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Encyclopedia Britannica - Main :: AJA-ALL |
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ALCOHOL , in commerce, the name generally given to " spirits of wine "; in systematic organic chemistry it has a wider meaning, being the generic name of a class of compounds (hydroxy hydrocarbons) of which ordinary alcohol (specifically ethyl alcohol) is a typical member (see ALCOHOLS). The word " alcohol " is of Arabic origin, being derived from the particle al and the word kohl, an impalpable powder used in the East for painting the eyebrows. For many centuries the word was used to designate any fine powder; its present-day application to the product of the distillation of wine is of comparatively recent
Paracelsus
Paracelsus
Ordinary alcohol, which we shall frequently refer to by its specific name, ethyl alcohol, seldom occurs in the vegetable kingdom; the unripe seeds of Heracleum giganteum Ethyt and H. Sphondylium contain it mixed with ethyl alcot,ol. butyrate. In the animal kingdom it occurs in the urine of diabetic patients and of persons addicted to alcohol. Its important source lies in its formation by the " spirituous " or alcoholic fermentation " of saccharine juices. The mechanism of alcoholic fermentation is discussed in the article FERMENTATION, and the manufacture of alcohol from fermented liquors in the article SPIRITS. The qualitative composition of ethyl alcohol was ascertained by A. L. Lavoisier, and the quantitative by N. T. de Saussure in 18o8. Sir Edward Frankland showed how it could be derived from, and converted into, ethane; and thus determined it to be ethane in which one hydrogen atom was replaced by a hydroxyl group. Its constitutional formula
Pure ethyl alcohol is a colourless, mobile liquid of an agreeable odour. It boils at 78.3 C. (760 mm.); at -9o C. it is a thick liquid, and at -13o it solidifies to a white mass. Its high coefficient of thermal expansion, coupled with its low freezing point, renders it a valuable thermometric fluid, especially when the temperatures to be measured are below -390 C., for which the mercury thermometer cannot be used. It readily inflames, burning with a blue smokeless flame, and producing water and carbon dioxide, with the evolution of great heat; hence it receives considerable application as a fuel. It mixes with water in all proportions, the mixing being attended by a con-traction in volume and a rise in temperature; the maximum contraction corresponds to a mixture of 3 molecules of alcohol and r of water. Commercial alcohol or " spirits of wine " contains about :90 % of pure ethyl alcohol, the remainder being water. This water cannot be entirely removed by fractional distillation, and to prepare anhydrous or " absolute " alcohol the commercial product must be allowed to stand over some dehydrating agent, such as caustic lime, baryta, anhydrous copper sulphate, &c., and then distilled. Calcium. chloride must not be used, since it forms a crystalline compound with alcohol. The quantity of alcohol present in an aqueous solution is determined by a comparison of its specific gravity with standard tables, or directly by the use of an alcoholometer, which is a hydrometer graduated so as to read per cents by weight (degrees according to Richter) or volume per cents (degrees according to Tralles). Other methods consist in deter-mining the vapour tension by means of the vaporimeter of Geissler, or the boiling point by the ebullioscope. In the United Kingdom " proof spirit " is defined' as having a specific gravity at 51 of 12/13 (.92308) compared with water at the same temperature. The " quantity at proof " is given by the formula
Etymology. quantity of sample X (degrees over or under proof + xoo) divided by roo. The presence of water in alcohol may be detected in several ways.. Aqueous alcohol becomes turbid when mixed with benzene, carbon disulphide or paraffin oil; when added to a solution of barium oxide in absolute alcohol, a white precipitate of barium hydroxide is formed. A more delicate method consists in adding a very little anthraquinone and sodium amalgam; absolute alcohol gives a green coloration, but in the presence of minute traces of water a red coloration appears. Traces of ethyl alcohol in solutions are detected and estimated by oxidation to acetaldehyde, or by conversion into iodoform by warming with iodine and potassium hydroxide. An alternative method consists in converting it into ethyl benzoate by shaking with benzoyl chloride and caustic soda. Alcohol is extensively employed as a solvent; in fact, this constitutes one of its most important industrial applications. It dissolves most organic compounds, resins, hydrocarbons, fatty acids and many metallic salts, sometimes forming, in the latter case, crystalline compounds in which the ethyl alcohol plays a role similar to that of water of crystallization. This fact was first noticed by T. Graham, and, although it was at first contradicted, its truth was subsequently confirmed. In general, gases dissolve in it more readily than in water; roo volumes of alcohol dissolve 7 volumes of hydrogen, 25 volumes of oxygen and 16 volumes of nitrogen. Potassium and sodium readily dissolve in ethyl alcohol with the production of alcoholates of the formula C2 H5 OK(Na). Reactions. These are voluminous white powders. Sulphuric acid converts it into ethyl sulphuric acid (see ETHER), and sulphur trioxide gives carbyl sulphate. The phosphorous haloids give the corresponding ethyl haloid. Ethyl chloride (from the phosphorus chlorides and alcohol) is an ethereal liquid boiling at 12.5 C., soluble in alcohol, but sparingly so in water. Oxidation of ethyl alcohol gives acetaldehyde and acetic acid. Chlorine oxidizes it to acetaldehyde, and under certain conditions chloral (q.v.) is formed. In almost all countries heavy taxes are levied on manufactured alcohol mainly as a source of revenue. In the United Kingdom Industrial the excise duty is eleven shillings per proof gallon of akonoi. alcohol, while the customs duty is eleven shillings and fivepence; the magnitude of these imposts may be more readily understood when one remembers that the proof gallon costs only about sevenpence to manufacture. The great importance of alcohol in the arts has necessitated the introduction of a duty-free product which is suitable for most industrial purposes, and at the same time is perfectly unfit for beverages or internal application. In the United Kingdom this " denaturized" alcohol is known as methylated spirit as a distinction from pure alcohol or " spirits of wine." It was first enacted in 1855 that methylated Methylated spirit, a specific mixture of pure alcohol and wood- spirlt. naphtha, should be duty-free; the present law is to be found in the Customs and Inland Revenue Act of 189o, and the Finance Act (sect. 8) of 1902. From 1858 to 1861 methylated spirit was duty-free when it was required for manufacturing processes, and the methylation or " denaturizing was carried out in accordance with a prescribed process. During the next three decades (1861-1891) the law was extended, and methylated spirit was duty-free for all purposes except for use as beverages and internal medicinal applications. This spirit (" unmineralized methylated spirit ") consisted of 90 parts of alcohol of 6o-66 over-proof (91-95 % of pure alcohol) and 10 parts of wood-naphtha. It was found, however, that certain classes were addicted to drinking this mixture, and since 1891 the sale of such spirit has been confined to manufacturers who must purchase it in bulk from the " methylators." For retail purposes the " ordinary " methylated spirit is mixed with 357 % of mineral
In Germany, the use of duty-free spirit is only allowed to state and municipal hospitals, and state scientific institutions, and for the manufacture of fulminates, fuzes and smokeless powders. The duty-free " denaturized " spirits may be divided into two groups" completely denaturized " and " incompletely denaturized." In the first category there are two varieties:(r) A mixture of roo litres of spirit and 21 litres of a mixture of 4 parts of wood-naphtha and r of pyridine bases; this spirit, the use of which is practically limited to heating and lighting purposes, may be mixed with 50 grs. of lavender or rosemary
The German regulations are apparently based on a keen appreciation of the fact that while one particular denaturizing agent may have little or no effect on one industry, yet it would be quite fatal to the success of another; there is consequently a great _ choice of denaturizing agents, and in certain cases it is sufficient to mix the alcohol with a reagent necessary for the purpose in hand, or even with a certain amount of the final product, it being only necessary to satisfy the state that the spirit is not available as a beverage. In France, the general denaturizing agent is wood-spirit of at least 58 over-proof, and containing 25 % of acetone
In America the internal revenue tax on denaturized alcohol (formerly duty-free only to scientific institutions) was removed by Congress in 1906 (act of June 7th). Pharmacology, Toxicology and Therapeutics of Alcohol. Alcohol is of great medicinal value as a solvent, being used to form solutions of alkaloids, resins, volatile oils, iodoform, &c. In strength of about xo % and upwards it is an antiseptic. If applied to the skin it rapidly evaporates, thereby cooling the skin and diminishing the amount of sweat excreted. This refrigerant and anhidrotic action is employed to soothe many forms of headache by bathing the forehead with eau de Cologne. If, on the other hand, the alcohol be rubbed into the skin, or if its evaporation be preventedas by a watch-glassit absorbs water from the tissues and thus hardens them. Thoroughly rubbed into the skin alcohol dilates the blood-vessels and produces a mild counter-irritant effect. Many alcoholic liniments are therefore employed for the relief of pain, especially muscular pains, as in lumbago and. other forms of so-called " muscular rheumatism." Given internally in small quantities and in sufficient dilution, alcohol causes dilatation of the gastric blood-vessels, increased secretion of gastric juice, and greater activity in the movements of the muscular layers in the wall
gastritis
tissue , atrophy of the gastric glands and permanent ,cessation of the gastric functions.A single dose of concentrated alcohol (e.g. brandy) produces very valuable reflex effects, the heart beating more rapidly and forcibly, and the blood-pressure rising. Hence the immediately beneficial effect produced in the cases of " fainting " or syncope. After absorption, which is very rapid, alcohol exerts a marked action upon the blood. The oxygen contained in that fluid, and destined for consumption by the tissues, is retained by the influence of alcohol in its combination with the haemoglobin or colouring matter of the red blood corpuscles. Hence the diminished oxidation of the tissues, which leads to the accumulation of unused fat and so to the obesity which is so often seen in those who habitually take much alcohol. The drug exerts a noteworthy action upon the body-temperature. As it dilates the blood-vessels of the skin it increases the subjective sensation of warmth. The actual consequence, however, is that more heat than before is necessarily lost from the surface of the body. Alcohol also diminishes the oxidation which is the main-source of the body-heat. It follows that the drug is an antipyretic, and it is hence largely used in fevers as a means of reducing the temperature. This reduction of the temperature, carried to an undesirable extreme, is the reason why the man who has copiously consumed spirits " to keep out the cold " is often visited with pneumonia. The largest amount of alcohol that can be burnt up within the healthy body in twenty-four hours is xa oz., but it must be consumed in great dilution and divided into small doses taken every four hours. Otherwise the alcohol will for the most part leave the body unused in the urine and the expired air. In fever the case is different. The raised temperature appears to facilitate the oxidation of the substance, so that quantities may be taken and completely utilized which would completely intoxicate the individual had his temperature been normal. It follows that alcohol is a food in fever, and its value in this regard is greatly increased by the fact, that it requires no primary digestion, but passes without changes, and without needing change, to the tissues which are to use it. According to Sir Thomas Fraser nothing else can compete with alcohol as a food in desperate febrile cases, and to this use must be added its antipyretic power already explained and its action as a soporific. During its administration in.febrile cases the drub must be most carefully watched, as its action may prove deleterious to the nervous system and the circulation in certain classes of patient. The state of the pulse is the best criterion of the action of alcohol in any given case of fever. The toxicology of alcohol is treated in other articles. It includes acute alcoholism (i.e. intoxication), chronic alcoholism, delirium tremens, and all the countless pathological changesextending to every tissue but the bones, and especially marked in the nervous systemwhich alcohol produces. (See DRUNKENNESS;DELIRIUM).After death the presence of alcohol can be detected in all the body fluids. Its especial affinity for the nervous system is indicated by the fact that, when all traces of it have disappeared elsewhere, it can still be detected with ease in the cerebro-spinal fluid. End of Article: ALCOHOL If you wish, you can link directly to this article.
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