These correspond to haloid salts of metals, e.g.:

Potassium Bromide.

KBr.

Ethyl Bromide.

(C2H5)Br.

aethyl Bromidum. Bromide of Ethyl. C2H5Br. Hydro-bromic Ether. Not officinal.

Characters. - A colourless volatile liquid; of peculiar odour and sweetish taste. Specific gravity, 1.419.

Preparation. - By distilling alcohol with bromide and phosphorus.

Action and Uses. - When applied as spray it produces local anaesthesia, which seems to depend on the action of the drug on the nerves as well as on the cold produced. It is used as a local anaesthetic in neuralgia. When inhaled it produces anaesthesia, and has been recommended as an anaesthetic either alone or as a mixture of one part of it with 3 of chloroform and 4 of alcohol. Its advantages are that it is not inflammable like ether, that it does not irritate the respiratory passages, and that it causes less excitement and struggling than ether or chloroform, and is less depressing than chloroform. Its disadvantages are that it is not absolutely safe, as one death at least has occurred from its use. Its odour remains longer in the breath than either chloroform or ether, and some patients dislike its smell extremely.

aethyl Iodidum. Iodide of Ethyl. C2H5I. (Hydriodic Ether.) Not officinal.

Characters. - A colourless liquid, with a penetrating odour. It is apt to become decomposed by keeping, and acquire a brown colour from free iodine.

Preparation. - Like bromide of ethyl, using iodine instead of bromine.

Action and Uses. - It has an anaesthetic action when inhaled, which is more slowly produced but is more persistent than that of ethyl bromide. It is decomposed in the body, and the iodine is excreted in the urine as iodide of potassium. It has been given internally as an alterative in doses of 0.2 to 0.5 gm. in scrofula and rheumatism, and as a diuretic in cases of cardiac dropsy. Its chief use, however, is as an antispasmodic in asthmatic paroxysms, either of the purely spasmodic kind, or occurring in chronic bronchitis and emphysema, or in cardiac or laryngeal disease. In some of these cases it gives very great relief, and not only cuts short the paroxysm, but benefits the bronchitic condition where this is present (cf. p. 562).

Administration. - It is best given in small glass capsules containing 5 minims, and encased in cotton-wool and silk. These can be readily carried about, and when the paroxysm comes on one is crushed between the finger and thumb, and the vapour inhaled from the cotton-wool, which becomes soaked by the iodide.

Chloral Hydras, B.P.; Chloral, U.S.P. C2HC13O.H2O; 165.2. Hydrate of Chloral (Hydrous Chloral), B.P. Chloral, U.S.P.

Characters. - Whitish crystals with a peculiar very pungent odour, a bitterish caustic taste, and a neutral reaction. It melts when heated, forming a colourless liquid, and volatilises if the temperature be further raised.

Preparation. - By saturating absolute alcohol with dry chlorine gas much hydrochloric acid gas is formed, and the alcohol is first reduced to aldehyd, which is then attacked by the chlorine, forming trichloraldehyd, a word which has been shortened to chloral. Chloral is an oily liquid, which is purified with sulphuric acid, and then with lime, and finally converted into hydrous chloral by the addition of water.

Solubility. - It is soluble in less than its own weight of water, alcohol, or ether, and in four parts of chloroform.

Reactions. - When mixed with carbolic acid or camphor it liquefies. When mixed with alkalis it is decomposed into chloroform and a formiate of the base.

Impurities. - Hydrochloric acid and oily impurities.

Test. - The aqueous solution should be neutral or only slightly acid. A solution in chloroform when shaken with sulphuric acid should not impart colour to the acid (absence of oily impurities).

Preparation

B.P.

Dose.

Syrupus Chloral. Syrup of Chloral. Chloral in syrup and water, 10 grs. in each fl. dr...........................................................

1 fl. dr.

Action of Anhydrous Chloral. - Anhydrous chloral applied to the skin is absorbed and converted in the organism into chloral hydrate. When thus applied it sometimes occasions haemoglobinuria and nephritis. Anhydrous chloral being little used, the name 'chloral' is applied in ordinary conversation to chloral hydrate, and in the following account of the action of chloral hydrate the name chloral is intended to apply to the hydrate.

Action of Chloral Hydrate. - It destroys low organisms, and prevents the decomposition which they occasion. It is therefore sometimes used as an antiseptic. In the mouth chloral has a hot, burning taste, and when applied to a raw surface, or to the mucous membrane of the eye, it is a powerful irritant. When injected under the skin in a strong solution it is apt to cause inflammation and suppuration. It was introduced into medicine by Oscar Liebreich with the object of attaining by it the same effects as those of chloroform slowly administered for a length of time. When chloral is mixed with an alkali it is split up, yielding formic acid which combines with the alkali and chloroform. Liebreich thought that if chloral were administered internally the alkalis of the blood would slowly split it up, and that chloroform would thus be slowly generated from it in the circulating blood for a considerable length of time. His expectations regarding the utility of chloral as a means of producing sleep and relieving pain have been fully answered; but the theory which led him to employ chloral appears to be erroneous, and it probably acts as a hypnotic and analgesic without undergoing any decomposition in the body. The experiments which have led to the conclusion that chloral is not decomposed in the body are chiefly those of Hammersten, who found that when a stream of carbonic acid was passed through the blood taken from chloralised animals, and then passed through a red-hot tube into a mixture of starch paste and iodine or a solution of nitrate of silver, no reaction occurred, and that the slightest addition of chloroform to the blood or the administration of chloroform to the animal beforehand always causes a reaction to take place. The expired air of chloralised animals is also free from chloroform. The chloral is excreted in the urine as such so long as the urine is acid, and it is only when the urine is alkaline that chloroform is found in it, this being formed by the decomposition of the chloral by the alkali in the urine itself. In frogs, small doses slow the respiration, and abolish reflex action, but the animal recovers perfectly after several hours. When the dose is increased, the stoppage of the heart follows the cessation of reflex movements and the animal dies. In mammals, the respiration also becomes slow, the pupil contracted, and sleep occurs. From this the animal may first be awakened with ease, but it gradually becomes deeper, and the reflex movements disappear. Insensibility occurs first to painful impressions, so that the animal may be cut or burned without showing the slightest symptoms of sensation, whereas it will still withdraw its limb quickly when a slight pressure is made upon the toes. When larger doses are given, the temperature gradually falls until it can no longer be measured by an ordinary clinical thermometer. The respiration gets slower and weaker, and finally ceases altogether. When chloral is added to the blood, it causes the red corpuscles to swell up and become paler, but does not dissolve them.