“…Earlier work on porphyrins utilized optical measurements on crystals under the microscope for identification purposes (4, 12, 14) and also goniometric determination of interfacial angles (31). Later, powder patterns were taken to help prove identity between preparations obtained by different routes (2,5,6,23,30,32,34). No d-spacings and intensities were reported except for nine porphyrin esters (19, S3) and Cu etioporphyrin II (18); only one pattern, that of hemin, can be found in the 1958 Index of the A. S. T. M. Powder Data File.…”