For thick washes, which tends to obstruct the slits of the cap, Barbet has devised the cap shown at the right in Fig. [25]. This cap extends down to the plate itself, and has very narrow slits in its periphery. With such a cap as shown in Fig. [24], the bran, sediments, etc., would tend to settle upon the top of the cap, enter beneath it and through the slits. The cone-shape of the top of this cap prevents the deposit of dregs thereon and the very narrow slits oppose the entrance of bran or sediment.
While, for the sake of clearness, an old form of concentrator, G, has been shown, the concentrator, preheater for the wash, and condensers, to-day, are usually composed of bundles of tubes through which the vapors pass surrounded by water or the cool wash. These should be of bronze or copper and made without solder. The tubes should be capable of being taken out for cleaning or repairing.
In many distilling apparatuses the distilling column and the rectifying column are in two parts, one beside the other. This overcomes the objection of having a very high column and also prevents the low wines, i.e., the weak alcoholic liquor after its first concentration, from passing into the wash as it would do with the continuous column.
Fig. 26.—Steam Regulator.
In order that the amount of steam entering the column may be regulated, the column is usually provided with a steam regulator (Fig. [26]); whose principle of operation may be easily under stood by referring to Fig. [22]. It comprises an upper and a lower chamber Z Z′ connected by a central tube K which projects down nearly to the bottom of the lower chamber. A pipe W communicates with the steam chamber R of the column and enters the chamber Z above the level of the water contained therein. In the upper chamber Z′, is a float X, connected to the differential lever T of a steam valve T′ which controls the inlet of steam passing through pipe S to the steam chest R. The principle of operation is very simple. When the pressure in the steam chest R becomes too great, steam in the pipe W and chamber Z forces the water therein up in tube K, thus lifting the float X and closing the steam entrance valve T′. When the pressure of steam is low, the level of the liquid in Z rises and liquid in Z′ runs into Z, the float X falls opening valve T′ and allowing a greater flow of steam.
Fig. 27.—Gauge Glass for Regulatur.