In Fig. 34 is shown a form of Gillaume still designed to distill all sorts of liquids whether thin or thick. The wash is supplied from an overhead tank to a regulating tank _K_ from which a pipe _k_ leads to a regulating tap _m_. The wash re-ascends into the wash heater _B_ and when heated descends by pipe _F_ into the uppermost compartments of the column _A_. The vapor passes to the condenser _B_, by a pipe _H_, and the spent wash is discharged by a siphon _C_. In addition to the parts above referred to, _a_ designates entrance of wash into heater, _b_ exhaust test tube, _d_ steam entrance tap _G_ alcohol test glass, _G¥_ exhaust test glass, _o_ valve for regulating strength of spirit, _O_ steam regulator, _p_ water entrance tap, _r_ exit tap, and _D_ the spent wash extractor. The Gillaume apparatus is particularly valuable for the production of industrial or agricultural alcohol. It is claimed that it is easily understood and operated even by unskilled labor, while it produces a large proportion of alcohol of a high strength. A view of a complete apparatus on a large scale is shown in the Fig. 40 in the chapter on rectification. CHAPTER V. RECTIFICATION. The product of the distillation of alcoholic liquors, which is termed _low wine_, does not usually contain alcohol in sufficient quantity to admit of its being employed for direct consumption. Besides this it always contains substances which have the property of distilling over with the spirit, although their boiling points, when in the pure state, are much higher than that of alcohol. These are all classed under the generic title of _fusel-oil_; owing to their very disagreeable taste and smell, their presence in spirit is extremely objectionable. In order to remove them, the rough products of distillation are submitted to a further process of concentration and purification. Besides fusel-oil, they contain other substances, such as aldehyde, various ethers, etc., the boiling points of which are lower than that of alcohol; these must also be removed, as they impart to the spirit a fiery taste. The whole process is termed _rectification_, and is carried on in a distillatory apparatus. As before stated, the wash as discharged into the still consists of alcohol mixed with water and a variety of impurities from which the alcohol must be separated. In order that the process may be better understood we will assume that a mixture of pure alcohol and water is to be operated on in place of the wash as above referred to. Distillation in this case is intended to deprive the water of its alcohol, the operation theoretically leaving water in one chamber and alcohol in another. This is accomplished by reason of the differences in the boiling points of water and alcohol. The alcohol vaporizes at a lower degree (173∞ F.) than water (212∞ F.) Thus the liquid at the end of the operation has been divided into two parts or _fractions_.