Fig. 38 represents a simple rectifying apparatus designed for small or medium sized plants, and manufactured by the Vulcan Copper Works Co., of Cincinnati. The still is upright, with a chambered column above it, of the usual type. The chambers are fitted with a vapor boiling pipe and cap and a drop pipe, and each is provided with cocks whereby it may be drained for cleansing. Above the column is a separator, comprising a casing containing a series of tubes. The vapor from the column circulates around the tubes through which passes a current of cool water. The condenser is of the same construction as the separator and is provided with a gage glass and a draw-off cock. The operation is the same as in other simple rectifiers; part of the vapor from the column is condensed in the separator and passes back on to the upper plates, while the more highly vaporized portions pass over into the condenser. [Illustration: FIG. 38.--Rectifying Apparatus with External Tubular Condenser. (_To face page 94_)] The diameter of the still is large relatively to its depth so as to yield an economical and at the same time highly effective distribution of heat through the charge. This also affords an extended boiling area from which the vapor rises evenly and regularly, thus ensuring conditions peculiarly conducive to produce the best fractionating. The floor space required for this still and others of the same character built by this company is very compact and excessive weight on the top floor of the building is dispensed with. We have shown in Figs. 39 and 40 two forms of rectifying apparatus, one a twin column Barbet rectifier and the other a rectifier of the Gillaume type combined with inclined column still. [Illustration: FIG. 39.--Twin Column Barbet Rectifier.] In the twin column apparatus, Fig. 39, the first column or clarifier _A_ receives the raw phlegm and accomplishes the elimination of ethers. The clarified phlegm passes then to the second column where the alcohol is separated from the last runnings or fusel oil. In other words, the phlegm or impure raw alcohol is only raised to such a temperature in the first column as to drive off the very volatile constituents such as the ethers. These therefore pass off at the top of the first column into the condenser _C_, the retrogradation or condensed alcohol being returned to _A_, while the boiling phlegm taken from the middle of the column and still containing the aldehydes, oils, etc., is conducted by a pipe _E_ to the second column _B_ wherein the last runnings or amylic oils, etc., are separated from the purified spirits. The vapors in this column are carried to the condensers _D_ and _F_ and from there to a refrigerator _G_. The fusel oils are extracted from the plates slightly below the center of the column and are carried to an oil concentrating apparatus _H_.