DECOMPOSI′′TION (-zĭsh′un). In chemistry, the resolution of compounds into their elements, or the alteration of their chemical constitution in such a manner that new products are formed.
DEFECA′TION. The separation of a liquid from its lees, dregs, or impurities by subsidence and decantation. It is commonly employed for the purification of saline solutions
and glutinous or unctuous liquids on the large scale in preference to filtration; than which it is both more expeditious and expensive. See Clarification, Decantation, Filtration, &c.
DEFLAGRA′TION. The sudden combustion of any substance for the purpose of producing some change in its composition, by the joint action of heat and oxygen. The process is commonly performed by projecting into a red-hot crucible, in small portions at a time, a mixture of nitrate of potash, and the body to be oxidised.
DELIQUES′CENCE. Spontaneous liquefaction by absorption of the moisture of the atmosphere. Deliquescent salts are those which by exposure gradually assume the liquid state. They should all be kept in well-closed bottles or jars.
DELIR′IUM TRE′MENS. [L.] The madness of drunkards; a disease of the brain resulting from the excessive and protracted use of intoxicating liquors, particularly of ardent spirits. The early symptoms are extreme irritability and fretfulness, with unusual mobility of the body. Sleeplessness and unpleasant dreams soon follow. At length frightful dreams and visions harass the patient. He sees remarkable sights, hears extraordinary sounds, and labours under all the strange delusions of insane persons, which, however vague and unfounded, operate on him with all the force of realities till he becomes furiously mad. The fit almost always comes on after hard drinking; and the hands are usually, but not always, tremulous. A similar affection is occasionally produced by the abuse of opium, excessive mental anxiety, night watching, or depletion. According to Dr Armstrong, even respiring the fumes of ardent spirits will, under some circumstances, produce this disease. Persons who have undergone surgical operations under the influence of chloroform are more liable to attacks of this kind than other persons.
The treatment of delirium tremens consists mainly in the judicious use of opium, laudanum, or morphia, in rather large doses, frequently repeated. Thirty to sixty drops of laudanum may be given every hour or two during the fit, its effects being carefully watched. The object is to produce quiet sleep, from which the patient usually wakes free from the worst symptoms of the disease. Diaphoretics and mild aperients may also be given, and a light, nutritious diet adopted throughout. Depletion, especially bleeding, should be particularly avoided. Alcoholic stimulants and wine, in certain cases, have proved useful. Under this treatment, the patient, unless of a very bad habit of body, or much debilitated by previous excesses, usually recovers. He is, however, very liable to relapses and subsequent attacks, which are best prevented by judicious moral management.
The judicious administration of chloral hydrate, in doses of from thirty to sixty grains as well as of bromide of potassium in twenty-grain doses, either alone or combined with the chloral, has lately been had recourse to with the happiest results, for the production of sleep in cases of delirium tremens or in the insomnia of dipsomaniacs.
The repetition of the dose of chloral requires to be regulated with very great caution; and it is only in the case of emigrants and others unable to obtain medical aid that we would recommend it to be given, and then only should opium have failed to produce the desired effect. Not more than sixty grains of the chloral should be administered during the twenty-four hours. The internal administration of tincture of capsicum in moderately large doses, in the intervals of the opiates or chloral hydrate, has lately been tried in the treatment of this disease, it is said, with success.
DELPHIN′IC ACID. Syn. Phoce′nic acid. A fatty acid, obtained by saponifying the oil of the delphinus or porpoise. According to recent experiments, it is identical with valeric acid.