“…While the determination of a cooling curve is considered the best method of establishing the purity of a solid organic compound, it is seldom used because it requires several grams of the sample. The recent publication of a method (316) using only 200 to 300 mg. should make this excellent procedure of more general application. The material contained in a special glass tube is placed in a copper block and heated so that a constant difference in temperature is maintained between the sample and its surroundings.…”