Book of American Baking / A Practical Guide Covering Various Branches of the Baking Industry, Including Cakes, Buns, and Pastry, Bread Making, Pie Baking, Etc.

by Various

Distillation Test.—After the fermentation in the generating flask has ceased, and no more bubbles rise to the surface of the fluid, test it by distillation. For this purpose we first filter the saccharine fluid to remove the yeast cells. Place the clear filtrate in a clean flask, stop it with a perforated rubber cork, and connect it by means of a bent glass tube with a cooling apparatus. Figure 6 shows such an apparatus. The vapor generated from the filtrate contained in the flask passes through the coil in the cooler, as shown in the illustration. The cooler is provided with tube connections at the lower and upper ends, which can be fitted with perforated corks, through which glass tubes may be inserted.

Fig. 6.

The lower tube by means of rubber tubes is connected with the cold water faucet, not shown in the illustration; the flow of cold water around the coil can be regulated at the faucet and drawn off at the upper tube.

In lieu of a cooler as shown, one can be constructed by leading the tube of the filtrate flask into a somewhat wider and longer glass tube, which is connected with a second bottle. The long glass tube, in this case, must be kept cool by constantly pouring cold water over it during distillation.

When all connections have been made tight, heat the filtrate over an alcohol lamp to a boiling point, the flask having been placed on a piece of wire gauze to equalize the heat. The arising vapors passing through the coil are condensed, and drip like tears into a receptacle placed underneath the cooler. This evaporating and condensing of a fluid is called distillation.

The portion of the condensed fluid coming over at the beginning will be found, if tasted, to be very strong spirits of alcohol. Light it with a taper, it will produce a large bluish flame.

As the distillation continues the spirits coming over lose gradually in strength until finally very little else but the vapors of water are condensed. Water boils at 212 degrees F., spirits of alcohol at 172 degrees F. We would therefore infer that at the beginning of distillation it is possible to recover alcohol only if the infusion was heated to 176 degrees F.

This view, however, is erroneous. The boiling point of the mixture is only slightly greater than that of pure alcohol, and the generated vapors are already at the beginning and combination of both fluids, although at first the proportion of alcohol is the greater.