V O L U M E 21, NO. 12, D E C E M B E R 1 9 4 9
1511
planned to study the direct weighing method further in an effort t o determine t,ht, factors which militate against its m e in alloy and ore samples. .ACTION WITH ALKALI
Iiurniiib fouiii! that zirconium mandelate dissolves in sodium hydroxide with the production of zirconyl hydroxide, and in ammonium hydroxide without the production of a precipitate. T h e halomandelittes show this same action. Feigl ( 2 ) has pointed out the unusual nature of the reaction of ammonia with zirconium mandelate. This interesting masking action will be studied further from the standpoint both of possible analytical applications a n d of the isolation of a npn‘ clas‘: of inner-complex compounds. ACKSOU LEDGhlEYT
T h e authors wish t o thank the Titanium Alluy Division of t,he Xational Lead Company for furnishing thc zii,conium samples used in this rwearc1-i.
LITERATURE CITED
(1) Collet, Bull. soc. chim.,131 21,65 (1899). (2) Feigl. Fritz, “Chemistry of Specific, Sensitive, and Selective Reactions,” Kew York, Academic Press, 1949. (3) Fosdick and Wessinger, J . Am. Chem. SOC., 60, 1465 (1938). (4) Heller, Ber., 37,948 (1904). (5) Ihid., 46, 280 (1913). (6) Ibid., p. 3976.
(7) Hillebrand and Lundell, “Applied Inorganic Analysis,” New York, John K l e y 8: Sons, 1929. (8) Holm, Sagel, Reichl, and Vaughan, Technical Industrial Intelligence Division, U. S. Dept. Commerce, FIAT Final R e p t . 1000. (9) Klingenberg, J . J., dissertation, Ynirersity of (’incinnati, 1949. (10) Kumins, - ~ A L CHEM., . 19, 376 (1947). (11) Organic Synthesis, Coll. Vol. 1, p. 8 9 (1941). (12) .%hu.eiteer, Ber., 24, 547, 997 (1891). I~ECEIVE Maj D 2 3 1949. Abstracted from a dissertation submitted t o the Graduate School, University of Cincinnati, in partial fnlfillment of the reiliiirenient-; of t h e drgree of Ph.D., 1949.
Self-Absorption Curves of C’‘=-Labeled Barium Carbonate, Glucose, and Fatty Acids Influence of Physical Form of Sample A K 3 E S. WICK, H i R R Y N. BARNET, AhD NANCY ACKEKRIAS Scripps Metabolic Clinic, La Jolla, Calif.
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Comparative s e If P bsor p t i o n curves of C’d-labeled barium carbonate, glucose, and fatty acids are given. It is shown that these curves are dependent on the technique employed in the sample preparation. In counting solid samples the physical form and density should be comparable in order to obtain reproducible results.
4
I 0.4
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15 PO MG. PER SO. C M .
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35
40
OF SAMPLE Figure 1. Relative Absorption Curves for Dry- and Wet-Ground BaCI403 1.
Barium carhonatc, dry ground.
2.
Barium carbonate, wet ground
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ELF-absorption is of considerable importance in the measurement of C i 4 in solid samples. I n biological experiments where only relative activity is desired and if sufficient material is available, it i 3 possible to minimize the self-absorption factor by counting a sample of material so thick that the radiation emitted from the bottom layer of the sample cannot penetrate to the
ANALYTICAL CHEMISTRY
1512
counter. It has been frequently stated that the only requirement for the measurement of thick samples is that the material be well mixed and the top of the precipitate be flat and smooth. When an insufficient amount of material is available for the socalled "saturation thickness" measurement, a calibration curve is used for obtaining comparative results by calculating to infinite thickness, zero thickness, or a reference density. Absorption curves for BaC1403have been reported b j Libbl ( 3 ) and others (1, 4, 6). Except for the work of Yankwich and Weigl ( 7 ) , who compared the relationship of back-scattering to selfabsorption of samples of BaCI4O3 and C1a-labeled p-phenylphenacyl acetate dissolved in \ v a ~and mounted on aluminum, data are lacking for other substances. Direct counting of various compounds iq often desirabl~in dealing v i t h low count samples. In this report the importance of technique in the preparation of samples using C14--labeledbarium carbonate, glucose, and fatty acids is shown. The glucose was obtained by plant leaf synthesis and the fatty acids were isolated from rats that had received radioactive glucose. The counting IT as carried out with a mica end windon- counter (Tracerlab T G C-2) of 1.86 mg. per sq. cm. The sample mounts were made from 0.032-inch gage sheet aluminum. The counting area, 3.78 sq. cm. in a 0.3-mm. depression, was 3 mm. from the counter window. The C1%beled barium rarhonate, glucose, and fatty acid samples gave 5000, 5000, and 1000 total counts per minute, respectively, a t infinite thickness. hpproximately 20 planchets were used for the fatty acid calibration cuive For each of the barium carbonate and glucose curve? approumntely 50 samples of diff erent densities were prepared The data obtained with these samples are shonn in Figures 1 and 2, in nhich the fiaction of maximum activit) and the fraction of maximum qppcifir activit\- RI'P plnttrd against sample thickness The technique used in prepamg the samples from which BaCI4Os ( S o . 2, wet ground) and radioglucosr ( S o . 2, crystalline) were obtained is the same as that employed by Dauhen, Reid, and Yankwich ( 2 ) . The carbonate (or glucose) \\-as ground in an agate mortar under 95% ethanol. After a few minutes' grinding, the slurry formed was allowed to stand for a f a 7 seconds to permit the coarse particles to settle out and the suspension of fine particles was added to the planchets. The sninples were dried under an infrared lamp. The result for the BaC1403curve (Figure 1)prepared under these conditions is essentially that reported by Yankwich ( 6 ) and A4rnistrong ( I ) . The nbsoiption curve for radioglucose prepared under identical conditionq gave a somewhat similar curve, although the point of "saturation thickness" was attained at a slightly greater density. Of particular interest mere the results obtained by preparing the radioglucose and carbonate planchet5 under different conditions. Glucose curve 1 (amorphous) nab obtained by dissolving the radioglucose in water and drying in an oven a t low temperature folloived by a 1-week drying time in a desiccator over fresh Drierite. This procedure, which gave amorphous glucose samples with a glossy finish, had the effect of a general lowering of the entire curve and a shifting of the point of infinite thickness from 20
c
to 25 mg. per sq. cm. The BaC1403curve 1 (dry ground and sanw material as used in 2) was made by grinding the dry powder in air agate mortar and placing the ground material on the planchets. Ethanol (95%) was added to make a slurry of the coarse and fine particles which was spread out uniformly with a stirring rod. After settling, the material was dried with the infrared lamp a,before. The samples prepared by this method appeared uniforni and similar to those made for curve 2, although a trained observer could detect a difference in the smoothness of the samples prepared by the two techniques. I t is seen in Figure 1 that this procedure gave an absorption curve of considerable variance from curve 2 with the point of infinite t'hirkness a t approximately 35 mg. per sq. cm. The above determinations for BaC"O3 were repeated usiug copper planchets of the same design. The self-absorption curves resulting from the two methods of sample preparatiou were, for all practical purposes, the same as those obtained wit 11 the aluminum background. The solid C14--labeledfatty acids were spread on the planchet? arid softened with an infrared lamp to give a smooth top surface upon cooling. Under the same condition of counting, the fatt! acid samples gave a curve similar to the wet-ground BaC1403. The most reasonable explanation of the variable results obtained with the CI4-labeled barium carbonate and glucose samples prepared under different conditions of preparation is the effect of packing due to physical form and density of the solid substance This appears to be especially pertinent, because the self-absorption curves of C14 radiation are functions, among other thing,.. of the scattering and absorbing powers of the sample. Extremca care must be exercised in obtaining uniform sample preparatiori. not only when dealing with the thin samples but also when dealing with samples in the range of infinite thickness. I n view of the fact that two distinctly different, correction curves can be obtained for either C1a-labeled barium carbonatr or glucose by an alteration of the sample preparation technique) it is not surprising that some of the points in Figurtv
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OF SAMPLE
Relative Absorption Curves for Cld-Labeled Glucose (Amorphous). Glucose (Crj stalline), and Fatty Acids
Figure 2. 1.
Glucose, amorphous.
2.
Glucose, crystalline.
3.
Fatt: acids
V O L U M E 21, NO. 12, D E C E M B E R 1 9 4 9
1513
1 and 2 deviate considerably from the designated curve. T h a t this deviation of individual samples from the curve is a characteristic of the sample and not due to counting error was established by recounting, which always gave the same results. LITERATURE CITED I
1)
wig, K-. I)., (1948).
Ai n i b t i
and Schubert, Jack, ANAL.CHEY.,20, 270
(2) Dauben, 11'. G., Reid, J. C., and Yankwicli, P. E., Ibid., 19, 828 (1 9 4 7 ) .
W.F., I b i d . , 19, 2 (1947). Reid, A. F., Weil, A . S., and Dunning, J. R., I b i d . , 19, 824 ( 1 9 4 7 ) . Yankwich, P. E., Piorris, T. H., and Huston, John, Ibid., 19, 439
(3) Libby, (4) (5)
(1947).
(6) Tankwich, P. E., Rollefson, G. K., and Norris, T. H., J . C'hern. Phys., 14, 131 ( 1 9 4 6 ) . (7) Yankivich, P. E., and Weigl, J. W., Science, 107, 651 ( 1 9 4 8 ) . RECEIVED April 25, 1940. Investigation supported by a research grant from the Division of Research Grants and Fellowships, National Institutes of Hralth, IT. S. Puhlir Health Servire.
Determination of Aluminum Nitride Nitrogen in Steel H. F. BEEGHLY Jones untl Laughlin Steel Corporation, Pittsburgh, Pa.
4 method for determining aluminum nitride nitrogen in steel utilizes solutions of the halogens in an anhJdrous aliphatic ester to dissol\e the iron matrix without decomposing the aluminum nitride in the steel. The residue containing the aluminum nitride is recovered from the ester-halogen solution and reaction products by filtration. The nitrogen content of the recovered aluminum nitride is obtained by the method for determining nitrogen in steel described by the author in an earlier paper. The ester-halogen method requires inexpensit e
N
ITROGEX and its compounds exercise a significant influence on the properties of steel and on its response to thermal rreatinent. Development of analytical methods which enable the total amount of nitrogen or the amount of a given nitrogen compound to be determined ~ i t ah minimum of time and labor is a prerequisite to most efficient resrarch upon the iiifluence of nitlogen in steel. Much intrrest in austenitic grain size of steel n a s aioused n hen .\Ic&uaitl and Ekin ( 2 7 ) published an account of their woik on the relation of grain size and heat treatment in 1922. Since then, the use of aluminurn in steel making for modifying such characteristics as grain size, strain sensitivitl-, and aging has become an accepted conimeicial practice. The role of aluminum in controlling these charscteristics has been investigated extensively ( 2 , 4-17. 19-2.5, SO, 31) and it has been postulated that they are governed by the presence of flee aluminum, aluminum oxide, :ind aluminum nitride. Considerable indirect evidence has heen ,recumulated regarding rach of these hypotheses, but direct experimental data arc meager (18). Recent investigations support the premise that aluminum nitride is perhaps the most impoitant tnctor in controlling the properties of aluminum-killed steel. Despite the well recognized need for a method of determining this compound quantitatively, a satisfactory procedure has heen lacking. The fractional vacuum fusion method, investigated for this purpose, involves the assumptions that only aluminum nitride nitrogen nil1 be liberated in the high temperature fractions and that the steel ill lose none of its aluminum nitride nitrogen a t Ion er temperatures. Results so obtained may be misleading. The writer has described a simple, economical method for determining combined nitrogen in steel ( 3 ) . The present paper describes convenient methods and reagents for determining its aluminum nitride nitrogen content quantitatively. The aluminum nitride is separated from the steel matrix and its nitrogen rontrnt is determined by the usual procedure involving steam
apparatus, is simple to use, and > ields highly reproducible results. It is not subject to interference from compounds of the elements commonly used in steel. The procedure is economical enough for routine use and sufficiently accurate and precise for research investigations. I t has been used successfully for a large number of analj ses in establishing the changes in the aluminum nitride content of steel caused by different thermal treatments and fabricating operations and in inrestigating deoxidation and steelmaking processes.
distillation in micro-Kjeldahl apparatus and the Sessler coloi reaction. The reagents used for separating aluminumnitride from steel are solutions of halogens in anhydrous aliphatic esters of organic acids; bromine dissolved in methyl acetate has been used most extensively. The ester-halogen method is useful for separating certain of the nonmetallic compounds such as aluminum nitride from steel in a form that enables them to be analyzed b y microchemical or spectroscopic methods and identified by x-ray diffraction techniques. The reagents and procedure are suitable both for research on the behavior of nonmetallic compounds in steel and for quantitative routine control analyses. Considerable research in chemical metallurgy and steelmaking \vas necessary in securing material to establish the validity of the ester-halogen method for the determination of aluminum nitride in carbon steel. -1detailed description of the work is not n-ithin the scope of this paper. Limited amounts of the data so obtained have been published (32) and those secured in other phases of the investigation will be presentrd in paprrs now in process of pub1ic:ttion. REAGENTS
The reagents required for the extraction of aluminum nitride from steel are bromine and methyl acetate of analytical grade. Those necessary for determining the nitrogen content of the alumirium nitride are given in an earlier paper ( 3 ) . APPARATUS
Aluminum nitride is most conveniently separated from stwl with reflux extraction units such as are illustrated in Figu,e 1. They consist of 200-ml. beakers connected to indented IVcsttype condensers by means of 55/35 standard-taper joints. -4 drying tube may be attached t o the t80p of the condenser by
