to start the process the mixture is gently heated. A violent reaction sets in with the formation of a dark brown syrupy liquid. If the reaction proceeds too violently the flask is cooled in water. The product is again heated, when a second less violent reaction occurs and a light yellow liquid is produced, which on cooling solidifies to a crystalline mass. From this, iodpropionic acid may be extracted with hot carbon bisulphide or petroleum ether. On distilling off the solvent a discoloured residue remains, from which the acid may be obtained in colourless crystals by recrystallisation from carbon bisulphide. CH2(OH).CH(OH).COOH+3HI=CH2I.CH2.COOH + 2H2O Glycer.c Acid B-lodpropion.c Acid. + 21 Properties. Colourless pearly laminae; m. p. 83'5°; slightly soluble in cold, readily in hot water and in alcohol. PREPARATION LXXVIII. a-PROPENYL DICHLORHYDRIN, C2H&Cl2O= CH2CI.CH(OH).CH2Cl LITERATURE.-Berthelot (1854) Ann. Ch. Phys. (3) 41, 296; Reboul (1860), Ann. Ch. Phys. (3) 60, 1; Carius (1862), Ann. Ch. Pharm. 122, 73; Claus (1873), Ann Ch. Pharm. 168, 42. 100 grms. anhydrous glycerin. 250 chloride of sulphur. (See p. 114.) Two hundred and fifty grms. chloride of sulphur are slowly added in small quantities from a tap funnel to 100 grms. anhydrous glycerin (dehydrated at 175°) contained in a retort, which is connected with a reflux condenser.* During the process the contents of the retort are well shaken. The reaction is completed on the brine-bath until the evolution of hydrochloric acid has nearly ceased. The condenser is now removed, and the mass again heated until all sulphur dioxide and hydrochloric acid are expelled. The product of the reaction which becomes semi-solid on cooling is extracted with 2-3 times the volume of ether. The ethereal solution is filtered from sulphur and the ether distilled. A liquid remains which may be purified by repeated rectification. CH2OH.CH(OH).CH(OH) + 2S2Cl2 = CH,CI.CH(OH). CH,C1+ 2HC1+SO2+3S Properties.-Colourless liquid with an ethereal smell; b. p. 175.8—176·3°; sp. gr. 1*383 at 0°. M LITERATURE.-Wöhler (1828), Pogg. Ann. 12, 253, Berz. Jahresb. 12, 226; Clemm (1848), Ann. Ch. Pharm. 66, 382. 100 grms. anhydrous potassium ferrocyanide.1 187 red oxide of lead. neutral ammonium sulphate.2 One hundred grms. carefully dehydrated potassium ferrocyanide and 375 grms. anhydrous potassium carbonate are well mixed, and the mixture heated in a covered iron crucible, in a charcoal furnace, until it fuses quietly without the application of too strong a heat. To the cooled, but still liquid mass 300 grms. dry red oxide of lead are gradually added in small quantities, and the whole again fused for a time. When the reduced lead has collected at the bottom of the vessel, the liquid mass is poured off on to an iron plate and allowed to cool. It solidifies and is broken up. It is then dissolved in about 200 c.c. 1 Potassium ferrocyanide (K4FeСу6 + 3H2O) is dehydrated by heating the powdered salt on an iron tray over a small flame with constant stirring. 2 Commercial ammonium sulphate has usually a slightly acid reaction, and must therefore be neutralised with ammonia. water, the aqueous solution of potassium cyanate filtered, and a concentrated solution of 100 grms. neutral ammonium sulphate added to the filtrate. The liquid is evaporated to a small bulk on the waterbath, and on cooling, the crystallised potassium sulphate separated from the mother liquor. The filtrate is evaporated to dryness, and the cooled residue extracted with absolute alcohol, which dissolves out the urea. On distilling off the alcohol, the solid greenish residue is purified by recrystallisation from alcohol with the addition of animal charcoal. 4K4FeСy+4K2CO3+5Pb3O4=15Pb+24KCNO+4CO+4FeO Potassium Lead Oxide Potassium Properties.-Colourless prisms; m. p. 131°, easily soluble in water, scarcely soluble in ether. (Thiocarbamide, Sulphourea.) LITERATURE.-Reynolds (1869), Chem. Soc. J. 22, 1; Volhard (1874), Journ. prakt. Ch. (2) 9, 10; Claus (1875), An. Ch. Pharm. 179, 113. 50 grms. ammonium sulphocyanide. Fifty grms. dry ammonium sulphocyanide are melted (at about 160°) in a round-bottomed flask on the oilbath, and kept at a temperature at which the mass remains just liquid (140—145°) for 5-6 hours. The cooled melt is powdered and ground with two-thirds its weight of cold water, which dissolves unchanged ammonium sulphocyanide, and but little of the thiourea. By dissolving the residue, which has usually a somewhat reddish tint, in hot water, pure sulphourea is obtained on cooling in colourless crystals. Properties.-Colourless rhombic prisms (from dilute aqueous solution), long silky needles (from concentrated solutions), m. p. 175°. Very slightly soluble in cold water (one part thiourea dissolves in about eleven parts water at the ordinary temperature). LITERATURE.-Liebig, Wöhler (1838), Ann. Ch. Pharm. 26, 262. 10 grms. uric acid. hydrochloric acid (sp. gr. 1'19 diluted with an equal quantity of water). potassium chlorate. |