4275. Tests for the Purity of Chloroform

4275.    Tests for the Purity of Chloroform. Its specific gravity should not be less than 1.490, nor more than 1.494; and should boil at 140° Fahr. When dropped into water, it sinks in transparent globules without milkiness. When mixed in a bottle with an equal bulk of sulphuric acid, it should produce no warmth; and after standing for 24 hours, neither liquid should be discolored, or, at most, a faint yellow tinge imparted to the lower or acid stratum; more discoloration than this would denote the presence of em-pyreumatic oily matter. "When evaporated on a porcelain plate, it leaves behind a slightly aromatic odor, but free from pungency.

4276. Chloral

4276.    Chloral. Chloral is an oily liquid, possessing an ethereal smell; it is soluble in alcohol, ether, and water, but its solution in the latter rapidly changes into a semisolid crystalline mass of hydrate of chloral, soluble in a larger quantity of water. Chloral boils at 202°, and has a specific gravity of 1.502.

4277. To Obtain Chloral

4277.    To Obtain Chloral. Place anhydrous alcohol in a tubulated retort, and pass dry chlorine gas through it, at first in the cold, but afterwards with the application of a gentle heat. As soon as the chlorine passes undecomposed through the liquor at the boiling temperature, the process is complete. On cooling, the liquid in the retort solidifies, forming a crystalline mass of hydra-ted chloral. This must be melted by gentle heat, and agitated with thrice its volume of oil of vitriol, when, on increasing the heat a little, an oily stratum of impure chloral will rise to the surface. This must be removed, boiled for some time, to drive off some free hydrochloric acid and alcohol, and next distilled with an equal volume of oil of vitriol; lastly, it must be rectified from finely-powdered quicklime, stopping the process as soon as the surface of the lime becomes dry. The chlorine is best introduced by a tube inserted into the tubulature of the retort, and a long tube, bent upwards, should be connected with the beak to convey away the hydrochloric acid gas extricated, and to allow the volatilized alcohol and chloral to condense and flow back into the retort.

4278. To Purify Hydrate of Chloral

4278. To Purify Hydrate of Chloral. There is perhaps scarcely a liquid in which chloral hydrate is insoluble at ordinary temperature; four parts of it dissolve gradually in one part of water, the solution crystallizes at 32° Fahr., but not in well-formed crystals. Alcohol and ether dissolve it to such an extent that it likewise does not crystallize well on evaporating these solvents; absolute alcohol must be excluded, because it combines with chloral. Chloroform and benzole are well adapted for recrystallization, but the first is too dear, and the last cannot be entirely removed from the crystals. The same holds good for most other liquid solvents, but uniformly satisfactory results are obtained with bisulphide of carbon; 45 parts of it dissolve at 60° to 65° Fahr., but 1 part chloral hydrate; it precipitates ethereal and alcoholic solutions of the latter. But at temperatures below the boiling of bisulphide of carbon, 4 to 5 parts of it are sufficient for dissolving 1 part chloral hydrate. If allowed to cool slowly, beautiful crystals, often an inch in length, are obtained, easily collected, and readily freed from the last traces of the solvent by exposing them in thin layers to the air. (Fluckiger.)