A novel crystalline adduct of diphenyl oxalate and phenol in a molar ratio of 1:2 and having a high purity is produced by melting a mixture containing diphenyl oxalate and phenol at a temperature of 100°C or more; cooling the melt to a temperature of less than 100°C to allow a resultant adduct of diphenyl oxalate and phenol in a molar ratio of 1:2 to crystallize and deposit from the melt; and collecting the crystalline adduct, and is utilized to produce diphenyl oxalate with a high purity by melting the crystalline adduct to dissociate it into diphenyl oxalate and phenol, and evaporating away the dissociated phenol from the melt to collect the dissociated diphenyl oxalate.
                            草酸二苯酯和
苯酚的摩尔比为 1:2 且纯度很高的新型结晶加合物是通过以下方法制得的:在 100°C 或更高的温度下熔化含有
草酸二苯酯和
苯酚的混合物;将熔体冷却到低于 100°C 的温度,使摩尔比为 1:2 的
草酸二苯酯和
苯酚的加合物结晶并从熔体中沉积下来;收集结晶加合物,并通过熔化结晶加合物使其解离成
草酸二苯酯,从而制得纯度很高的
草酸二苯酯: 将结晶加合物熔化,使其离解为
草酸二苯酯和
苯酚,并从熔体中蒸发掉离解的
苯酚,收集离解的
草酸二苯酯,从而生产出高纯度的
草酸二苯酯。