A N A L Y T I e A L CHEMISTRY Lecomte, J., Contrib. &de atructure mal., Vol. wmmdm. Victor Henri, 1947 148, 133. Lecomte, J., Gray, E., and Taboury, F. J.. Bull. soc. chim. France, 1947, 774. Lombard, R., Ibid., 1947,522. Luther, H., Er&Z u. Kohle, 2,179 (1949). Luther, H., and Lell, E., Angew. Chem., 61A,63 (1949). Maniere, B., and Barohewitz, P., Groupemat franc. devel. recherche8 C U ? T O ~ U ~ ~Note ., Tech. 56, (1946). Marignan, R., Bull. soc. chim. France, 1948,350. Zbid., p. 351. Masuno, M., Asahara, T., and Ishiguro, T., J. SOC.Chem. Ind. Japan, 49,192 (1946). Mathieu, J. P., J . phys. radium, 9,83(1948). Matossi, F.,and Mayer, R., Phya. Rm.,74,449(1948). Meister, A. G., J.Chem.Phye., 16,950 (1948). Menzies, A.C., and Skinner, J., J . phys. radium, 9,93 (1948). Moureu, H.,Sue, P., and Magat, M., Contrib. Pude structure mol., Vol. commhm. Victor Henri, 1947148,125. Mukerji, S. K., and Singh, L., Phil. Mag., 37,874 (1946). Pace, E.L., and Aston, J. G., J . Am. Chem. SOC.,70,566 (1948). Raman, C.V., Proc. Indian A d . Sci., 26A,339 (1947). Zbid., p. 356. Ibid., p. 370. Ibid., p. 383. Ibid., p. 391. Ibid., p. 396. Ramsay, D.A., Proc. Roy. Iyoc. (Lodon),A190, 662 (1947). Ramsav. D. A,. and Sutherland. G. B. B. M.. Ibid.. A190. 245 ‘ (1947). ’ Renard, M., Men. 8oc. my. aci. LUoe. 7,No. 1 (1945).
(82) Richards, C. M., and Nielsen, J. R., ANAL. CHEM.,21, 1036 (1949). (83) Robert, L.,Rev. inst. franG. pdtrole et Ann. combustibles liquidee. 3, 245 (1948). (84) Ryskina, S. I., J . Phys. Chem. (U.S.S.R.), 22,21 (1948). (85) Shemard, N.,J . Chem. Phus., 16,690 (1948). (86) Shorygin, P. P., J . Phys. Chem. (U.S.S.R.), 21,1125 (1947). (87) Smith, H. hI. J., Phil. Trans. Roy. SOC. (London), A241, 105 (1948). (88) Sushchinskii, M. M.,Bull. acad. sei. U.R.S.S., Skr. phya., 11, 341 (1947). (89) Szasz, G . J., McCartney, J. S., and Rank, D. H., J. Am. Chem. SOC.,69,3150 (1947). (90) Taboury, F. J., and Queuille, J., Bull. SOC. chim. France. 1947, 772. (91) Taboury, F. J., Thomassin, R., and Perrotin, Mlle., Ibid.. 1947, 783. (92) Theimer, O., Acta Phys. Austriaca, 1, 188 (1947). (93) Thompson, H.W., J . phys. radium, 9,172 (1948). (94) Treshchova, E. G., and Tatevskii, V. M., Doklady Akad. Nauk U.S.S.R., 61,841 (1948). (95) Tunnicliff, D. D., Rasmussen, R. S., and Morse, M. L., ANAL. CHEM., 21,895(1949). (96) Vassas-Dubuisson, C., J . phys. radium, 9,91 (1948). (97) Vassiliev, G.A.,Bull. SOC. chim. France, 1947,657. (98) Welsh, H.L., Crawford, M. F.,and Scott, G. D., J. Chem. Phys., 16, 97 (1948). (99) Wiemann, J., Bull. SOC. chim. France, 1947,479. (100) Wiemann, J., and Maitte, P., Ibid., 1947,764. (101) Zelinskii, N. D., Arbuzov, Yu. A., and Batuev, iM.I., Bull. acad. sci. U.R.S.S., Classe sei. chim., 1945,486. RECEIVED Uovrmber 14, 1919.
ULTRAVIOLET ABSORPTION SPECTROPHOTOMETRY E. J. ROSENBAUM, Sun Oil Company, Norwood, Pa.
D
URING 1949 few really new developments in the field of ultraviolet absorption spectrophotometry have come to the attention of this reviewer. There has been some progress, but this has been mostly in the direction of the refinement of existing methods and their extension to additional analytical problems. The absorption spectra of a number of compounds have been reported, usually in connection with molecular structure investigations. Of course, each spectrum is potentially the basis of a new analytical application. A rather detailed description of a method for determining individual Ce, C,, and C8 aromatic hydrocarbons in mixtures containing up to six of these components is given by Tunnicliff, Brattain, and Zumwalt (19). These authors include in their paper a considerable amount of useful basic information on calibration, test for and removal of interfering absorbers, etc. Vaughn and Stearn ($1) carry out the analysis of an isomeric rylene mixture in an unconventional way by making absorption measurements a t four wave lengths, calculating two pairs of differences between these measurements, and using these differences with a “working chart” set up during calibration to arrive at the desired analysis. The working chart is a ternary composition diagram based on absorption measurements on a series of mixtures of known composition made up from pure xylene samples. This method eliminates errors due t o background absorption which is independent of wave length and it is not limited in accuracy by deviations from Beer’s law because the calibration is based on mixture data. The analysis of mixtures of xylene isomers is also treated by Shostenko and Shtandel (15). The spectra of the four butylbenzenes and the three diethylbenxenes are reported by Stair (IC), who also discusses the analytical usefulness of the various absorption bands. The determination of total aromatics in gasoline is carried out h y Yzu and Doblas (W), using absorption in the range 260 t o 270 mp.
The problem of correcting for interfering absorption when it is impractical to remove all of the interfering material is treated by Tunnicliff, Rasmussen, and Xorse (20). By making use of spectrophotometric measurements a t a sufficient number of spectral positions, they algebraically obtain and correct for the interfering absorption. This method is reported t o give good results when applied t o the analysis of monocyclic aromatic hydrocarbons and of naphthalene in samples showing strong interference. The determination of naphthalene and the methylnaphthalene^ has received further attention. . 4 method is described by Armstrong, Grove, Hammick, and Thompson (1) who use a Hilger spectrograph and photographic photometry t o obtain their analytical data. A similar photographic method is applied by Bryant, Kennedy, and Tanner (S) t o the determination of naphthalene and its methyl derivatives in Trinidad petroleum Coggeshall and Glessner ( 4 ) describe a method of employing the Beckman spectrophotometer which they apply to hydrocarbon mixtures boiling in the kerosene range. An average error of 0.2% based on the total sample is reported for analyses of knonn mixtures. These authors present a simple empirical method for making a background correction in the determination of naphthalene A somewhat unusual application of ultraviolet spectrophotometry is the determination of biphenyl in orange peel hy S t e p and Rosselet (17‘). Murray ( 1 3 )determines total phenols in gasolines by extracting them with aqueous alkali and measuring ahsorption at 290 mg. LeRosen and Wiley (10) extract pyridine and related compounds from hydrocarbon mixtures by means of dilute phosphoric acid and determine their concentration by measurements at 255 mg. Benzaldehyde, present up to concentration of 0.1% as a contaminant in benzyl alcohol, is determined by Rees and Anderson ( 1 4 ) n h o dissolve the sample in a watermethanol mixture and measure absorption a t 283 mp. A method for determining acetaldehyde in monovinyl acetate a t concentra-
V O L U M E 2 2 , N O . 1, J A N U A R Y 1 9 5 0 tions of the order of O . O O l ~ ois given by Jullander and Brune (8). A micromethod for the determination of pentoses (0.5- t o 2-mg. samples) is presented by Dunstan and Gillam (6). They dehydrate the sugar with 85% phosphoric acid a t l'iO", steam-distill the resulting furfuraldehyde, and measure its absorption at 278.5 mp.
The ultraviolet absorption spectra of nicotine and related compounds have been intensively studied by Swain, Eisner, Woodward, and Brice (18). They point out the analytical applicability of their results. A rapid and precise method for caffeine is described by Ishler, Finucane, and Borker ( 7 ) . Two papers have appeared on the absorption spectra of steroid derivatives. In one, Mueller (12 ) describes the near-ultraviolet and visible spectra of steroid-antimony trichloride reaction products. I n the other, Djerassi and Ryan ( 5 ) report the spectra of steroidal dinitrophenylhydrazones. A method for the determination of penicillin G (bmzylpenicillin) which takes advantage of the characteristic absorption of the benzyl group is presented by Levy, Shaw, Parkinson, and Fergus (11). A background correction is made by measuring absorption a t a peak (264.5 mp) and a t an adjacent valley (263 mp) and using the difference for the analysis. The one instrumental development reported during the past year is the ultraviolet analyzer described by Kivenson, Osmar, and Jones (9). This is not a spectrophotometer but is actually a filter photometer. It is used for the continuous analysis of a Bowing styrene-butadiene sample. In a paper not directed specifically at ultraviolet methods-but parts of which are clearly applicable-Ayres ( 2 ) discusses the evaluation of accuracy in photometric analysis.
15 LITERATURE CITED
Armstrong, G. P., Grove, D. H., Hammick, D. L., and Thompson, H. W., J . Chem. SOC.,1948, 1700. Ayres, G. H., ANAL.CHEM.,21, 652 (1949). Bryant, D. C., Kennedy, G. T., and Tanner, E. M., J . Znat. Petroleum, 35, 508 (1949). Coggeshall, N. D., and Glessner, A. S.,ANAL.CHEM.,21, 550 (1949).
Djerassi, C., and Ryan, E., J . A m . Chem. SOC.,71, 1000 (1949). Dunstan, S., and Gillam, A. E., J . Chem. SOC.,1949, S 140 (supplementary issue). Ishler, N. H., Finucane, T. P., and Borker, E., ANAL.CHEM.,20, 1162 (1948).
Jullander, I., and Brune, K,, Acta Chem. Scand.. 2, 204 (1948). Kivenson, G., Osmar, J. J., and Jones, E. W., ANAL.CHEM.,21, 769 (1949).
LeRosen, H. D., and Wiley, J. T., Zbid., 21, 1175 (1949). Levy, G. B., Shaw, D., Parkinson, E. S.,and Fergus, D., Ibid., 20, 1159 (1948).
Mueller, A,, J . Am. Chem. Soc., 71, 924 (1949). Murray, M. J., ANAL.CHEM.,21, 941 (1949). Rees, H. L., and Anderson, D. H., Zbid., 21, 989 (1949). Shostenko, Y .V., and Shtandel, A. E., Zhur. Priklad. Khim., 21,. 408 (1948).
Stair, R., J . Research Natl. Bur. Standards, 42, 587 (1949). Steyn, A. P., and Rosselet, F., Anal&, 74, 89 (1949). Swain, M. L., Eisner, A., Woodward, C. F., and Brice, B. A., J . Am. Chem. SOC.,71, 1341 (1949). Tunnicliff, D. D., Brattain, R. R. and Zumwalt, L. R., ANAL. CHEM.,21, 890 (1949). Tunnicliff, D. D., Rasmussen, R. S., and Morse, M. L., Ibid., 21, 895 (1949).
Vaughn, R. T., and Stearn, A. E., Ibid., 21, 1361 (1949). Yzu. L.. and Doblas, J.. Inat. nacl. thc. aerondut ( M a d d ) , Commun., No. 7 (1945). RBCEIVED December 1, 1949
X-RAY ABSORPTION HERMAN A. LIEBH.iFSKY, General Electric Company, Schenectady, N . Y .
T
H E present review continues the classification and order laid down in 1948 ( 7 ) ,but it is less theoretical and introduces x-ray fluorescence and safety as new topics. Progress during 1949 in the use of analytical methods based upon x-ray absorption has been steady and greater than the published literature taken alone would indicate. X-RAY ABSORPTION SPECTROMETRY
Work on the Dow automatic x-ray absorption spectrometer continued during 1949 (3). X-ray tube space current and excitation potential have been stabilized until the statistical fluctuation in the low intensity x-rays is the only evident source of error. The ratemeter circuit for recording the Geiger tube output was improved by incorporating certain recent developments in electrical circuits. Analyses by the method of Glocker and Frohnmayer (see 7 , Figure 3 ) have been carried out for nickel, zinc, selenium, bromine, rubidium, strontium, and mercury. Routine determinations of hydrogen, carbon, nitrogen, oxygen, silicon, sulfur, and chlorine in simple compounds have been made by measuring the absorption of monochromatic x-rays in regions of continuous absorption. X-RAY ABSORPTIOMETRY WITH POLYCHROMATIC BEAMS
With x-rays, as with radiant energy of longer wave lengths, it is generally true that the precision of an absorptiometric method is significantly increased by making the method comparativei.e., by commuting in the x-ray beam between the unknown and a suitable standard, such commutation preferably being rapid. This fact was applied in the three recent investigations discussed chronologically herewith.
Kehl and Hart (6) adapted the North American Philips (Geiger counter) x-ray spectrometer to the quantitative determination of sulfur in hydrocarbons. The sample, contained in a glass cell, was placed in the direct beam from an iron-target tube. Six readings were made in each determination, taken alternately on standard and unknown. Variations in the absorption of the hydrocarbon base stock were compensated by use of a calibration curve that correlated transmitted intensity and specific gravity. By the method developed, a technician could obtain in 10 minutes, and to within *0.025%, the sulfur content of a sample containing from 0 to approximately 3% by weight of that element. The comparative method has been applied satisfactorily on a laboratory photometer (19) to the identification of pure compounds, the determination of tetraethyllead fluid in gasolines, and the determination of sulfur in crude oils. The determinations of tetraethyllead fluid were carried out on gasolines supplied as unknowns by the Ethyl Corporation. The x-ray results could be expressed in equations such as Equivalent thickness (cm. of Al) = 0.3815 Equivalent thickness (cm. of AI) = 0.3830
+ 0.0370s + 0.046%
(1)
(2)
I n these equations, which are of the slope-intercept type, the intercept represents the absorption of the base stock, and the amount of tetraethyllead present is established by the slope. The precision attained was generally comparable with that (estimated to be *0.02 ml. per gallon) of the chemical method for tetraethyllead fluid. As Equations 1 and 2 indicate, the precision was sufficiently great to warrant consideration of the difference in the base-stock gasolines. Another of the deviations that can occur with polychromatic
