CHEMICAL COMPOSITIONS FOR COMMERCIAL, SCIENTIFIC AND PHOTOGRAPHIC PURPOSES-NAMELY, EVAPORATION CHEMICALS, THE LATTER BEING SOLID COMPOUNDS CAPABLE OF VAPORIZATION UNDER VACUUM WITHOUT DECOMPOSITION AND BEING DEPOSITABLE ON A SURFACE AS A THIN FILM FOR SPECIAL OPTICAL, MECHANICAL OR ELECTRICAL PROPERTIES, SAID EVAPORATION CHEMICALS INCLUDING, E.G., PARTICLES OF HALIDES, SULFIDES, SELENIDES OR OXIDES