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are evolved; the reaction proceeds without the application of heat, and is complete when, on warming the liquid, nitrous fumes cease to come off. The product is now distilled; below 123° excess of nitric acid distils; between 123° and 194° a mixture of trichloracetic acid and a small quantity of nitric acid pass over, and at 194-196° nearly pure trichloracetic acid collects in the receiver and solidifies on cooling. The fraction boiling at 123-190° is treated with a fresh quantity of fuming nitric acid, and the product purified as above.

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LITERATURE. Frankland, Duppa; Fittig (1886), Grundr. der Org. Chem. 253.

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A mixture of 210 grms. oxalic acid dehydrated at 100° and 140 grms. absolute alcohol is slowly heated to 100° in a flask of about litre capacity connected with a condenser and receiver. The vapour of 140 grms. of a further quantity of absolute alcohol contained in a second flask is passed into the bottom of first flask, in a continuous, but not too rapid stream, the temperature of the contents of the latter being gradually raised to 125-130°. The liquid, which distils, consists of water, alcohol, and a small quantity of oxalic ether, and may be used for the preparation of oxamide. The latter on the addition of conc. aqueous ammonia is precipitated in the form of a white crystalline powder, C2 O2(NH2)2 The contents of the flask are now distilled, and the colourless liquid which passes over at 182—186° collected in a separate vessel,

C2H2O + 2C2H5OH
Oxalic Acid

=

C2O4(C2H5)2 + 2H2O
Diethyl Oxalate.

Properties.-Colourless liquid; b. p. 186°; sp. gr.

1103 at 0°; easily soluble in alcohol and ether; not miscible with water.

PREPARATION LXX.

ETHYL DIETHYL-OXYACETATE, CH1603

LITERATURE.

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Frankland, Duppa (1865), Proc. Roy.

Soc. 12, 396; 14, 17; Geuther, Wackenroder (1867), Zeitschcr. f. Ch. N. F. 3, 709; Fittig, Howe (1880), Ann. Ch. Pharm. 200, 21.

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litre

Fifty grms. oxalic ether are mixed with 107 grms. ethyl iodide in a round-bottomed flask of capacity, and so much granulated zinc (dried at 100°, and slightly amalgamated by dipping it into a weak. solution of corrosive sublimate) added, that it remains just covered by liquid. The mixture is heated. with reflux condenser on the water-bath for 1215 hours to 50-60°, when the liquid, which at the beginning is clear and of a light yellow colour solidifies to a yellowish-brown semi-crystalline mass. If water be now added to the product until its volume is three times that of the crystalline mass, a strong evolution of gas (ethane) occurs, and the ethyl ether separates out as an oil together with the

unattacked ethyl iodide and is distilled (in a copper vessel) with steam. The distillate is purified by fractional distillation. When the ethyl iodide and alcohol have distilled, the thermometer rises rapidly to 165°, and the portion passing over between 165° and 180° is collected separately. By repeatedly distilling this fraction the ethereal salt of diethyl oxalic acid is obtained pure.

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Properties. Colourless liquid; b. p. 175°: sp. gr. '9896 at 16.5°.

PREPARATION LXXI.

FORMIC ACID, CH2O2 = H.CO2H.

LITERATURE.-Berthelot (1856), Ann. Ch. Phys. (3) 46, 477; Lorin (1866), Bull. soc. chim. (2) 5, 7; (1870) (2) 14, 367.

150 grms. anhydrous glycerin.

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One hundred and fifty grms. commercial crystallised oxalic acid and 150 grms. glycerin dehydrated at

175° are heated in a retort of 2-litre capacity with condenser and receiver, on the water- or brine-bath. The reaction begins at 75°, and at 90° proceeds briskly; carbonic anhydride is evolved and aqueous formic acid distils. When the temperature has been maintained for some time at 90-105° and the evolution of carbonic anhydride has nearly ceased, the contents of the retort are cooled to about 80°, and a further 150 grms. crystallised oxalic acid added. The reaction recommences with the formation of aqueous formic acid, which, however, becomes more concentrated with each fresh addition of oxalic acid until the distillate contains 56 per cent. of the acid. In order to regain the formic acid, which remains as monoformin in the retort, the contents are diluted with about 1 litre water and distilled in a current of steam until the distillate has only a faintly acid reaction. On neutralising the united acid distillates by boiling with excess of lead carbonate and concentrating the filtered solution, the lead salt of formic acid is obtained in long colourless prisms, which decompose with sulphuretted hydrogen yielding the anhydrous acid. The powdered salt well dried at 100-110° is introduced in a long layer into the inner tube of a condenser loosely stopped at the lower end by a plug of glass wool, or asbestos.* To the end of the condenser a receiver is attached, which is guarded from moisture by a drying tube. The salt is heated

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