cision and accuracy with which a num ber of crystallographic constants can be determined. In the case of Procaine Penicillin G, for example, the beta angle can vary from 90° to about 150° and the accuracy of measurement is about ± 2 ° . There is, therefore, the possibility of discriminating between about 900 different compounds ( 150-90 times 60/4) by means of the beta angle alone. Furthermore, there are listed 34 x-ray powder diffraction lines with correspond ing intensity values for this same com pound, each measurable to ±0.01 or better with a degree of discrimination of 1 in 1000. Now, compare the accuracy of these measurements with that of measuring melting points, ± 1 - 2 ° C. (if you're honest) and a degree of discrimination of. at best, 1 in 100. Finally, consider the possibility of finding any two com pounds with an identical set of the above crystal constants, one chance in about 10". and this without considering x-ray powder data. N o other set of physical measurements (e.g., infrared absorption, mass spectrometry, or nuclear magnetic resonance) is as distinctive or as gen erally applicable in identification of a chemical compound. The usefulness of crystal data in anal ysis, unfortunately, depends on the avail ability of such data, and in a useful form. Sources such as Winchell(4, 5), Donnay and N o w a c k i ( / ) , Larsen and Berman(2), and Porter and Spiller (3) are standard in this field. I n a small way, we have tried to encourage the determination of crystal data for analytical use. With the active assistance and support of ANALYTICAL CHEMISTRY we have been able to increase the number of published descriptions dur ing the past 10 years by about 230 with about 8 0 % of these complete with re spect to both x-ray and refractive index data. March 1959 was the beginning of the twelfth year for this regular publica tion of crystal data in ANALYTICAL CHEMISTRY. T h e object of this paper is to recapitulate and tabulate the data published during the past 11 years in useful analytical form. At the same time we might add that we encourage the submission of additional data for pub lication in this way. LITERATURE CITED
1. Donnay, I. D . H., and Nowacki, W., "Crystal Data," Geological Society of America, 1954. 2. Larsen, H., and Berman, "Microscopic Determination of the Non-Opaque Minerals," TJ. S. Geol. Survey Bull. 848 (1934). 3. Porter, M. W., and Spiller, R. C., "The Baker Index of Crystals," W. Heffner & Sons Cambridge, England, vo.. I, 1951. 4. Winchell, A. N., "Microscopic Char acter of Artificial Minerals," John Wiley & Sons, Inc., New York, 1931. 5. Winchell, A. N., "Optical Properties of Organie Compounds," Academic Press, 1954.
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VOL. 3 1 , NO. 7, JULY 1959
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