PREPARATIONS 119 ammonia solution is employed chiefly to prevent too great a rise in temperature during the reaction.) Now add i ml. (i-i g.)of ethyl oxalate, cork the flask securely and shake vigorously: the mixture becomes perceptibly warm, and therefore throughout the shaking hold the cork tightly in position, with the flask pointing away from the operator (and from neighbouring students!). At intervals, release the pressure by cautiously removing the cork. The oxamide rapidly separ-ates as a white powder and after 15 minutes' shaking the reaction is complete. Filter off the oxamide at the pump, wash it well with water and drain thoroughly. Dry by pressing between sheets of drying-paper, or in a desiccator. Yield 0-5 g. The low solubility of oxamide in most liquids makes recrystallisation very difficult: the product obtained in this preparation when dried is pure, however, and recrystal-lisation is therefore not necessary. Oxamide has no definite melting-point, as on heating it partly sublime* and partly decomposes. Succinamide. NH
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