The isoxazolone was described as a substance capable of existing in two modifications-the ordinary form first mentioned by Beckmann and Paul, and an unstable, lower-melting, more acidic form which immediately yielded a copper derivative when its ethereal solution was shaken with aqueous copper acetate. This conclusion led to the present investigation. If correct, it would mean that diphenyl isoxazolone is the only isoxazolone derivative- ...