INDUSTRIAL AND ENGINEERING CHEMISTRY Quastel, J. H., and m7heatley, A. H. M., Biochem. J., 28, 1521 (1934).
Roberts, E. A. H., Ibid., 35, 909 (1941). Roughton, F. J. W., J. BWZ. Chem., 141, 129 (1941). Ibid., 137,617 (1941). Samisch, R., Ibid., 110,643 (1935). Schlayer, C., Biochem. Z.,297, 395 (1938). Schmitt, F. O., Am. J . Physiol., 104, 303 (1933). Schultz, A. S.. Atkin. L.. and Freu, C. N., IND.ENG.CHEM.. ANAL.ED..14. 35 (1942). Schultz, A. S . , Atkin, L.; and Frey, C. N., J . Am. Chem. Soc., 59,2457 (1937). Ibid., 60, 3084 (1938). Ibid., 62, 2271 (1940). Schults, A. S.. Atkin, L., and Freu. C . N., J . Bid. Chem.. 136, 713 (1940). Schults, A. S., and Landis, Q., J. Am. Chem. SOC.,54, 211 (1932). Singh, B. N., and Mathur, P. B., Biochem. J., 30, 323 (1936). Sizer, I. W., J . Biol. Chem., 132, 209 (1940). Sizer, I. W., and Tytell, A. A., Ibid., 138, 631 (1941). Smith, F. B., and Brown, P. E., Iowa Agr. Exptl. Sta. Res. Bull. 147,27 (1932). Specht, H., J . Cellular Comp. Physiol., 5, 319 (1934). Stadie, W. C., Luckens, F. D. W., and Zapp, J. A, Jr., J . Bid. Chem., 132, 393 (1940). Stefanelli, A,, J . Ezptl. Biol., 14, 171 (1937). Summerson, W. H., J . B i d . Chem., 131, 579 (1939). Taylor, D. L., Science, 95, 129 (1942).
Vol. 15, No. I
(85) Thomas, J. O., and DeEds, F., Ibid., 86, 107 (1937). (86) Thimann, K. V., and Commoner, B., J . Gen. Physiol., 23,333 (1940). (87) Thunberg, T., Zentr. Physiol. 19, 308 (1905). (88) Tobias, J., and Gerard, R. W., Proc. SOC.Eaptl. Bid. Med., 47, 531 (1941). (89) Van Slyke, D. D., and Neill, J. M., J . Bid. Chem., 61,523 (1924). (90) Victor, J., Brit. J. Ezptl. Path., 16, 233 (1935). (91) Warburg, E., Sitzberg. preuss. A k a d . Wiss., 34, 712 (1900). (92) Warburg, O., Biochem. Z., 152, 51 (1924). (93) Ibid., 142,317 (1923). (94) Warburg, O., “Uber die katalytischen Wirkungen derlebendigen Substanz”, Berlin, Julius Springer, 1925. (95) Warburg, O., “Uber den Stoffwechsel der Tumoren”, Berlin, Julius Springer, 1926; tr. by F. Dickens, London, Constable & Co., 1930. (96) Warren, C. O., Science, 94, 97-8 (1941). (97) Weil, L., and Russell, M. A,, J. Bid. Chem., 106, 505 (1934). (98) Widmark, E. M. P., Skand. Arch. Arch. Physiol., 24,321 (1911). (99) Winterstein, H., 2. allgem. Physiol., 6 , 315 (1907). (100) Woodward. G. E.. J. Biol. Chem.. 109. 1 (1935). (101) Wooldridge, W.R., and Standfast, A’. F: B., Biochem. J.,30, 141,149-62 (1936). I . , J . Pharmucol., 71, 164 (1941). (102) Wright,
c.
P R E S ~ N T before ED the Divisions of Agricultural and Food Chemistry, Biological Chemistry, and Medicinal Chemistry, Symposium on New Analytical Tools for Biological and Food Research, at the 102nd Meeting of the AMERICAX C h i m r x c A L SOCIETY, Atlantic City, N. J.
Microdetermination of Carbon in Steels Modification of the Standard Carbon-Hydrogen Train EARL W. BALIS, HERMAN A. LIEBHAFSKY, AND EARL H. WINSLOW Research Laboratory, General Electric Company, Schenectady, N. Y.
I
N JUSE, 1940, the Metallurgical Section of this laboratory asked the authors to determine low percentages of carbonin small samples of Nichrome for t h e purpose of establishing whether certain segregations formed in this alloy during service were carbides or nitrides. Since the amounts of carbon involved were far too small for the macrocombustion method, the authors developed a micromethod by introducing a quartz furnace into the standard carbon-hydrogen train ( 2 ) just before the Supremax combustion tube (universal filling). A modification of some sort is necessary because combustion in ordinary microanalysis occurs a t temperatures far below the minimum of 1100” to 1150” C. advisable in the case of steels. More recently, Smoluchowski (S) requested carbon determinations on small samples t o corroborate routine analytical results obtained in connection with experiments on the diffusion of carbon in steel. For this work, the authors modified the standard microtrain in another way-by slipping a furnace directly over the’first part of a standard quartz combustion tube.
10 minutes and to 1150’ C. in 25 minutes. The steel sample usually began to burn with a bright glow 3 or 4 minutes after heating was begun. After 30 minutes of heating time had elapsed, the current was interrupted, and the train was flushed for 20 minutes more. An oxygen flow of 5 cc. per minute was maintained for the entire 50-minute period; during the combustion of the larger samples, the rate a t which oxygen was introduced had to be increased in order to maintain this constant flow. Suitable blank corrections were determined from time to time on boats containing tin. These corrections, usually near 40 micrograms of carbon dioxide, were applied t o the analytical results, which are given in Table I.
The reliability of the method is shown b y the last three results, which were obtained on a standard low-carbon steel. Furthermore, the carbon content of the Xichrome samples
TABLE I. RESULTS WITH AUXILIARY COMBUSTION TUBE
Both modifications eventually gave satisfactory results and promise to be particularly useful when such carbon determinations are made only rarely, so that the setting u p of a special train is not warranted. The micromethod of Klinger, Koch, and Blaschczyk (1) requires a special train.
Sample 3 1SA 322D 3260 326A
Experimental AUXILIARYCOMBUSTION TUBE. The quartz auxiliary combustion tube (Figure 1) was calibrated with a thermocouple in the position of the boat, G. Standard microchemical technique was observed throughout except for the following details. Granulated tin served as accelerator. A weight of tin equal to half the weight of sample sufficed, although much more was occasionally added. Before steel samples were run, the train was conditioned by burning an unweighed primer of sugar in the conventional way. The auxiliary combustion tube mas heated to 900” C. in
327D 328C 329Fa 51690
5
(Small Xichrome samples) Sample Weight Tin
Carbon
.Mg.
MQ.
%
4.19 3.84 4.10 4.00 2.24 2.14 3.81 3.95 3.76 4.40 2.99 4.49 23.8 46.0 20.6
34 32 37 24 44 20 36 33 36 29 32 37 24 46 19
0.4 1.3 1.1 2.0 2.0 2.1 2.2 0.7 0.7 1.8 1.6 2.5 0.24 0.26 0.26
0.28% C by routine macromethod on this low-carbon steel.
January 15, 1943
ANALYTICAL EDITION
w FIGURE
ses h a d b e e n d o n e , it, proved' possible to compare the two methods b y measuring the deviations from a smooth curve drawn through the carbon contents of all t h e samples (Figure 2 ) . The accuracy of t h e Io results in Table I1 can 0 I 2 C M be summarized on the SCALE basis of the average diff e r e n ce b e t ween t h e 1. CROSS SECTIOS O F AUXILIARY(QUARTZ) COMBUSTION TUBE . _ amount of carbon found A . Bubble counter B . Impregnated tubing and the carbon content C . Corks faced with AI foil of the sample calculated D. Air jets E. Sichrome tape, 0.025 X 0.16 X 84 c m from the per cent obF . Gold foil baffles G. Porcelain boat tained on t h e s m o o t h H . 'Asbestas tape curve referred to above. I. Microcombustion tubc This average difference for the first ten results in Table I1 amounts to only 13 micrograms of carbon, in spite of the fact that absolutely uniform samples could not be obtained. If the worst value (0.488 per cent on Sample BIF) is discarded, the average difference for these ten results drops to 7 micrograms of carbon. The average difference between the carbon found and the true value for the Bureau of Standards sample is 3 micrograms of carbon. On the basis of the latter figure, 0.1 per cent carbon in a 100-mg. sample of steel can be determined within 10.003 per cent.
I
-
CARSON CONTENT IN */e
FIGURE 2.
69
W
TABLE 11. RESULTSFOR DIFFUSIONSPECIMEXS OF ORDINARY LOW-CARBON STEEL
PLOTOF GRAPHICALLY OBTAINED DEVIATIONS A
Sample
Micro results
A1F
0 Macro remlts
AlG ..i1H
paralleled the amount of the segregated phase shown b y the corresponding photomicrographs. This phase could have been only a carbide or a nitride, and nitrogen analyses proved this element t o be virtually absent. When the work was begun, devitrification of quartz and failure of the Xichrome heating units were expected; 20 hours of operation between 900" and 1150" C., however, did not impair the usefulness of the furnace. SLEEVEFURSACE.In the hope of simplifying the apparatus, a platinum-wound furnace (9 em. long) was constructed so that it could be slipped over the end of a standard quartz microcom-
bustion tube with 0.5-mm. clearance. During the combustion period, this furnace was placed 0.5 cm. from the entrance end of the long furnace in the microtrain; the sample boat was thus in the position prescribed for the regular carbon and hydrogen microanalysis. A platinum baffle and an air jet were used to protect the cork at the entrance of the combustion tube. With this sleeve furnace, 1150" C. \vas reached in 5 minutes and maintained for 25 minutes more; otherwise the manipulation was identical with that described above. The authors soon discovered that the standard quartz combustion tube (walls about 0.8 mm. thick) was too thin for operation at 1150" C. After one failure due to external devitrification, quartz of 1.5-mm. wall thickness was used for the first section of the tube; operation thereafter was satisfactory. The results obtained with the sleeve furnace are given in Table 11.
A2D
A2E
B. S.13'2"
Sample Weight
Tin
IMQ.
Mg.
%
70
17.15 106 5 25.97 inn 1
30 50 30 50 50 50 50 50 50 25 30 Rn 50
0.514 0 488 0 471 0 459 0 345 0 363 0 445 0 453 0 344 0 349 0 539 n 574 0.57i
0.501
ioi.9
105.0 105.6 102.2 104.9 49.90 14.12 102 .~ .
105.3 0
Carbon
lveraye Carbon
0.465 0 354 0 449 0 347
Bureau of Standards sample = 0.5737, C.
Summary 1. The standard carbon-hydrogen microapparatus can be readily adapted to the microanalysis for carbon in low-carbon steels or Nichromes. 2. In a 100-mg. sample of steel 0.1 per cent carbon can be determined within *0.003 per cent. 3. The method is particularly useful where only a few samples are to be analyzed at rare intervals. 4. KOattempt was made to speed up the determinations. 5. The usual quartz combustion tubes are not suitable for continued use a t 1150' C.
Literature Cited (1) Klinger, P., Koch, W., and Blaschceyk, G . , Angew. Chem., 53,
I n the analysis of the diffusion specimens, high accuracy was sought. Sincb t h e specimens for the microdetermination were taken from between others on which careful macroanaly-
537 (1940).
(2) Niederl, J. B., and Niederl, V., "Organic Quantitative Microanalysis", pp. 80-113, Niw York, John Wiley & Sons, 1938. (3) Smoluchowski, R., Phys. Rev. (in press).
