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CHLORAL

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Originally appearing in Volume V06, Page 254 of the 1911 Encyclopedia Britannica.
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CHLORAL , orTRICHLORACETALDEHYDE, CC13• CHO, a substance discovered by J. von See also:

Liebig in 1832 (See also:Ann., 1832, 1, p. 189) and further studied by J. B. A. See also:Dumas and Staedeler. It is a heavy, oily and colourless liquid, of specific gravity 1.541 at o° C., and boiling-point 97.7° C. It has a greasy, somewhat See also:bitter See also:taste, and gives off a vapour at See also:ordinary temperature which has a pungent odour and an irritating effect on the eyes. The word chloral is derived from the first syllables of See also:chlorine and See also:alcohol, the names of the substances employed for its preparation. Chloral is soluble in alcohol and See also:ether, in less than its own See also:weight of See also:water, and in four times its weight of See also:chloroform; it absorbs chlorine, and dissolves See also:bromine, See also:iodine, See also:phosphorus and See also:sulphur. Chloral deliquesces in the See also:air, and is converted by water into a See also:hydrate, with See also:evolution of See also:heat; it combines with See also:alcohols and See also:mercaptans. An ammoniacal See also:solution of See also:silver nitrate is reduced by chloral; and nascent See also:hydrogen converts it into aldehyde. By means of phosphorus pentachloride, chlorine can be substituted for the See also:oxygen of chloral, the See also:body CC13•CC12H being produced; an analogous See also:compound, CC13•C(See also:C6H6)2H, is obtained by treating chloral with See also:benzene and sulphuric See also:acid.

With an See also:

alkali, chloral gives chloroform (q.v.) and a formate; oxidizing agents give trichloraceticacid, CC13• CO (OH). When kept for some days, as also when placed in contact with sulphuric acid or a very small quantity of water, chloral undergoes spontaneous See also:change into the polymeride metachloral (C2C13OH)3, a See also:white porcell.aneous body, slowly volatile in the air, and reconverted into chloral without melting at 18o° C. Chloral unites directly with hydrocyanic acid to See also:form 0-trichloracetonitrile, CC13• CH(OH) CN, and with hydroxyl-amine it forms chlorglyoxime, C2H3C1N202. Chloral is prepared by passing dry chlorine into See also:absolute alcohol; the latter must be cooled at first, but towards the end of the operation has to be heated nearly to boiling. The alcohol is converted finally into a syrupy fluid, from which chloral is procured by treatment with sulphuric acid (see P. Fritsch, Ann., 1894, pp. 279, 288). The crude chloral is distilled over See also:lime, and is purified by further treatment with sulphuric acid, and by redistillation. A mixture of See also:starch or See also:sugar with See also:manganese peroxide and hydrochloric acid may be employed instead of alcohol and chlorine for the manufacture of chloral (A. Staedeler, Ann. Ch. Pharm., 1847, 61, p.

Tor). An isomer of chloral, parachloralide, is made by passing excess of dry chlorine into absolute methyl alcohol. Chloral hydrate, CCl3•CH(OH)2, forms oblique, often very See also:

short, rhombic prisms. The crystals are perfectly transparent, only slightly odorous, See also:free from See also:powder, and dry to the See also:touch, and do not become white by exposure. The melting-point of pure chloral hydrate is 57°, the boiling-point 96-98° C. When heated with sulphuric acid it is converted into anhydrous chloral and chloralide, C6H2CI6O3. When mixed with water, chloral hydrate causes a considerable degree of See also:cold; and, as with camphor, small fragments of it placed on the See also:surface of water exhibit gyratory movements. Chloral hydrate does not restore the See also:colour to a solution of See also:fuchsine which has been decolorized by sulphurous acid, and so one must assume that the water See also:present is combined in the molecular See also:condition (V. See also:Meyer, See also:Bee., 188o, 13, p. 2343). Chloral may be estimated by distilling the hydrate with See also:milk of lime and measuring the See also:volume of chloroform produced (C. H.

See also:

Wood, Pharm. Journ., (3) I, p. 703), or by See also:hydrolysis with a known volume of See also:standard alkali and back titration with standard acid (V. Meyer, Bee., 1873, 6, p. 600). Chloral hydrate has the See also:property of checking the decomposition of a See also:great number of albuminous substances, such as milk and See also:meat and a mixture of it with See also:glycerin, according to J. Personne, is suitable for the preservation of anatomical preparations. When heated with concentrated glycerin to a temperature of no° to 230° C., chloral hydrate yields chloroform, CHCI3, and allyl formate,HCO(OCaHa)• See also:Pharmacology and See also:Therapeutics.—The breaking up of chloral hydrate, in the presence of alkalis, with the See also:production of chloroform and formates, led Liebreich to the conjecture that a similar decomposition might be produced in the See also:blood; and hence his introduction of the See also:drug, in 1869, as an anaesthetic and hypnotic. It is now known, however, that the drug circulates in the blood unchanged, and is excreted in the form of urochloralic acid. The dose is from five to twenty grains or somewhat more, and it is often given in the form of the pharmacopoeial See also:Syrup-us Chloral, which contains ten grains of chloral hydrate to the fluid drachm. Chloral hydrate must be well diluted when given by the mouth, as otherwise it may cause considerable gastro-intestinal irritation. In large doses chloral hydrate is a depressant to the circulation and the respiration, and also lowers the temperature.

In the above doses the drug is a powerful and safe hypnotic, acting directly on the See also:

brain, and producing no preliminary See also:stage of excitement. Very soon—perhaps twenty minutes--after taking such a dose, the patient falls into a See also:sleep which lasts several See also:hours, and is not distinguishable from natural sleep. When he wakes, it is without disagreeable after-symptoms, but with a feeling of natural refreshment. The pupils are always contracted under its See also:influence, except in large doses. There is also rapidly induced a depression of the anterior horns of See also:grey See also:matter in the See also:spinal See also:cord, and as the symptoms of See also:strychnine poisoning are due to violent stimulation of these areas, chloral hydrate is a valuable antidote in such cases. It should not be hypodermically injected. Its disadvantages are that it is powerless when there is See also:pain, resembling in this feature nearly all hypnotics except See also:opium (See also:morphine) and hyoscin. Its See also:action on the gastro-intestinal See also:canal and on the See also:respiratory and circulatory systems renders its use inadvisable when disease of these See also:organs is present. Its action on the spinal cord has been employed with success in cases of See also:tetanus, whooping-cough, urinary incontinence, and strychnine poisoning. In the latter See also:case twenty grains in " normal saline " solution may be directly injected into a subcutaneous vein, but not into the subcutaneous tissues. See also:Toxicology.—In cases of acute poisoning by chloral hydrate, the symptoms may be summarized as those of profound See also:coma. The treatment is to give a stimulant emetic such as See also:mustard ; to keep up the temperature by hot bottles, &c.; to prevent or disturb the patient's morbid sleep by the injection of hot strong See also:coffee into the rectum:, and by shouting, flipping with towels, &c.; to use artificial respiration in extreme cases; and to inject strychnine.

Strychnine is much less likely, however, to See also:

save See also:life after poisoning by chloral hydrate, than chloral hydrate is to save lite in poisoning by strychnine. Chronic poisoning by chloral is a most pernicious drug-See also:habit. The See also:vice is easily and very rapidly acquired. The victim is usually excited and loquacious. He is easily fatigued and suffers from attacks of easily induced See also:syncope. There are signs of gastro-intestinal irritation, and a tendency to cutaneous eruptions of an erythematous type. The patient may succumb to a dose only slightly larger than usual. The treatment is on See also:general principles, there being no specific remedy. The patient must be persuaded to put himself under See also:restraint, and the drug must be stopped at once and entirely.

End of Article: CHLORAL

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