Page:Encyclopædia Britannica, Ninth Edition, v. 5.djvu/694

680 CHC1 3, is a substitution-product of marsh-gas, CH 4 , from which it can be formed by the action of chlorine. It is a clear, colourless, volatile liquid, which refracts light strongly, with specific gravity of T525 at C., and vapour density 1-491. It boils at CO IG C. (Regnault), and is not frozen at a temperature of - 16 C. It has an agreeable ethereal odour, a slightly acrid and intensely sweet taste, is miscible in all proportions with alcohol, but is only slightly soluble in water. Though not ordinarily inflammable, it burns with a green flame when thrown upon hot coals, or if a light be applied to a mixture of it with not less than about 30 per cent, of alcohol. Chloroform may be employed as a solvent for resin, camphor, gutta-percha, iodine, bromine, and the alkaloids. It can be prepared in a great variety of ways : (1) By the action of alkalies on chloral (see ); (2) by boiling trichloracetic acid, CC1 3 .CO(OH), with aqueous solutions of the alkalies ; (3) by the replace ment of an atom of chlorine in carbon tetrachloride, CC1 4 , by nascent hydrogen ; (4) on the large scale for commercial purposes by the action of bleaching powder on ethylic alcohol and other carbon compounds. About 8 Bb of slaked lime, and 80 K) of the strongest chloride of lime, and 22 gallons of water at a temperature of 80-90 C. are introduced into a leaden vessel or wooden cask, and thoroughly mixed. Two ft&amp;gt; of alcohol are then poured in ; and if the heat evolved in the ensuing reaction is not sufficient to distil over the chloroform, a current of steam is passed into the vessel. The crude distillate is purified by washing with water and agitation with sulphuric acid, and by redistillation, finally, with a small quantity of slaked lime and calcium chloride, by means of a water-bath. The chief impurities to which chloroform is liable are ether, alcohol, aldehyde, hydrochloric, hypochlorous, and sulphuric acids, chloral, and heavy volatile oils. Pure chloroform does not become opalescent in contact vith water, and is not coloured yellow or brown by sulphuric acid, or green by chromic acid ; with the former, it gradually evolves hydrochloric acid. When exposed to air and light, chloro form becomes decomposed, with the formation of chlorine, hydrochloric acid, carbon tetrachloride, and other products. The presence of chloroform can be detected by adding to the liquid to be tested for it a monamine, such as aniline, N(C H 6 )H 2, and an alcoholic solution of caustic potash, when the characteristic odour of the carbamines is given off at once, or on the application of heat. The history of chloroform affords but one amongst many instances of the importance of chemical research even when no immediate practical advantages are apparently to be derived from its prosecution. Chloroform was dis covered in 1831 by Guthrie in America, and by Soubeiran in France, and by the latter was described as ether lichloriqiie. Liebig, who made the independent discovery of it in the following year, regarded it as a trichloride of carbon ; but in 1834 its true constitution was established by Durnaa. In March 1847 Flourens submitted to the Academy of Sciences at Paris a paper containing observations on the anaesthetic powers of chloroform upon animals. In the summer of that year &quot; chloric ether,&quot; the active principle of which is chloroform, was used at St Bartholomew s Hospital by Mr Lawrence instead of sulphuric ether for the production of anaesthesia ; and in the succeeding autumn Dr J. Y. Simpson of Edinburgh introduced the employment of pure chloroform as an anaesthetic into surgical practice. By its effect upon the nervous system chloroform causes a suspension of voluntary motion and of sensation, whilst respiration and the action of the sympa thetic ganglia of the heart are still continued. It is more active, occasions less bronchial irritation, and is easier of application than ether, the use of which in British practice it has to a very great extent superseded ; it possesses also the advantage that its vapour is uninflammable. The occurrence, however, from time to time, of deaths in con sequence of the use of chloroform, has led many practi tioners to recommend the employment of ether in its stead ; but in the majority of instances fatal results may be attributed to some fault in administration ; and in some cases death has been thought to be attributable to the giving of a less than customary quantity of chloroform, which, paralyzing the cerebral hemispheres, but not the ganglia of the base of the brain and the medulla, has permitted reflex action of the vagus upon the heart through irritation of a sensory nerve. In operations after which disturbance of the abdomen must be avoided, ether is far preferable to chloroform, on account of the sickness usual for some time after the taking of the latter. Snow, Ancesthetics ; Holmes, System of Surgery, 2cl ed,, vol. v. 480 (1871).  CHOCOLATE is a preparation from the seeds of the cocoa or cacao tree (Tlieobroma Cacao), used as food. The term is corrupted from the Mexican name chocolatl, and the preparation was in use in Central America before the discovery of the &quot;Western Continent by Columbus. For the history of the plant and other details see under. At the present day the general distinction between the preparations known as chocolate and cocoa respectively is that the former embraces the forms prepared as cakes or stiff paste, while prepared cocoa is chiefly sold as a powder or simply the ground nibs of the seed. Chocolate is pre pared usually from the finer varieties of cocoa seeds by first roasting, and then shelling, or depriving the seeds of their husks. They are then ground up to a very fine uniform paste on a hot plate or bed, the heat of which, by melting the fat, present in seeds to the extent of about 50 per cent, keeps the paste in a fluid condition. To the ground seeds a proportion of sugar, with sometimes arrowroot, and some flavouring essence, most commonly either vanilla or cinnamon, are added, and when thoroughly incorporated the semi-fluid paste is cast into moulds. In addition to being used as a diet drink, a very large quantity of chocolate, specially prepared under various forms for eating, is now consumed as a sweetmeat, and it forms at once a most wholesome, nutritious, and palatable confection. The French and Italians have long excelled in the manufacture of chocolate ; but the varieties made by English manufacturers are also deservedly in high repute.  CHOCTAWS, or, a North American tribe, now settled in the Indian Territory along the northern banks of the Red River, where they possess about 10,450 square miles. When first known to Europeans they occupied the district now forming the southern part of Mississippi and the western part of Alabama. On the settlement of Louisiana they formed an alliance with the French, and assisted them against the Natchez and Chickasaws ; but by degrees they entered into friendly relations with the English, and at last, in 1786, recognized the supremacy of the United States by the treaty of Hope- well. Their emigration westward began about 1800, and the last remains of their original territory were ceded in 1830. In their new settlements the Choctaws continued to advance in prosperity till the outbreak of the civil war, which considerably diminished the population and ruined a large part of their property. They sided with the Confederates, and their territory was occupied by Confeder ate troops ; and accordingly at the close of the war they were regarded as having lost their rights. Part of their land they were forced to surrender to the Government ; their slaves were emancipated ; and provision was claimed for them in the shape of either laud or money. Since then they have considerably recovered their position. In 1873 they numbered 16,000, had 50,000 acres under 