Chloral. Hydrate of chloral. Chloral, Fr.; Chloralhydrat, Ger.

Separate, rhomboidal, colorless and transparent crystals, slowly evaporating when exposed to the air, having an aromatic, penetrating, and slightly acrid odor, a bitterish, caustic taste, and a neutral reaction. Freely soluble in water, alcohol, or ether; also soluble in four parts of chloroform, in glycerin, benzol, benzin, disulphide of carbon, fixed or volatile oils. It liquefies when mixed with carbolic acid and camphor.


, grs. vЭ), or more, but it should not be forgotten that 3 ss has produced toxic symptoms.

Antagonists and Incompatibles

The depression of the heart and respiration caused by chloral is antagonized by alcoholic stimulants, ammonia, atropine, by galvanism, and by artificial heat. These are, therefore, appropriate remedies to be employed in cases of poisoning. Strychnine is held by Liebreich to be antagonistic, and hence it may be administered hypodermatically when the measures above mentioned are being used.

Alkalies decompose chloral with the production of formic acid and chloroform, hence all agents having an alkaline reaction are incompatible.


The hypnotic medicines, notably opium, and the anaesthetics, deepen the effects of chloral when they are simultaneously administered.

Physiological Actions

Chloral has considerable antiseptic property, and is preservative of animal textures. It produces redness and inflammation of the skin, when kept in contact with it for a lengthened period. The taste of chloral is hot and pungent, and it excites an abundant flow of saliva. In the stomach it causes first a cooling sensation, followed by warmth, and when taken in large quantity may set up a high degree of gastric irritation, nausea, and vomiting. In moderate quantity chloral rather stimulates than impairs the appetite, and indigestion and nausea do not, as a rule, follow as an after-effect.

Chloral diffuses into the blood rapidly. The changes which occur after its entrance into the vessels are much disputed. Liebreich, as is well known, was led—by observing the reaction when chloral is brought into the presence of an alkali—to the deduction that the soda of the blood would split up chloral into chloroform and formic acid, and that, therefore, the effects belonging to chloroform might be produced by the administration of chloral. It is probably true that this reaction does take place to some extent, but there are several insuperable objections to the theory of Liebreich:

1.  The effects of chloral differ from those produced by a corresponding quantity of chloroform.

2.  After the administration of chloral, there is no elimination of chloroform by the breath or urine

3.   Chloral is more decidedly hypnotic, and much less anaesthetic, than chloroform.

4.   Crystals of chloral have been recognized in the blood, and the products of the decomposition of chloral have recently been recovered from the urine.

The effects which follow an ordinary medicinal dose (fifteen to thirty grains) are not the same in all subjects, although it must be admitted that a great degree of uniformity exists. When there is present an insusceptibility to its hypnotic action it produces headache, and in some subjects a delirious excitement. Immediately preceding its hypnotic action there is developed in all subjects a stage of excitement, usually very short in duration, and followed by sudden and complete sopor. The sleep produced by chloral is extraordinarily like natural sleep, and is calm, dreamless, and refreshing. It is not a condition of narcotism, and the patient may be easily aroused to take food and nourishment, and will quickly and without difficulty fall asleep again. As a rule no unpleasant after-effects are experienced from a dose of chloral—no headache, faintness, giddiness, nausea, and constipation, so common after morphine. The quantity of chloral necessary to produce sleep, without dangerous narcotism, ranges from fifteen to forty grains, and the duration of the effect varies in different subjects from two to eight hours. Chloral does not destroy the sensibility to pain, unless administered in a quantity sufficient to suspend the functions of the cerebrum. It is not a pain-relieving agent in the sense that morphine is.

When sleep is produced by proper medicinal doses of chloral the pupil contracts a little, the pulse may remain unaltered or become slower, and the respirations are unaffected. When a dangerous or lethal dose is taken, profound narcotism will follow; the respirations will be slower and shallower, the pulse will become weak, rapid, and irregular; sensibility and the reflex movements will be abolished, and complete muscular relaxation will ensue. The mode of dying is by suspension of the functions of the cerebrum, and, finally, by paralysis of the respiratory center, and of the cardiac motor ganglia. Death may be suddenly produced by paralysis of the heart, in cases of fatty degeneration of the muscular tissue of this organ, without proceeding so far as to involve the lower centers of the brain.

A marked reduction in temperature, notably in rabbits—so much as 8° Fahr.—is produced by chloral, but this effect may be considerably lessened by enveloping the body in non-conductors (Brunton), which act by preventing the cooling of the blood by the atmosphere. The first effect of chloral is to raise the arterial tension (stage of excitement), but this action quickly ceases, and a decided lowering of the tension results. The diminished arterial tension and the weakened action of the heart are the principal factors in the reduction of the body temperature, for the combined action of these agencies is to lessen the combustion process. After death from chloral, congestion of the meninges of the brain and cord, of the lungs, and distention of the right cavities of the heart, have been observed. The arrest of the heart's action takes place in the diastole.

Chloral does not affect the motor nerves nor impair the contractility of muscle; hence the paralytic phenomena both of animal and of organic life produced by it are due to its direct action on the nervous centers.

Very large quantities of chloral have been taken without producing fatal symptoms. I have seen a patient who took daily from two drachms to three drachms of chloral for many months, without any symptoms of acute poisoning. While it is true that enormous doses (several hundred grains) have been taken without producing lethal effects, it is equally true that serious symptoms and death have resulted from very moderate doses (twenty to thirty grains). Great care should therefore be taken in prescribing an agent of such uncertain power. A fatty heart, atheromatous degeneration of the vessels, advanced disease of the lungs, and instability of the nervous system, are contraindications of the use of chloral.