to convert platinum oxide to metal, and a correction is subsequently made for the amount of oxygen that has reacted with the metal. TYPICAL SETS
OF
DATA
Example 1. Analysis of Coked Cracking Catalyst Sample weight, 10.00 grams Total oxygen charged, 128.9 (STP) cc. System calibration with reactor a t 750" Trap at - 195", volume 180.0 cc. Trap at -Bo, volume 125.3 cc. Bulb B volume, 201.1 cc. Room temp., 28.0", p , i 6 0 mm. 1. After combustion, pressure readings were as follow: Trap at - 195", p 138 mm. ;= 29.6 (STP) cC. of gas present Trap at -78", bulb B in system, p 298 mm. ;= 116.1 (STP) cc. of eas oresent 2. Therefore 128.9 - 116.1 12.8 (STP) C C . Of 01 used to react with hydrogen 116.1 - 20.6 = 86.5 (STP) CC.of 0 2 used to react with carbon 3. Catalyst contains 0.463 wt. % C, 0.0228 wt. 7 0 H H/C atom ratio in coke 0.59 Example 2. Analysis of Coked Reforming Catalyst I
.
Sample weight, 9.99 grams Total oxygen charged, 63.6 (STP) cc, System calibration with reactor a t %OD Trap a t -195", volume 181.9 cc. Trap at -78', volume 130.6 cc. Room temp. 27.8", p 759 mm. 1. After combustion, pressure readings were as follows: Trap a t -195", p 51 mm. == 11.1(STP) cc. of gas present Trap a t - - 7 8 O , p 340 mm. 53.0 (STP) cc. of gas present 2. Hzused in final reduction, 9.4 (STP) cc. 3. Therefore
63.6 - 53.0 - '/z (9.4) = 5.9 (STP) cc. of 02 used to react with hydrogen 53.0 - 11.1 = 41.9 fSTP', cc. of 0 9 used to react with carbon 4. Catalyst contains 0.225 wt. 70 C, 0.0106 w t . 70 H H/C atom ratio in coke 0.56.
Precision of the method is good (Table I). For a series of samples having coke levels in the range 0.2 to 4 weight %, the standard deviation of the hydrogen determination \vas, on the average, 3.7% of the hydrogen content, and the standard deviation of the carbon determination was 2.0'3& of the carbon value.
Because standard samples of coked catalyst are not available, i t was not possible to check the absolute accuracy of the method in this xay. A sample of anthracene was analyzed by this method, after modification of the system to permit bringing the platinum spiral to temperature before heating the anthracene. Although recovery was not quantitative, because of condensation of some anthracene on the cooler portion of the system before the platinum spiral, the hydrogen-carbon atom ratio of the material burned was 0.71, an exact check of the true value. I n another attempt to establish the accuracy of the method, a series of silicaalumina catalysts, coked to levels between 0.3 and l%, was analyzed by both the proposed method and the conventional combustion procedure. Results are shown in Tahle 11. RECEIVED for review December 2 i , 1956. ilccepted July 19, 1957. Division of Petroleum Chemistry, 131st Meeting, ACS, Miami, Fla., April 1957.
Determination of Carbon, Hydrogen, and Nitrogen in Organoboron Compounds \
PAUL ARTHUR, RAYMOND ANNINO', and
W. PATRICK D O N A H 0 0 2
Department o f Chemistry, Oklahoma State University, Stillwater, Okla.
b Conventional combustion techniques, when applied to the determination of carbon in compounds containing boron-carbon linkages, yield unacceptably low carbon percentages. However, b y employing quartz combustion tubes and heating to high temperatures (IOOO" to I I O O O C.) in the unpacked section around the combustion boat, both carbon and hydrogen could b e determined with excellent accuracy and precision. Determinations of nitrogen in acetanilideboron trifluoride were improved b y restricting sample sizes to 7 mg. or less or b y employing a longer combustion tube with two successive permanent packings.
C
combustion techniques, when applied to organic compounds containing boron-carbon linkages, are known to give unacceptably low carbon values ( I , 12). PhenylOSVEKTIONSL
Present address, Northeast Louisiana State College, Monroe, La. 2 Present address, Monsanto Chemical Co., St. Louis, Mo. 1
1852
ANALYTICAL CHEMISTRY
boric oxide, for example, analyzed by combustion gives carbon percentages from 63.25 to 66.10 compared to the theoretical 69.34. Incomplete combustion is the reason for this, apparently, for when such results are obtained a black deposit, presumably boric oxidecoated carbon ( 1 ) or carbides of boron, remains in and around the combustion boat even after prolonged heating at the usual temperatures. The purpose of this research was to determine whether the higher combustion temperatures permitted by the employment of quartz combustion tubes would make the combustion of such compounds sufficiently complete for accurate analytical applications, particularly for carbon determinations. A similar approach to the analysis of organofluorine compounds, which like organoboron compounds are difficult to burn, has been reported (3, 4). APPARATUS
The combustion apparatus for nonnitrogenous compounds (Figure 1,A) is the same essentially as that described by Niederl and Niederl (9) except that a transparent fused quartz tube, 90 em.
long and 1.0 cm. in outside diameter drawn down at its exit end to a tip 3 mm. in outside diameter, is used for the combustion tube. Because metal oxides attack quartz rapidly a t the temperatures it was desired to employ, the packed portion of the tube was heated only to the customary 700' to 750" C., higher temperatures (1000" to 1100' C.) being employed only in the unpacked section around the platinum combustion boat. I n choosing and preparing materials ior packing the tube, the suggestions of Niederl and Kiederl (10) were followed. I n the determination of carbon and hydrogen in amine-boron trifluoride complexes it was necessary to provide means for removing the fluorine and possible oxides of nitrogen. The packing shown in Figure 1,B, was employed for such purposes. Although this diagram shows two lagers each of additional cupric oxide and platinized asbestos in the packing. these were !sed merely so the longer furnace employed (Sentry No. 23815) would be entirely filled with packed tubing. Evidence indicated that this was probably an unnecessary precaution. The sample burner is shown in Figure
2. The outside cylindrical casing, A . and cover, B, are constructed of aluminum with ends, E , of Transite. The heater coil, C, is made of 18 feet of Nichrome wire Brown and Sharpe No. 20 (0.67 ohm per foot); the space between the coil and the aluminum shell is filled with Celite to provide heat insulation. This sample burner was connected through a &ere ammeter to a 500watt Yariac a t points, F , and was calibrated by means of a thermocouple placed m-ithin the combustion tube.
ILf
U
U ' U
v
REAGENTS AND MATERIALS
A.
I?. C.
D. E. F. G. H. 1. J. K. L.
Figure 1 . Combustion tube packings Quartz combustion tube Platinum gauze Silver wire, Brown and Sharpe No. 30 wound loosely around a 3-mm. glass rod to form rolls to fill tube Asbestos plugs (1 to 2 mm. thick) CuO wire Platinized asbestos PbOz pellets Sentry electric furnace S o . 23815, Sentry Co., Foxboro, Mass. Heating mortar (filled xith p-cymene; boiling point, 175' to 178" C.) Sargent furnace, No. 5-36400 Asbestos choking plug (4 to 6 mm. thick) Quartz combustion tube, 60 X 1.0 cm. in outside diameter, with 3-mm outside diameter tip
Ascarite, 8 to 20 mesh. and Dehydrite, both from A. H. Thomas Co., Philadelphia. Pa., nere used in the carbon dioxide and water-absorption tubes, respectively, for determining carbon and h ydrogcn. Thr carbon dioxide used for the Dumas determination of nitrogen was a high purity quality of tank carbon dioside obtained from the Ideal D r y Ice X f g . Co., Ada, Okla. Blanks r u n employing this carbon dioyide showed that after small residual quantities of (presumablj-) air had been removed by bleeding the tank a t the rate of about 5 ml. per minute for 1 hour, the remaining carbon dioxide n as of excellent quality for Dumas deteririnations. The compounds employed for testing these procedures u-ere synthesized in this laboratory.
PHEMLBORIC ACID AXD PHEKYLOXIDE. Phenylboric acid was prepared by the method of Seaman and Johnson ( 2 2 ) . The acid dehydrated readily to the oxide; consequently, part of the product !vas converted to phenylboric oxide by placing it in a vacuum desiccator over activated alumina until the product reached constant \\-eight. The remainder was recrystallized from water and dried on the filter by dran-ing air through the mass. BORIC
I
>
12 CM.
Figure 2.
Sample burner
-4. Cylindrical casing I?. Cover C. Heater coil D. Celite E. Ends of cylinder F'. Electrical connections
Table I,
Compound Phenylboric acid Phenylboric oyide Tri-a-naphthylboron But:-lhoric acid Acet:tnilide-BFj
Results of Determinations
Element Detd.
Theoretical,
KO.of
70
detns.
C H
59.07 5 .i D 69.34 4.85 91.84 5.41 47.11 10.89 47.31 4.47 6.91
5 5 5 5 5
C H C H C H C H
s
-I
5 a 6 6 6
Experimental Dev. from Av., Mean % Av. Mas59.12 6.01 69.42 5.14 91.68 5.58 47.08 11.18 47.27 4.74 6.93
0.06 0.02 0.05 0.04 0.05 0.08 0.05 0.02 0.02 0.14 0.04
0.13 0.03 0.07 0.08 0.11 0.11 0.07 0.03 0.03 0.22 0.05
Even this treatment n ill el-entually, though very slowly, dehydrate sqme of the phenylboric acid; by withdran ing large samples a t different times and determining the moisture loss in dehydrating small weighed portions completely t o phenylboric ouide, a pure product was obtained in 2 hours. The phenylboric acid thus prepared had a melting point of 213-15' C. [216O c. ( 5 ) ; 21.5.5-19' C. ( 1 5 ) ] . The oxide melted a t 206-7' C. [190" C. (?')I. This coniby the method of ( 2 ) . I t s melting 203-04" C. [203C. (S)]. IIL-BUTYLBORIC ACID. This was produced by the method of Snyder. Kuck, and Johnson (14). -4fter recrystallization from toluene, it was dried in a stream of nitrogen a t room temperature for 10 to 14 hours and then analyzed. Immediate anal! sis and great care in handling were necessary because this compound dehydrates TRI-a-N.4PHTHYLBOROK.
pound v a s prepared Broan and Sefeshi point in vacuo, was 05" C. (6); 206-07"
VOL. 29, NO. 12, DECEMBER 1957
1853
readily and undergoes autoxidation on exposure to air (16). ACETANILIDE-BORON TRIFLUORIDE. A solution of acetanilide in chloroform was added to an excess of boron trifluoride dissolved in diethyl ether. The crystalline product was filtered, washed, while wet, with ether, and stored in vacuo over anhydrous calcium chloride for 48 hours before analysis. The product melted, with decomposition, a t 143" to 149" C. [133" C. with decomposition ( I S ) ] . PROCEDURE
The combustion tube was conditioned in a stream of oxygen for 24 hours, after which a few unweighed samples of benzoic acid were burned to restore moisture equilibrium and activate the platinum gauze. The furnace temperature was maintained a t 725" f 25" C. and the heating mortar a t the boiling point of p-cymene. The sample contained in a platinum boat was placed 6 to 7 cm. in front of the platinum gauze (Figure 1) and the sample burner was placed 2 to 3 cm. in front of the boat. For the analysis of relatively stable compounds such as phenylboric oxide, the sample burner temperature was adjusted immediately to 1000" C. The burner was left in its original position for 5 minutes and then slowly moved to the platinum gauze over a period of 15 minutes. Without further movement of the burner, heating was continued for 10 minutes (or until all black residue was gone) ; then the remaining gases were flushed out for 20 minutes more. The oxygen flow rate was maintained at 5 ml. per minute throughout the combustion, a total volume of 250 ml. being used. The absorption tubes were flushed with 50 ml. of dry carbon dioxide-free air, wiped in the usual manner ( l l ) and , weighed. For highly combustible compounds such as n-butylboric acid, the sample burner temperature was lowered to 300"
to 400" C. and the first burning completed, as described above, in 15 minutes. The burner was nioved back to its starting position and a second pass, requiring a period of 15 minutes with the burner a t 1000" C., oxidized any residue. The remainder of the operation was as described before, I n determining carbon and hydrogen in amine-boron triff uoride complexes, such as the acetanilide-boron trifluoride reported in Table I, the burning procedure was the same as that for phenylboric oxide; the combustion tube packing, however, was as illustrated in Figure 1,B. After 50 to i o runs on the complexes, the silver wire in the section after the platinum gauze was colored yellow and the quartz tube a t this point had become thin and fragile. It was necessary, therefore, to cut this portion out, fuse the good sections together, and repack the tube. When nitrogen was determined by the usual micro-Dumas method (8) but with 10- to 15-mg. samples, the results were high by about 1 part in 10. Therefore, the procedure was modified using a longer combustion tube with two permanent packings in sequence or when the conventional packing was employed, using 5- to 7-mg. samples and somewhat lower than usual burning rates. I n either case a little more free space (10 cm.) was provided ahead of the temporary packing, for such compounds have a tendency to volatilize back toward the mouth of the tube. The permanent packing of the Dumas apparatus is slowly rendered ineffective by amine-boron trifluoride compounds; consequently, if large samp1es-e.g., 10 mg.-are used, the packing usually needs to be replaced after 6 to 8 runs. Such deIeterious effects of halogen compounds on Dumas packings have been noted ( I S ) . RESULTS AND CONCLUSIONS
A study of the results given in Table I
shows that with all compounds used in this investigation, the accuracy and precision obtained for both carbon and hydrogen are highly acceptable, the results being comparable with those expected from ordinary organic compounds. ACKNOWLEDGMENT
The authors gratefully acknowledge the assistance of the Oklahoma A. and M. Research Foundation in obtaining the financial assistance needed to carry on the research described in this paper. LITERATURE CITED
Ainley, A. D., Challenger, F., J . Chem. SOC.1930, p. 2177. Brown, H., Sefeshi, S., J . Am. Chem. SOC. 70,2793 (1948). Clark, H. S., Rees, 0. W., Illinois State Geol. Survey, Rept. Invest. No. 169, (1954). Gel'man, N. E., Korsun, M. O., Doklady Akad. Nauk, S.S.S.R. 89, 685-7 (1953). Khotinsky, E., hfelamed, M., Ber. deut. chem. Ges. 42,3090 (1909). Krause, E., Xobbe, P., Zbid., 63, 934 (1930). Michalis, A., Becker, P., Zbid., 15, 180 (1882). Niederl, J. B., Niederl, V., ''MicrOmethods of Quantitative Organic Analysis," 2nd ed., pp. 79-95, Wilev. New York. 1942. Ibid., 101-16. ' Zbid., pp. 107-12. Zbid., pp. 123-4. Seaman, W., Johnson, J. R.,J . Am. Chem. SOC.53,715 (1931). Shelberg, E. F., ANAL. CHEM.23, 1492 (1951). Snyder, H. R., Iiuck, J. A., Johnson, J. R., J . Am. Chem. SOC.60, 105 (1938). Zbid., p. 108. Sugden, S., Waloff, M., J . Chem. SOC.1932, p. 1496.
pi.
RECEIVEDfor review July 19, 1957. Accepted August 7, 1957.
Determination of Carbon Dioxide in Gas Streams PAUL
E. TOREN
Phillips Pefroleum
and B. J. HEINRICH
Co., Bartlesville, Okla.
b A
method has been developed for determination of carbon dioxide concentrations ranging from 1 p.p.m. to 100% in a gas stream. The sample to be analyzed is passed through a saturated solution of an alkaline earth carbonate containing excess solid carbonate. At equilibrium, the pH of the solution is measured and the carbon dioxide content of the gas is determined from a previously prepared calibration chart. The method is precise to within =k5% of the carbon di-
1854
ANALYTICAL CHEMISTRY
oxide content measured. The procedure can be easily adapted to provide automatic recording and control of the carbon dioxide content of a gas stream.
T
of carbon dioxide on the solubility of calcium carbonate in water has been known since the time of Cavendish and has been studied by a number of workers (2), but this phenomenon has not been applied to continHE effect
uous determination of the carbon dioxide content of a gas. Measurement of the acidity of a carbonate-bicarbonate buffer in equilibrium with a gas has been used to determine the carbon dioxide content of the gas ( I ) , but this particular procedure was applied to only a limited range of carbon dioxide concentrations. Consideration of the equilibrium relationships which must be satisfied in a saturated solution of calcium carbona!e shows that, if a solid carbonate phase :is
