Formula, - C2Hci3oh2o.

Derivation

Chloral is obtained by the action of dry chlorine gas on absolute alcohol, and is purified by sulphuric acid and a small quantity of lime ; a small quantity of water converts it into solid crystalline hydrate of chloral. It is in the form of a snow-white, crystalline mass, with a pungent odor and taste, soluble in its own weight of distilled water, and very soluble in alcohol. When heated, it fuses and evaporates, leaving no residue, and in the air without combustion.

Medical Properties And Action

Hydrate of chloral is hypnotic and anaesthetic, possessing more of the former and less of the latter property than chloroform, and, unlike chloroform, after its administration there is no elimination by the breath or urine. It diffuses into the blood rapidly, causing an abundant flow of saliva, and a cooling sensation in the stomach, followed by warmth. Very large quantities cause a high degree of gastric irritation, nausea and vomiting; very large doses of chloral paralyze the heart, and produce a fall of arterial pressure, and a slow, feeble, or sometimes a rapid running pulse. The blood becomes dark and grumous-looking with the corpuscles broken down. Taken in moderate quantity it stimulates the appetite, and produces muscular relaxation. It is uniformly certain in its action as a hypnotic, has no depressing influence, and does not cause constipation. Administered in doses of gr. x to gr. xxx, it causes unconsciousness to pain, and a profound sleep, lasting over several hours. The sleep it produces is quiet and gentle, and induced without distress. Liebreich claims to have produced sleep which lasted from five to fifteen hours, with from 25 to 30 grains of hydrate of chloral.

The habitual use of chloral leads to a disorder which is somewhat similar to the "opium habit," although it may not be as persistent. When there is present no susceptibility to its hypnotic action, it is liable to cause headache, and in some cases, a delirious excitement. Its hypnotic action is immediately preceded by a stage of excitement, generally of short duration, which is followed by sudden and complete sleep, very much like natural sleep, calm, dreamless and refreshing. It differs from a condition of narcotism from the fact that the patient can be easily roused to partake of nourishment, and will readily fall asleep again.

There are no unpleasant after-effects resulting from a moderate dose of chloral, differing in this respect from morphine, which often causes headache, faintness, giddiness, nausea and constipation. Chloral is not capable of producing insensibility to pain, unless the quantity administered is sufficient to suspend the functions of the cerebrum. Great care is necessary in its use where symptoms of pulmonary disease, fatty-heart or degenerated blood vessels are apparent.

When a proper dose is administered the pupil contracts slightly, but the pulse may remain unaltered or become slower, and the respiration unaffected. When an improper or dangerous dose is taken, profound narcotism ensues, the respiration becomes slower, the pulse weak, rapid and irregular, sensibility is lost, all reflex movements are impossible, and complete muscular relaxation follows. It destroys life by the suspension of the functions of the cerebrum, and by paralysis of the respiratory centre, and of the cardiac ganglia; also death may suddenly follow by paralysis of the heart, in cases of fatty degeneration, and the lower lobes of the brain remain unaffected. The paralytic phenomena caused by chloral are due to its direct action on the nervous centres. The congestion of the meninges of the brain and cord, and distension of the right cavities of the heart, have been observed after poisoning by chloral. The antidote in cases of poisoning is strychnia, and the same treatment as in opium poisoning.

Therapeutic Uses

The most important uses of chloral are in diseases of the nervous system, such as delirium tremens, insanity, tetanus, acute mania, neuralgia, chorea, whooping-cough, and in rheumatism, cholera morbus, seasickness, etc., etc. Having no direct pain-relieving power, except by suspending the functions of the cerebrum and in dangerous doses, sleep can be procured and pain relieved by combining the chloral with morphine, when it is very effective.