As it is often desirable to change the pressure of steam in the column at various points in the operation, the best regulators are usually provided with means to that end.
In order to measure the output of the still, there is attached thereto a gauge glass (J in Fig. [22]), a diagram of which is shown in Fig. [27]. This consists of a jar A connected at its lower end at b by an annular passage B to a chamber E from which proceed the taps F. Centrally through the passage B passes a tube c connected at its lower end to the pipe C leading from the condenser. The tube C c projects upward into the jar A and is open at its upper end.
Fig. 28.—Continuous Distilling Apparatus, with External Tubular Condenser.
Now the opening b is of a certain size and it is obvious that it will carry off a certain amount of liquid when running full or the amount allowed to flow out by the exit tap F. If now, more than that quantity of alcohol is produced, the alcohol will rise in the jar A until the rate of inflow and outflow is equal. If, however, the still is producing less than that quantity then the level of liquid in A will gradually drop. Hence, by observing the level of the liquid in A and its constancy or variation in level, it is possible to tell precisely how much alcohol is running per hour and if the rate is steady. The jar A is provided with a cap G whereby an alcoholometer may be inserted into tube c for the purpose of testing the strength of the liquor. The taps F are for the purpose of collecting the first runnings, the pure alcohol and the last runnings or “feints.”
Fig. 29.—Detail of Chamber, Continuous Still.
These principles are also embodied in the apparatus designed by the Vulcan Copper Works Co., of Cincinnati, and illustrated in Fig. [28]. The apparatus comprises the still, a wash heater and a condenser. The still is composed of a series of chambers from 12 to 24, the internal construction of which is shown in Fig. [29]. Each chamber consists of a peculiarly perforated plate A, a drop pipe B, a seal C, into which the drop pipe from the plate above projects, and a central standard D.