Structure of Stearic Acid Films on Copper

Abstract

IN a recent communication¹, Spink, using electron diffraction technique, postulates the presence of copper stearate after a copper surface covered with stearic acid has been heated. Two facts are quoted in support of this hypothesis. (1) When such a film is heated in the diffraction camera, the pattern finally fades at a temperature of 127–130° C., that is, close to the softening point of copper stearate. This observation confirms that of Brummage², and also corresponds well with friction measurements reported by Gregory and Spink³. It is generally accepted that both the electron diffraction and the friction evidence are circumstantial and do not offer a direct proof of the presence of the soap. (2) After the acid-covered surface has been heated, the film may be removed in benzene and then deposited on collodion. The resulting film gives an excellent diffraction pattern which is identical with that of copper stearate prepared in the laboratory.