(e) Weaker alcohols which are usually re distilled with the raw spirit.
(f) The so-called last runnings or feints, which usually contain some amylic alcohol, are used in various industries, as for example, in the textile industries, on account of their solvent power over fats and oils; in the manufacture of ethereal oil and also in the chemical labora By means of filtration and •fractional dis tillation, about 85 to 90 per cent of the raw spirit is obtained as rectified spirit, therefore it has been the object of many experiments to improve this yield.
The only successful defuselizing process is that of Traube, by which a sufficiently con centrated potash solution is mixed with the spirit in accordance with its strength and heated to 60° to 70° C. to F.). Two layers are formed, the upper, which is dark-colored and foul-smelling, contains the impurities, and in the lower we find the purified alcohol with the salt solution. After removing the former, the latter is distilled in a rectificator and con centrated; 97 to 98 per cent of the raw spirit is secured by this process.
But after all, filtration through charcoal is the best practical refining process for brandies, while filtration and fractional distillation are best employed for Cologne spirits. In large distilleries the manufacture of Cologne spirit and rectified alcohol directly from the mash is both practically and technically the most advantageous when manufactured in apparatus based on Ilges' system. In ordinary distillation and refining, a deterioration of the material takes place, as the fermentation products of the normal mash are purer than those of the raw spirit. The presence of atmospheric air in the condenser induces the formation of aldehydes and, in the raw spirit, foul-smelling substances. By means of slow evaporization in the rectifier fusel oil is decomposed, while in the new auto matic spirit apparatus, it is obtained as fusel oil. But this apparatus is equipped with very effective dephlegmators and rectificators, so that it is an easy matter to precipitate the fusel from the alcoholic vapors and to receive only the purest alcoholic vapor in the condenser. In order to prevent an accumulation of fusel in the ever-returning phlegma, temperature regula tors and fusel separators are attached in the latter, so that the phlegma constantly has a uniform temperature and fusel can never be in excess. The advantages of this process are not only the dispensing with rectification and filtra tion, but also the production of a pure valuable spirit of about 95 per cent alcohol by volume (190 proof), while the valuable and untaxed fusel is obtained as a by-product. In addition,
the 1,'field is greater, as the loss caused by recti fication is avoided.
Absolute anhydrous pure alcohol cannot be made in this way, nor can it be prepared by repeated distillation, as alcohol is in itself hygro scopic and tenaciously holds on to the last traces (3 to 4 per cent) of water. This last remnant of water can only be removed by very effective dehydrating agents; as for example, freshly burned lime, anhydrous carbonate of potash, anhydrous white copper. sulphate, fused calcium chloride and especially metallic sodium. By distillation over any of these substances the water is absorbed and an absolutely anhydrous pure alcohol is produced. This process is, how ever, only carried out in chemical laboratories and as a precautionary measure this alcohol is stored in small bottles with any of the above substances. This precaution is taken in order to prevent the absorption of moisture by the alcohol. The distillation of alcohol in the United States in the year ended 30 June 1915 was 81,101,064 gallons, of which 42,742,161 gal lons were Cologne spirits and 33,854 gallons thigh The distillation of alcohol, as in many other distillatory operations, is merely a mechanical process of purification, as no chemical change takes place, because the distillates have the same chemical composition as the original substance. Distillation is only a mechanical separation of the secondary ingredients from the principal one. Some substances, as for instance, glycer ine, when distilled in presence of atmospheric air, will decompose. In such cases the distilla tion is done in a partial vacuum. By means of an air-pump the pressure of the air is reduced until the boiling point is lowered to that degree at which the distillation can take place without decomposition. It is well known that matter will boil at a lower temperature, when the pressure is decreased; and that decomposition is less liable to occur. Again, other substances cannot be distilled in the presence of much oxygen, so that carbonic acid, hydrogen, or other gases are forced into the stilt. These gases pass over with the vapors of distillation. This process is called the distillation in an atmosphere of an indifferent gas.