ALCOHOL.— Kectification.

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Methyl alcohol has already been considered. (SeeAcetic Acid .)

Ethyl alcohol is the most important of all thesecompounds. It was known to the alchemists. Itsdiscovery is said to be due to Alisucasis andArnold de Vili.eneitve, in the twelfth century.Raymond Lully , about the fourteenth century, wasacquainted with spirits of wine, which ho calledaqua ardens, and made by distilling wine and con-centrating the distillate by means of potassiumcarbonate. Liewitz and Richter subsequentlysucceeded in completely separating the water bymeans of quicklime. Alcohol was first analyzedby Du Saussure, who separated it into 100 parts byweight of olefiant gas and 68'58 of water: about equalvolumes of olefiant gas (ethane, C.,II 4 ) and aqueousvapour (II 2 0). The vapour density of alcohol, asgiven by Gay Lussac , agrees with this composition.

In a general and practical sense, by alcohol is un-understood the pure spirit obtained by the dis-tillation of liquids which have undergone v.'nousfermentation. It is the intoxicating principle of allvinous and spirituous liquors, as wine, brandy, whiskey,&c. Distilled from wine, it bears the name spiritof wine.

After the completion of fermentation distillationof the fermented body affords it cither in a more orless concentrated state. Mere distillation, however,will not yield absolute alcohol, that is, alcohol freefrom water. For though absolute alcohol boils at173°Fahr. (78°'4 C.), it has a great affinity for water,and dilution by water contracts its volume and raisesits boiling point, so that the aqueous vapour cor-responding to this temperature passes over with thespirit. At the lowest temperature at which thedistillate is drawn off some aqueous vapours risewith the alcohol, and both are condensed simul-taneously in the receiver; therefore, whatever theheat may be, the resulting alcohol is not anhydrous,but exhibits a density of 0‘820 to 0'830.

To procure absolute alcohol is a difficult and tedi-ous operation: spirit of wine has to be distilled at amoderate heat from some liygrometric substance,such as anhydrous copper sulphate, calcium chloride,potassium carbonate, or quicklime. The best adaptedfor the purpose is quicklime reduced to coarsepowder and put into a retort with the alcohol, andthe whole mixed by agitation; the neek of the retortis then securely corked, and the mixture left forseveral days, during which period the water uniteswith the quicklime and converts it into calciumhydrate (CaII 2 0 2 ), leaving the anhydrous spirit,which may be distilled off from the mixture by theheat of a water-bath.

Fig. 1 is the apparatus usually employed in thelaboratory for this purpose : A is a glass retort; heatis applied by the lamp, c ; d is a Liebig ’s condenser,through which the tube receiving the beak of theretort passes to the flask, f. Cold water from thetank, e, enters the condenser, n, by the funnel tube,f and the heated water is discharged by h into thevessel, c. The mouth of the receiver is closed by aperforated cork, to prevent the access of air and the

absorption of aqueous vapours. The dilute alcoholand coarsely - powdered dehydrating substance areintroduced through the stoppered opening, d, thestopper replaced, and the- distillation carried on atas low a temperature as possible— 173° to 17 6°Fahr. (78° to 80° C.). Repeated distillations withfresh portions of the hygroscopic substance used arenecessary to free the alcohol completely from water.

To enable the quicklime to abstract all the waterit should be left in contact with the alcohol for atleast three or four days at the temperature of 95°Fahr. (85° C.): 1 part of 91 per cent, alcohol requiressomewhat more than 1 part of quicklime in order toyield alcohol of 99-2 per cent, by filtration, andabsolute alcohol by slow distillation. Alcohol of94 per cent, requires only § part of lime, and alcoholof 97 per cent, only ^6 of a part.

Mexdelejeff states that to obtain the alcoholabsolute, spirit of not more than - 792 specific gravitymust be taken, and its digestion over the quicklimecontinued for not less than two days, or else for afew hours at between 122° to 140° Fahr. (50° to00° C.). Even then, on distilling, he found only themiddle portions anhydrons.

Fig 1.

a 6 *.

By boiling the spirit with the lime in a vesselfitted with an inverted condenser for about an hour,and then distilling, the whole product is obtainedanhydrous. If the spirit contains more than 5 percent, of water it is necessary to repeat the treatmentwith lime two or more times. But with weak spiritcare must be taken at first not to fill more than halfthe space occupied by the spirit with lime, as other-wise the vessel may be broken by the slaking of thelime. In this way several litres of spirit may beconverted into absolute alcohol in a few hours.

A singular mode of concentrating alcohol hasbeen proposed by Soemmering, lie used an ox ora calf bladder, which was soaked for some time inwater, and freed from the fat and the attachedvessels. After being again inflated and dried, itwas coated, the outside twice and the inside fourtimes, with a solution of isinglass, and then chargedwith diluted spirit, leaving a small space vacant.On exposing it to heat the water evaporates, whilethe alcohol remains. The bladders can be repeat-edly used. It is stated that by this means, withproper attention to the degree of heat applied,