experiments a .daides:; >tee1 U-tube \\-as employed in the hope that t'he adxorption of water on the ~ a l l sof the t,nbe would be less of a problem on this material than on glass. Holvever, in no case was a stable reading obtained any faster, nor n-as the firm1 reading significantly different froin that obtained ming tho glass F-t'ubci. RESULTS AND CONCLUSIONS
Typiczl data obtained in a deterniination of residual moisture are given in Table I, for t,liree runs on anhydrous magnc,siuin pcrchlorate. -1sumniary of the results on variow drying agents is given in Table 11, the drying agents being lidcd in t,he rrrtivr of their efficienc !-. 1.: a clr.-iccant, anh;,-drousmagnesium perchlorate is iri a el I5 times: as much Tater being left in a gas stream by the ncxt best desiccant, barium oxide. This .fficirnc:y, coupled with eahe of handling and capncity unmatched by any of the otlier desiccants, makes anhydrous magnesium perchlorate the desiccant of rhoice. The coninion practice of following Ascarite and AIikohhite vr.ith a desiccant in U-tubes in which these materials are used as absorbents for carbon dioxide is confirmed by the fi:idings that these material.? arc poor dr? ing agents. In accord 11-ith the findings of Morley ( I @ , a nc~gligihleweight of phosphorus pentoxide was vapor. zed when used as :t desiccant a t 25' C. to dry a gas stream. H o w w r . contrary i n Norley, a dis-
tinctly measurable amount of wate'r remained in the gas s t r m n . Readings obtained with the 1Ioi.ture Illonitor departed widely from the values for the residual water obtained by the liquid nitrogen-freezing-graT imetric method just described; tliu., for anhydrous magnesium perchlorate. reading 3.3 fig. of water per liter (0.17 pg. of water per liter by the grai imetric method); Anhydrone 4.6 (1.5); barium o d e : 2.0 (2.8); phosphorus pentoxidc. 2.4 (3.5); I\lolecular Sieve 5-4: 2.4 (3.9); lithium perchlorate: 21 (13): calcium chloride, anhydrous: 9 (67) ; Drierite: 113 (67); silica gel: 133 (70'1; calcium chloride (CnCI2.0.28 H20): 111 (99) ; Anhydrocel : 503 (207) ; barium perchlorate: 98 (599) ; calcium oxide: 3.7 (656); liquid nitrogen trap (helium used a5 carrier ga.): 1.7 (reference). Readings of zero were not obtained on the Aloisture Monitor rvhen phosphorus pentoxide iva4 tested nor when liquid nitrogen trap TI as u-ed to dry the entering gas. Thus, in our hands the Moisture Monitor has proved unreliable for the measurement of the small amounts of water remaining in a gas stream dried with a chemical desiccant. LITERATURE CITED
(1) Baxter, G. P., Starkweather, H. IT., J . Bm. Chem. SOC.38, 2038 (1916). (2) Baxter, G. P., LJ-arren, R. D., Ibid., 33,340 (1911). (3) Berzelius, J. J., Dulong, P. L., A n n . Chim. Phys. Sei-. 15, 385 (1820;.
(4) Booth, H.
S , NcIntyre, L , I A D
, AAAL
E D . 2 , 12 (1930). ( 5 ) Bower, J. H , J . Iiea Vatl. Bur. Std. 12.241 119S4). (6) Dibbits, H. C., Z. A n d . C'heni. 15, 150 (18i6). ( 7 ) Dover, M. I-., llarden, J. IV., J . A m . Chem. Sac. 39, Id09 (1917). 18) Dumas. A. B.. Ann. Chim. Phvs. 9er. ~~, 3, 8, 193,'210 (1842). (9) Erdmann, 0 . L., Marchan?, R. F., J . I'rak. Chem., 26, 464 (1842,. (10) Favre, h f . P.-*4., A n n . C'him. I'hys. Fer. 3, 12, 223 (1844). (11) Fresenius, R., 2. Anal. ('hem. 4, 177 (1865). 112) Hammond, IT'. 1., Kithrow, J. It., Ind. Eng. Chem. 25, 653 (1933'8. (13) Johnson, F. 11, C., J . Am. ( ' h e m . SOC.34, 911 (1912). (14) llorley, E. IT.,d m . J . Sei. Per. 3, 30, 1-10 (1885). (15) hlorley, E. W., Zbid., Per. 3, 34, 199 (1887). (16) Morley, E. W,, J . Am. Cheifl. Soc. 26, 1171 (1904). (17) Pett,enkofer, >I.,Ann. Chew., Suppl. 2, 29 (1862); Sitzungsber. kiin. hnyerischen Akad. Il'iss. Jfiinchen. 11, 59 (1862). (18) Regnault, M. V., A n n . Chitn. Phys. Ser. 3, 15, 152 (1845). (19) Smith, G. F., Ind. Eng. Chem 19, 41 1 (1927). (20) Smith, G. F., Brown, lI., Ross, J. F., Ibzd., 16, 20 (1924). (21) Taylor, E. C., Rejrzg. Eng. 64, SO. 7,41 (1956). (22) Kalton, J. H., Rosenblum, C. IY., J . Am. Chem. SOC.50, 1648 (19% 1. (23) Washburn, E. IT.,Nonthly T e a t h e r Rev. 52, 488 (1924). (24) Willard, H. H., Smith, G. F., J . Am. Chem. Sac. 44, 2255 (1922'.
ESL. CHEM
RECEITED for reviex October 12, 1962. Accepted February 1.3, 19ti8. This work was done under a grant from the Xational Science Fonndation, XSF-GI 0012.
Anodic CIxidation of Triethylamine ROLAND F. DAPO (2nd CHARLES K. MANN Department of Chemistry, Florida State University, Tallahassee, Flu.
b The oxidation of triethylamine at a platinum anode has been investigated in dimethylsulfoxide with a Pb-Pb(ll) reference electrode. Coulometric analysis indicates that 1.02 0.04 electrons per molec:ule are involved in the reaction. Ail examination of chronopotentiometric data indicates that the electrode rc?action i s diffusion controlled and involves a reversible charge transfer followed b y an irreversible chemical reciction. The major product of the reaciion i s the triethylammonium ion, which was identified by preparing its picrate!. The postulated reaction mechanism involves loss o f an electron to form the radical ion, followed b y reaction with the solvent to form the triethylammonium ion. Quantitative analysis can b e performed under optimum conditions with a relative standard deviation of 2y0.
S
of the electrocliernical reactions of amines that have been reported to the present generally involve aqueous systems. The amine group is sufficiently difficult to oxidize that it is generally necessary for a favorable form of the reaction product to be available if the reaction is t o be observed in aqueous solution. For example, the ortho and para isomers of phenylenediamine are readily oxidized to the corresponding imines, n hile the meta isomer, having no quinoid ring structure available, is relatively difficult to oxidize ( 2 ) . Anodic oxidations of amines apparently involve abstraction of one of the unshared pair of electrons from the nitrogen atom, followed by some chemical rearrangement. On this baqis, it seems reasonable to expect that oxidations of amines should generally be possible, but in the case of a compound TUDIES
that lacks a favorable structure, higher potentials than are available in aqueous systems might be necessary. In addition, it has been pointed out that the compound must be available as the free amine if the reaction is to be carried out smoothly ( 7 ) . Loveland and Dimeler (51 have given peak potentials for voltammetric oxidation of some ahphatic amines in acetonitrile, but have not reported any investigation of the electrode reactions. \Ye have examined the oxidation of several aliphatic amines in various nonaqueous solvents and nish to report on a detailed investigation of the reaction of triethylamine in dimethylsulfoxide (DMSO). This has involved an examination of the chronopotentiometric behavior of the system, the performance of preparative and coulonletric controlled VOL. 35, NO. 6 , MAY 1963
a
677
potential electrolyses and a chemical examination of the reaction mixture. EXPERIMENTAL
Reagents. The triethylamine used was Matheson Coleman and Bell (b. p. 88" to 90" C.). Vapor phase chromatographic examination indicated only trace impurities. Titration with HC104 in glacial acetic acid gave a purity of 100.2 0.3%. DMSO was vacuum distilled, that portion coming over a t 47" a t 3 mm. Hg being taken for use. Solutions of lead nitrate in DMSO were dried by stirring under vacuum. All other chemicals were reagent grade and were used without further purification. Chronopotentiometric Experiments. The conventional three-electrode system, with transistorized constant current source (6), potentiometer recorder, and external bias was used. The working electrode was a 1.19 sq. cm. platinum disk, fitted with an approximately 1-mm. lip, positioned for upward diffusion to avoid erratic behavior due to convection (1). Tern; perature was controlled a t 25.0 0.1 C. Satisfactory results were obtained using XaC101, KSOI, or P b ( S 0 3 ) ~ as supporting electrolyte. Cell resistance through the working and auxiliary electrodes was about 300 ohms with a DMSO solution 0.1P in Pb(WO&. For all of the experiments reported here, the reference electrode sy-tem was the Pb-Pb(I1) couple. A typical chronopotentiogram is shown in Figure 1. The electrochemical behaviors of the Pb-Pb(I1) couple and the Ag-Ag(1) couple in DhISO have been examined to evaluate their use as reference electrodes. I n both cases cathodic and anodic chronopotentiograms were run, using the apparatus described above, with NaC104 supporting electrolyte and fiber type SCE reference. Cathodic electrolysis with the Ag couple, resulting in deposition of silver metal on the Pt disk, gave curves for which the log 71 * - t1'2 us. E was linear. On reversing the current, the anodic transition time was identical with the previously observed cathodic transition time. Log ( 7 1 1 2 - t'@)/t1/2 us. E gave linear curves for the anodic electrolysis. From the slope a value of n of 0.97 was obtained. These results indicate that the Ag-Ag(1) couple behaves reversibly, as expected, and that our apiiaratus and technique are capable of giving meaningful results in this system. In the case of Pb, reduction onto the P t electrode gave chronopotentiograms for which the log ~ 1 ' 2 - t 1 / 2 vs. E curves were not linear. The deposit was of a granular nature. Reverse electrolysis removed some, but not all of the deposited lead, as indicated both visually and by the fact that the anodic transition times were shorter than the cathodic transition times. We conclude that the Pb-Pb(I1) couple is chemically reversible in this system, but that the reaction may be kinetically sluggish since a nonlinear log transition time us. E plot is obtained for re-
::] 1.9
*
*
678
ANALYTICAL CHEMISTRY
I
0
IS
30
48
BO
75
TIME (SEC.1
Figure 1. Chronopotentiogram of 34.8mM triethylamine in 0.1 FPb(No& in DMSO at a current density of 0.842 ma./ cm2. The €114 is 1.470 volt vs. Pb-Pb(ll)
duction. To evaluate further the behavior of the Pb-Pb(I1) couple for use as a reference electrode, its potential in DMSO solution, us. SCE, was measured for several lead concentrations and found to be stable and reproducible within expected experimental error, using a voltage measurement with approximately one megohm input impedance. It was, accordingly, used as reference electrode, as mentioned above. Pretreatment of the working electrode prior to each chronopotentiogram was necessary in order to obtain reproducible results. This consisted of cathodic electrolysis, followed by chromic acid cleaning. In a series of runs on a single solution, the first was always rejected. Coulometric Experiments. The apparatus consisted of a potential controller similar to t h a t described by Kelly, Jones, and Fisher (S), and a hydrogen-nitrogen coulometer (4). Since the over-all reaction is irreversible, an undivided cell was used with a P t gauze anode, a mercury cathode, and a lead reference electrode poised with Pb(N03)z in solution. Satisfactory results were obtained with 0.1008' Pb(NOa)z supporting electrolyte. Pb(I1) poises the reference electrode, acts as supporting electrolyte, and reacts a t the cathode, but is without discernable effect on the anodic reaction. The following electrolysis procedure was used. Fifty-milliliter volumes of D-11SO-Pb(S03)2 supporting solution were pi-e-electrolyzed a t 1.70 volts us. Pb-Pb(I1) until a limiting current was reached. Current varied during the pre-electrolysis from approximately 1.4 to 0.7 ma. Then 0.001 mole of triethylamine in 5 ml. of DMSO-Pb(N0s)2 solution was added and the electrolysis continued a t 1.70 volts us. Pb-Pb(I1). The initial electrolysis current of approximately 570 ma. decayed to about 0.6 ma. The change in reference electrode potential, due to change in Pb(I1) concentration during the course
of the electrolysis amounted to about 3 mv. With this arrangement, a cell resistance of about 45 ohms was observed. An average of 1.02 i 0.04 electrons per mole was determined from three replicate electrolyses. Preparative Electrolysis. To obtain reaction products for identification, a n electrolysis was carried out as described above except with tenfold increase in the concentration of amine and supporting electrolyte. Increasing the concentration of P b ( I I ) , to permit larger scale electrolysis, caused a change in reference electrode potential of 15 mv. RESULTS
Chemical Identification of Products. The reaction mixture was examined by distillation and by extraction of the nitrogen-containing products. A solid derivative of the major product was prepared and compared with a control sample. The electrolyzed solution contains no appreciable concentration of compounds more volatile than DMSO. On making the mixture basic, hon-ever, aniine compounds could be distilled and determined by the Kjeldahl method. The results are shom-n in Table I for analysis of the reaction mixture and for analysis of a control consisting of a DMSO solution of Pb(KO3)2 Kith a known amount of triethylamine added. The control $vas carried through the same procedure as the other samples, except for the actual electrolysis. While base was added to the control in order to retain the identical procedure used with the electrolyzed samples, it is not necessary to add base to volatilize triethylamine from DMSO-Pb(N03)z solution. As might be expected from its boiling point, triethylamine evaporates rapidly from this solution a t room temperature.
Table 1.
Results of Analysis for Alkylammonium ton
Recovery of amine, Sample Control
MelJhod
70
Distillation
100.2 100.0 98.1 90.1 91.9 93.4 102. 96.8 96.8 87.0 89.4 87.8 88.8 88.8 82.1 83.3 79.6
Electrolyzed, No. 2
Ilistillation
Control
Extrzction
Electrolyzed,
ExtrmAion
Electrolyzed,
Extraction
Electrolyzed,
Extr:tction
No. 1 No. 2
No. 1 for 3 ” Amine
Variation of io+/2 with Current Density (Concentration of triethylamine 24.1 ivi31)
Table II.
Current density, 20,
ma. cm.l 0.211 0,424 0,846 1.69 2.05
Transition time, see. 508. 11s. 31.5 8 . 10 5.40
i0T1‘*,
ma., sec.1/2
4.76 4.60 4.74 4.82 4.76 Av. 4.73 f 0.06
After removal of the lead by sulfate precipitation t o facilitate subsequent separation of the phases, and making the solution basic, the nitrogen compounds were extracted iiito chloroform. Total amine was detc rmined by titrating the chloroform extrwt in glacial acetic acid \\-ith perchloric acid. Tertiary amine was estimated in the presence of primary and secondary amines by treating the extract with acetic anhydride prior to titration. Data are shown in Table I for analyses of two reaction mixtures, produced from separate electrolyses, and for a control. The control consisted of an ic’entical sample of amine in DMSO-Pb(NOa)2 solution n hich was carried through the entire procedure, except for the electrolysis. By either the distillation or the extraction procedures, approximately 90% of the original amine is recovered from the reaction mixture in a form titratable as amine, primary, secondary, or tertiary. Furthermore, approximately 80% of the original amine is present in the reaction mixture at3 a tertiary amine salt. The major component of the reaction mixture, the triethylammonium ion, was
identified by preparing its picrate salt and comparing it with triethylammonium picrate similarly prepared (9). Melting points for the triethylammoniuin picrate and for the picrate of the unknown compound were 170” and 171’ C., respectively (uncorrected). The literature value is 173”. The equivalent weights of the two picrates were determined by titrating with perchloric acid in glacial acetic acid. Both the unknown and the control gave values of 331 ; the actual value should be 330. Evaluation of Chronopotentiometric Data. An electrode reaction can be demonstrated to be diffusion controlled, hence not subject t o kinetic complications prior t o the electrode reaction, by showing t h a t when a series of chronopotentiograms is obtained under conditions of constant concentration and varying current denis constant. sity, the product, i&2, “io” is current density and “7” is transition time. The data in Table I1 show that this is true over a tenfold range of current densities. The upper limit of transition time for this series of esperiments n-as marked, not by failure of diffusion control, but by a visible spilling of the diffusion layer over the glass lip of the disk electrode. Presumably longer transition times could be attained by using an electrode with a deeper lip. Reinmuth has described procedures for treatment of chronopotentiometric data in order to elucidate electrode reaction mechanisms (8). Data for this t y e of evaluation have been obtained for the oxidation of triethylamine. Results from a series of chronopotentiograms recorded for a single solution are prevnted in Table 111. From these data, the diagnostic criterion d&4/b log io, is found to be 0.420 f 0.054 volt by least squares evaluation of the curve of E , vs. log io. I n Table IV, results from chronopotentiograms recorded a t constant current density for a series of solutions of varying concentration are given. The slope of a plot of E1,4us. log C is 0.135 =k 0.010 volt. Plots of E zw. log T~~~ - t 1 I 2 for all of the curves of Table I11 yield an average slope of 0.170 5 0.024 volt. A similar treatment for all of the curves of Table IV yields a slope of 0.151 =k 0.017. Chronopotentiograms were recorded for a series of solutions of varying concentration in order to illustrate the application of this reaction to quantitative analysis. The results are shown in Table V. Current reversal chronopotentiograms gave a reverse transition time of zero, indicating that the over-all reaction is irreversible. DISCUSSION
On the basis of the chemical identification of reaction products, the over-all
Table Ill.
Variation of El/4 with Current Density
(Concentration of trimethylamine, 38.3mM) Eli4
Current deneity, io, ma./cm.a 1.69 1.13 0.843 0.562 0.423
m
=
us.
Pb-Pb(II), volts 1,599 1.520 1.451 1.412 1,340
0.420 f 0.054 volt
Table IV.
Variation of Concentration
E114
with
(Current density, io, 0.842 ma./cm.z) Etir US.
Concentration of triethylamine, m,ld
Pb-Pb( 11),
8.53 16.7 34.8 71.7 119.
1,565 1.517 I .470 1,430 1.412
volts
m = 0.135 zt 0.010 volt
Table V.
Variation of Concentration
+/C
with
(Current density, io, 0.842 rnaJcm.2) Concentration of triethyl- Transition d/*/C‘, amine, time,’.r, sec.l/2/ mM see. mM 2.40 9.90 31.5 57.9 382, 1337.
6.78 13.3 24.2 33.9 79.5 146.
0.229 0.236 0.232 0.224 0.246 0.251
Av. 0.236
&
0.048
reaction results primarily in protonation of triethylamine. T h k occurs through the following steps: Et3N: EtaN+
*
+ e-
+.
+ (CHs)*SO .Eta”+ +
(1)
+
CHzSOCHa (2)
This is supported by the fact that in the coulometric experiment, the electrolysis current decayed to the background of the pre-electrolysis after pasqage of the equivalent of 1.02 electrons per mole of amine. Chemical identification of triethylammonium ion corresponding to approximately 80% of the starting material excludes the possibility of dimerization as a major reaction step. I n evaluating the reaction mechanism, one can consider, in addition to these results, the diagnostic criteria suggested VOL. 35, NO. 6, MAY 1963
679
by Reinmuth (8).These consist of the slopes of the plots of log ( ~ 1 ’ 2 t 1 ’ 2 ) / t 1 ’us. 2 E or log T ~ -’ t~1 I 2 vs. E for which we obtained 0.160 volt; of Ell4us. log io, for which 0.420 volt; of us. log C, for which 0.135; and of the ratio of cathodic to anodic transition times, for which rve obtained zero. In the discussion below-, we shall assume the two-step reaction scheme 01 electron transfer follon-ed by radical reaction mentioned above, and shall consider the kinetic schemes suggested by Reinmuth. If the electron transfer step is irreversible. then the nature of the second step will have no effect on the chronopotentiometric behavior. This would correspond to cases 3 or 6, which involve equal slopes for each of the log plots. Aipparently Tve are not dealing with these cases. The failure to obtain reverse transition, together with the chemical evidence and the log plot slopes appear to rule out cases 1, 2, 4, 5, 7 , 11, and 12. which involve reversible electron transfer reactions or reversible electron
transfer reactions followed by a reversible chemical reaction. Case 14 is excluded by failure to obtain the correct ratio of log plots. The fact that this would involve a nonintegral number of electrons, together n i t h the fact that dimerization is not observed, eliminates this possibility. Similarly, the absence of dimerization appears to eliminate cases 13 and 15. Case 9, rapid reversible electrode reaction followed by rapid irreversible chemical reaction, is ruled out by requirement of equal log plot slopes. On examination, our results appear to eliminate all of the suggested schemes except numbers 8 and 10, rapid reversible electron transfer followed by slow reversible chemical reaction and rapid reversible electron transfer followed by slow irreversible chemical reaction. One would not expect, however, to find that the reaction of this ion-radical with the solvent would be reversible; consequently case 8 is improbable. I t therefore appears that, of the suggested
schemes number 10, reversible electron transfer followed by an irreversible chemical reaction is most probable. LITERATURE CITED
Bard, A. J.,
~ A L C . H E v . 33, 11 (1961). ( 2 ) Elving, P. J., Krivis, -1.F., I b t d . , 30, 1645 (1958). ( 3 ) Kelly, >I T., . Jones, H. C., Fisher, D. J., Ibid., 31,488 (1959). (4) Lingane, J. J., 3‘Electroanalytical Chemistry,” 2nd ed., p. 456, Interscience, New York, 1958. ( 5 ) Loveland, J. K., Dimeler, G. R., ANAL. CHEM. 33, 1196 (1961). (6) Mann, C. K., Champeaux, V. C., J. Chem. Ed., 38, 519 (1961). ( 7 ) Mezoguchi, T., Adams, R. S., J . A m . Chem. SOC.84. 2058 11962). (8) Reinmuth, K. H., AX~L.CHEW32, 1514 (1960). (9) Shriner, R. L., Fuson, R. C.,,Curtin, D. Y., “The Systematic,,Identification of Organic Compounds, 4th ed., p. 229, Wiley, New York, 1956.
(1)
RECEIVEDfor review August 20, 1962. Accepted March 8, 1963. Work supported by the Petroleum Research Fund of the American Chemical Society.
Spectrophotometric Determination of Hydrocarbon and Carboxylic Acid for the Material Balance Data in Carbanion Oxidations HARVEY POBINER,’ THOMAS J. WALLACE, and JOHN E. HOFMANN Analytical Research Division and Process Research Division, Esso Research and Engineering Co., P.O. Box 727, linden, N. j .
b Analytical methods have been developed for obtaining material balance data in certain carbanion oxidation reactions. One method is an extraction-ion exchange-infrared technique to measure starting material and carboxylic acid product. The other method is an extraction-ultraviolet technique to measure aromatic starting material and carboxylic acid. The two methods are illustrated with mixtures of toluene and benzoic acid and 2methylnaphthalene and 2-naphthoic acid in solvent systems of base, dimethylsulfoxide, and water. Aliphatic compounds can also b e determined quantitatively.
E
ion exchange, and spectrophotometry are used in an analytical scheme for the quantitative analysis of carbanion oxidation products. The technique was developed for determining both conjugated and nonconjugated carboxylic acid products and unreacted hydrocarbon in basic solutions. It was extensively used for 680
XTRACTION,
ANALYTICAL CHEMISTRY
obtaining material balance data in a general study of the base-initiated oxidation of carbanions in selective solvents (2, 15). Carbanion oxidations are thought to involve proton abstraction by base in selective solvents. Molecular oxygen then reacts with the carbanion to form Oxidation products by an anion-radical mechanism. This mechanism and certain experimental data have been described (2, Q-li?.15). Tmo procedures are discussed. One is an extraction-ion exchange-infrared procedure for starting hydrocarbon and a carboxylic acid derivative in a system of solvent, base, and water. This method is indicated for either conjugated or nonconjugated hydrocarbon and acid. The other is an extractionultraviolet procedure for a conjugated starting material and its carboxylic acid derivative in a similar system. Both of the procedures rely on the initial removal of unreacted starting material by an extraction step with cyclohexane. This effectively removes any spectral interference with the sub-
sequent determination of carboxylci acid. The carboxylic acid is present as the potassium salt in the solvent, dimethylsulfoxide (DMSO). Hydrochloric acid is added to liberate the carboxylic acid in solution. The HCl also prevents the hydrogen bonded adducts that are reported to form betneen weak acids and polar solvent systems (S, 4, 6-8). If the carboxylic acid that remains in the aqueous raffinate is aromatic, it iq directly determined by ultraviolet spectrometry. If the carboxylic acid that remains in aqueous raffinate is aliphatic. or only presents weak ultraviolet absorption, it is determined by an ion exchangeinfrared method. This involves treating the aqueous raffinate Kith Amberlite LA-2, an anionic exchange resin. The Amberlite-RCOOH adduct forms and is extracted with carbon tetrachloride. The extracted carboxylic acid is then
1 Present address, General Precision Aerospace Group, 1225 McBride Avenue, Little Falls, N. J.
