is a scarcity of fuel as well, satisfactory results may be secured in its combustion if it is properly handled.