ANALYTICAL CHEMISTRY
lQ4 The determination of molecular weights with less accuracy is much simpler (5, 17, 25). ACKNOWLEDGMENT
The author is grateful to C. B. Gill for correcting the English of the manuscript. LITERATURE CITED
(1) Andrews, K.W.,Minepalog. Mag., 29, 85 (1950). (2) Batuecas, T.,Nature, 165, 61 (1950). (3) Birge, R. T.,Am. J . Phys., 13, 67 (1945). (4) Buerger, M. G., “X-Ray Crystallography,” p. 395,New York, John Wiley & Sons, 1942. (5) Bunn, C. W.,“Chemical Crystallography,” p. 185, Oxford, Clarendon Press, 1946. (F) Clark, G. L., “Applied X-Rays,” 3rd ed., pp. 267,291,305,309, Xew York, McGraw-Hill Book Co., 1940. (7) Cohen, M.U.,2. Krist., 94A,288 (1936). (8) DuMond, J. W. M., and Cohen, E. R., Am. Scientist, 40, 447, 458 (1952). (9) Feigl, F., “Chemistry of Specific, Selective, and Sensitive Reactiona,” p. 161, New York, Academic Press, 1949. (IO) Hutchison, C. A., J. Chem. Phys., 10, 489 (1942). (11) Hutchison, C. A., and Johnston, H. L., J . Am. Chem. Soc., 62, 3165 (1940); 63, 1580 (1941). (12) Hutchison, D. A., J . Chem. Phys., 13,383 (1945). (13) IevinB, A., and Straumanis, M., 2. K~ist.,94 A, 40,48 (1936). (14) Ievins, A., and Straumanis, M., 2. Physik., 116, 194 (1940). (15) Jette, E.R.,and Foote, R., J . Chem. Phys., 3, 605 (1945). (16) Johnston, H. L.,and Hutchison, D. A,, Phys. Rev., 62,32 (1942). (17) Senti, F. R.,and U’arner, R. C., J . Am. Chem. Soe., 70, 3318 (1948).
(18)Siegbahn, M.,“Spektroskopie der Rontgenstrahlen,” 2nd ed., p. 43,Berlin, Julius Springer, 1931. (19) Stahl, W.,and Straumanis, M., 2. physik. Chem., 193, 121 (1944). (20)Straumanis, M. E.,Acta Cryst., 2, 82 (1949). (21) Straumanis, hl. E.,Am. Mineral., in press. (22) Straumanis, M. E.,J. Am. Chem. SOC.,71, 679,681 (1949). (23) Straumanis, M. E.,J . Appl. Phys., 20, 726 (1949). (24) Straumanis, hf., 2. anorg. Chem., 233,201 (1937). (25) Straumanis, M. E.,2. Physik, 126, 49 (1949). (26)Ibid., p. 65. (27) Straumanis, hf. E.,and Aka, E. Z., J. Am. Chem. Soc., 73,5643 (1951). (28) Straumanis, hf. E., and Aka, E. Z., J. Appl. Phys., 23, 330 (1952). (29) Straumanis, M. E.,and Aka, E. Z., Rev. Sci. Instr., 22, 843 (1951). (30) Straumanis, M. E., and Dravnieks, A,, 2. anal. Chem., 120,168 (1940). (31) Straumanis, M.,and Ence, E., 2. anorg. Chem., 228, 334 (1936). (32) Straumanis, M. and Ievini, A., “Die Prazisionsbestimmung
von Gitterkonstanten nach der asymmetrischen Methode,” Berlin, Julius Springer, 1940; Ann Arbor, hfich., Edwards Brothers, Inc., 1948. (33) Straumanis, M. E.,and Stahl, W., 2. physik. Chem., 193, 97 (1943);2. anal. Chem., 128,60 (1947). (34) Straumanis, M. E.,and Stahl, W., 2. physik. Chem., 194, 129 (1944). (35) Walden, G. H., Jr., and Cohen, M. U., J. Am. Chem. Soc., 57, 2591 (1935). (36) Wichers, E., Zbid., 74,2447 (1932). RECEIVED for review November 19, 1952. Accepted March 3, 1953.
Quantitative Analysis of Powder Mixtures with the Geiger-Counter Spectrometer HAROLD P. KLUG Department of Research in Chemical Physics, Mellon Institute, Pittsburgh 13, Pa.
The advent of the Geiger-counter spectrometer in 1945 introduced new possibilities for precise quantitative analysis of powder mixtures, by providing intensity measurements of superior accuracy. Almost immediately thereafter, because of the wide interest in quartz determination in industrial dusts, the whole problem of precise quantitative analysis with the spectrometer came under investigation. These studies have demonstrated that the reproducibility attained in the intensity measurements is dependent upon the attention given to such factors as instrument stability, crystallite size of the powder, mount-
A
S EARLY as 1919 Hull (9) pointed out the simplicity and
advantages of the powder diffraction method for chemical analysis. It was not until 1936, however, that the first significant application in quantitative analysis was published, Clark and Reynolds’ technique (6) for quartz determination in mine dusts. This pioneering contribution gave a great impetus to quantitative x-ray analysis, and it has since been the basis for nearly all work in powder analysis. The experimentally more simple qualitative identification by means of powder patterns was not put on a routine basis until the well-known work of Hanawalt, Rinn, and Frevel (8) appeared two years later. These two studies are, indeed, almost wholly responsible for the important position x-ray diffraction occupies in the modern analytical laboratory. The advent of the Geiger-counter x-ray spectrometer ( 7 ) in 1945 introduced new possibilities for precise quantitative analysis.
ing of the specimen, and type of scanning technique. The absorptive properties of the sample and the number of components present determine the analytical procedure to be used. Results in the general case, which requires an internal standard, are illustrated by data on the determination of quartz in industrial dusts using calcium fluoride as a standard. Single determinationg by manual counting with recent model spectrometers usually yield the quartz content within 5 % of the actual amount present in the range 5 to 100% quartz. Below 5% quartz the error may be two or three times as great.
It provided excellent angular accuracy and resolution for the identification procedures, and it made possible intensity measurements of high accuracy without the uncertainties arising from film graininess, the microphotometering technique, and the intensity-blackening relationships for x-ray film (4, 5 ) . This laboratory, because of its interest in the determination of quartz in industrial dusts, was among the first to investigate the whole problem of precise quantitative analysis with the spectrometer (1-8, 10,11). PRECISION AND REPRODUCIBILITY
It was soon evident that the degree of precision and reproducibility attained in the intensity measurements is dependent upon the attention given to a number of factors: (I) instrument sta-
V O L U M E 25, NO. 5, M A Y 1 9 5 3
705
Table I. Typical Stability and Reproducibility Studies with a Recent Model of Spectrometer Study NO.
1
2
3
4
Nature of Sample and Specimen Pure quartz powder,
