of the gastric blood-vessels, increased secretion of gastric juice, and greater activity in the movements of the muscular layers in the wall of the stomach. It also tends to lessen the sensibility of the stomach and so may relieve gastric pain. In a 50% solution or stronger—as when neat whisky is taken—alcohol precipitates the pepsin which is an essential of gastric digestion, and thereby arrests this process. The desirable effects produced by alcohol on the stomach are worth obtaining only in cases of acute diseases. In chronic disease and in health the use of alcohol as an aid to digestion is without the support of clinical or laboratory experience, the beneficial action being at least neutralized by undesirable effects produced elsewhere. The continued use of large doses of alcohol produces chronic gastritis, in which the continued irritation has led to overgrowth of connective 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 112 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 drug 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 changes—extending to every tissue but the bones, and especially marked in the nervous system—which 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.
ALCOHOLS, in organic chemistry, a class of compounds which may be considered as derived from hydrocarbons by the replacement of one or more hydrogen atoms by hydroxyl groups. It is convenient to restrict the term to compounds in which the hydroxyl group is attached to an aliphatic residue; this excludes such compounds as the hydroxy-benzenes, naphthalenes, &c., which exhibit many differences from the compounds derived from the aliphatic alkyls.
Alcohols are classified on two distinct principles, one depending upon the number of hydroxyl groups present, the other on the nature of the remaining groups attached to the carbon atom which carries the hydroxyl group. Monatomic or monohydric alcohols contain only one hydroxyl group; diatomic, two, known as glycols (q.v.); triatomic, three, known as glycerols (q.v.); and so on.
The second principle leads to alcohols of three distinct types, known as primary, secondary and tertiary. The genesis and formulation of these types may be readily understood by considering the relation which exists between the alcohols and the parent hydrocarbon. In methane, CH4, the hydrogen atoms are of equal value, and hence only one alcohol, viz. CH3OH, can be derived from it. This compound, methyl alcohol, is the simplest primary alcohol, and it is characterized by the grouping ·CH2OH. Ethane, C2H6, in a similar manner, can only give rise to one alcohol, namely ethyl alcohol, CH3CH2OH, which is also primary. Propane, CH3CH2CH3, can give rise to two alcohols—a primary alcohol, CH3CH2CH2OH (normal propyl alcohol), formed by replacing a hydrogen atom attached to a terminal carbon atom, and a secondary alcohol, CH3·CH(OH)·CH3 (isopropyl alcohol), when the substitution is effected on the middle carbon atom. The grouping CH·OH characterizes the secondary alcohols; isopropyl alcohol is the simplest member of this class. Butane, C4H10, exists in the two isomeric forms—normal butane, CH3·CH2·CH2·CH3, and iso-butane, CH(CH3)3. Each of these hydro-carbons gives rise to two alcohols: n-butane gives a primary and a secondary; and iso-butane a primary, when the substitution takes place in one of the methyl groups, and a tertiary, when the hydrogen atom of the ⫶CH group is substituted. Tertiary alcohols are thus seen to be characterized by the group ⫶C·OH, in which the residual valencies of the carbon atom are attached to alkyl groups.
In 1860 Hermann Kolbe predicted the existence of secondary and tertiary alcohols from theoretical considerations. Regarding methyl alcohol, for which he proposed the name carbinol, as the simplest alcohol, he showed that by replacing one hydrogen atom of the methyl group by an alkyl residue, compounds of the general formula R·CH2·OH would result. These are the primary alcohols. By replacing two of the hydrogen atoms, either by the same or different alkyls, compounds of the formula (R·R1)CH·OH (i.e. secondary alcohols) would result; while the replacement of the three hydrogen atoms would generate alcohols of the general formula (R·R1·R2)C·OH, i.e. tertiary alcohols. Furthermore, he exhibited a comparison between these three types of alcohols and the amines. Thus:—
| R·NH2 | (R1R2)NH | (R1R2R3)N |
| R·CH2OH | (R1R2)CH·OH | (R1R2R3)C·OH |
| Primary. | Secondary. | Tertiary. |
To distinguish Primary, Secondary and Tertiary Alcohols.—Many reactions serve to distinguish these three types of alcohols. Of chief importance is their behaviour on oxidation. The primary alcohols are first oxidized to aldehydes (q.v.), which, on further oxidation, yield acids containing the same number of carbon atoms as in the original alcohol. Secondary alcohols yield ketones (q.v.), which are subsequently oxidized to a mixture of two acids, Tertiary alcohols yield neither aldehydes nor ketones, but a mixture of two or more acids. Another method is based upon the different behaviour of the corresponding nitro-alkyl with nitrous acid. The alcohol is first acted upon with phosphorus and iodine, and the resulting alkyl iodide is treated with silver nitrite, which gives the corresponding nitro-alkyl. The nitro-alkyl is then treated with potassium nitrite dissolved in concentrated potash, and sulphuric acid is added. By this treatment a primary nitro-alkyl yields a nitrolic acid, the potassium salt of which forms an intense red solution; a secondary nitro-alkyl forms a pseudo nitrol, which gives an
