osmium in the 1:2 complex, the postulation of the structure appears complicated. The reaction of the reagent with hexavalent osmium prepared by the reduction of alkaline solution of the tetroxide with ethanol, leads to the formation of the same complex as is evident from the same region of maximum absorption of the color system and its identical tolerance to acidity. It is unlikely that cationic complex contains osmium in the oxidation state 6. Therefore the tetravalent state seems more probable. ACKNOWLEDGMENT
The authors are thankful to G. P. Chatterjee and H. N. Ray for their encouragement and interest.
LITERATURE CITED
(1) Allan, W. J., Beamish, F. E., ANAL. CHEM.24, 1608 (1952). (2) Ayres, G . H., Wells, W. N., Zbid., 22, 317 (1950). ( 3 ) Beamish. F. E.. Takznta 12. 789 (1905). ’ (4) Beamish, F. E., McBryde, W. A. E., Anal. Chim. Acta 18, 55 (1958). (5) Hillebrand, W. F., Lundell, E. F. Bright, H. A., Hoffman, J. I., “Ap jied Inorganic Analysis,” p. 354, d l e y , New York, 1953. ( 6 ) Job, P., Ann. Chim. (Pam‘s), [ l o ] 9, 113 (1928).
.~,
(7) Majumdar, A. K., Chakrabartty, M. M., Anal. Chim. Acta 20, 379, 386
(1959). (8) Ma’umdar, A. K., Chakrabartty, M. M., %.Anal. Chem. 162, 101 (1958). ( 9 ) Ringbom, A., Z. Anal. Chem. 115, 332 (1938). (10) Sandell, E. B., “Colorimetric Determination of Traces of Metals,”
3rd ed., p. 699, Interscience, New York, 1959. (11) Van Allan, J. A., Deacon, B. D., “Organic Synthesis,” Vol. 30, p. 56, Wiley, New York, 1950. (12) Vosburgh, W. C., Cop er, G . R., J. Am. Chem. Soc. 63, 437 f1941). F. J., “Organic Analytical (13) Welch::, Reagents, Vol. 4, p. 127, Van Nostrand, New York, 1948. (14) Xavier. J., Z. Anal. Chem. 164. 250 (1958j. (15) Yoe, J. H., Jones, A. L., IND.ENG. CHEM.,ANAL.ED. 16, 111 (1944).
B. C. BERA M. M. CHAKRABARTTY Research and Control Laboratory Durgapur Steel Plant, Durgapur 3 West Bengal, India. The financial su port of the Council of Scientific and Incfktrial Research (India), New Delhi is gratefully acknowledged.
Rapid Spectrophotometric Method for Formaldehyde Detection SIR: Our laboratory has been concerned with the determination of leakage of low aqueous concentrations of formaldehyde, in the presence of ethyl alcohol, across an O-ring seal. Because of the large number of tests required, a procedure was necessary which would be rapid without sacrificing accuracy. In order to quantitatively measure these low concentrations of formaldehyde, a simple modification of the Hehner (4) test for formaldehyde in milk has been developed. Proteose peptone, when added to the sulfuric acid/ferric chloride solution recommended by McLachlan (6),produces a violet color which adheres to Beer’s law in the range of 0 to 3 p.p.m. formaldehyde. EXPERIMENTAL
Apparatus. Absorbance measurements were made a t 550 mp with a Bausch and Lomb Spectronic 20. A spectral scan on a Bausch and Lomb Spectronic 505 determined the wavelength setting. Reagents. H2SOa/FeCla solution was prepared by dissolving two parts FeCla in 10,000 parts concentrated H,SO,; 3% proteose peptone; formaldehyde standard solutions of 0.1, 0.5, 1.0, 2.0, and 3.0 p.p.m. were prepared in 0.5% sodium meta bisulfite. Procedure. Two milliliters each of test solutions, standards, and a blank of 0.5% sodium meta bisulfite are pipetted into separate borosilicate glass test tubes to which 2 ml. of ‘H2S04/FeC18 solution are added. .After mixing, 2 ml. of 3% proteose peptone are added and thoroughly mixed with the other reagents. The tubes are placed into a boiling water bath for 5 minutes, allowed to cool for 15 minutes and then read spectrophotometrically.
RESULTS AND DISCUSSION
Color Stability. Although readings are made at fifteen minutes, t h e violet color is stable up to one hour. Comparison with Other Spectrophotometric Tests for Formaldehyde. The proteose peptone test has been compared with the chromotropic acid method of Frise11 and MacKenzie (3) and the colorimetric procedure of Sawicki and Hauser (7) in the range of 0 to 3 p.p.m. of standard formaldehyde solutions. The results have checked within 0.1 p.p.m. The proteose peptone method has a significant time advantage when compared with these other methods. The method of West and Sen (8) is as rapid and as sensitive as the proteose peptone method. However, since their method requires a sulfuric acid concentration of about 90yo,the formaldehyde sample must be diluted considerably. Thus, the accuracy of this chromotropic acid method for low concentrations of formaldehyde is less
than the proteose PeDtone method, particularlsf an instriment such as the Bausch and Lomb Spectronic 20 is used. Interferences. Acetaldehyde, butyraldehyde, propionaldehyde, ethyl alcohol, and diacetone alcohol were tested and found not to react with proteose peptone nor with chromotropic acid. The chromotropic acid results agree with the work of Eegriwe ($), MacFadyen (6) and Bricker and Johnson ( I ) . However, when low concentrations of these substances were tested in the presence of formaldehyde, with the exception of ethyl alcohol, they were found to interfere with the color development of the modified Hehner test but not with the chromotropic acid procedure. Recovery of formaldehyde from aqueous solutions of these substances is shown in Table I. On the basis of these recovery studies, the proteose peptone test is a rapid, accurate method for measuring low aqueous concentrations of formaldehyde in the absence of interfering substances.
Formaldehyde Recovery from Aqueous Solutions of Aldehydes and Alcohols HCHO Recovered, p.p.m. Modified Chromotropic 1 p.p.m. 50 p.p.m. Hehner acid HCHO Acetaldeh de 0.55 1.01 HCHO But yraldexyde 0.43 0.97 HCHO Propionaldehyde 0.19 0.97 HCHO Ethyl alcohol 1.01 1.00 HCHO Diacetone alcohol 0.73 0.97 0 . 5 p.p.m. 5 p.p.m. HCHO Acetaldehyde 0.46 0.47 HCHO Butyraldehyde 0.20 0.47 HCHO Propionaldehyde 0.17 0.47 HCHO Ethyl alcohol 0.49 0.48 HCHO Diacetone alcohol 0.45 0.47
Table 1.
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VOL. 38, NO. 10, SEPTEMBER 1966
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ACKNOWLEDGMENT
The technical assistance of Judith Bushay and Gloria McKinley is gratefully acknowledged.
LITERATURE CITED
(1) Bricker, C. E., Johnson, H. R., IND. ENG.CHEM.,ANAL.ED. 17, 401 (1945).
2. Anal. Chem. 110, 22 (1937). (32,Fruell, W. R MacKenzie, C. .G Methods in B!ochemical Analysis,;’ Vol. VI, 63-77, IMerscience, New York, 1959. (4)Hehner, O.,Analyst 21, 95 (1896). (5) MacFadyen, D. A., J. Biol. Chem. 158, 118 (1945). (6)McLachlan, T., Analyst 60, 752 (1935). (7)Sawicki, E., Hauser, T. R., ANAL. CHEM.32, 1435 (1960). (2) Eegriwe, E. Z.,
(8) West, P. W., Sen, B., 2. Anal. Chem. 153, 177 (1956).
DONALD R. EKBERQ ELAINEC. SILVER Biosciences Operation Missile and Space Division General Electric Co. King of Prussia, Pa. WORKsu ported by NASA under Contract NA82-1538
Quantitative Analysis of Mixtures of Isomeric Aminobenzoic Acids by Gravimetry SIR: Although the qualitative s e p aration of the isomeric aminobenzoic acids has been reported (3, 4), no quantitative results have been published. This paper describes the quantitative analysis of mixtures of o- and m-, mand p-, and o-, m-, and p-aminobenzoic acids using bromination, chelation, and gravimetric methods.
zinc chelate of o-aminobenzoic acid was anal zed according to the procedure of &merman and Selzer ( I ) whereas the mother li uor was analyzed according to Methoa A. RESULTS AND DISCUSSION
benzoic acid as determined by bromination. The second method (Method B) was developed to not only check the accuracy of the first method but also to permit the analysis of mixtures of 0-, .m-, and paminobenzoic acids. 0Aminobenzoic acid was separated from m-aminobenzoic acid by treating the solution with a 50% excess of zinc nitrate solution to form the insoluble zinc chelate of o-aminobenzoic acid at pH 5.5 (2). The chelate was dissolved in 4N hydrochloric acid and analyzed as well as the mother liquor, containing m-aminobenzoic acid, by titration with a standard solution of potassium bromide/bromate. Since paminobenzoic acid is converted quantitatively to 2,4,&tribromoaniline, mixtures of m- and p-aminobenzoic acids were analyzed according to the procedure described in Method A. To analyze a mixture of o-, m-, and p-aminobenzoic acid it is necessary to remove the ortho isomer by chelation with zinc ion since both 0- and p-aminobenzoic acids are converted to the same product, 2,4,6-tribromoaniline. The isolated zinc chelate was analyzed according to the procedure of Cimerman
Two methods for the quantitative analysis of mixtures of o- and m-aminobenzoic acids were developed. The EXPERIMENTAL first method (Method A) involved the conversion of both isomers to a triChemicals. The isomeric aminobenzoic acids were purified by recrystalbromoderivative by means of standard lization from water. Isomeric aminopotassium bromide/bromate solution benzoic acid solutions in 4N hydro( I ) , o-Aminobenzoic acid (anthranilic chloric acid were employed at various acid) is converted quantitatively to the concentrations: 1, 2, 5, and 10 grams base insoluble compound 2,4,6tribromoper liter. Standard solutions of potasaniline whereas m-aminobenzoic acid is sium bromide/bromate, sodium thioconverted quantitatively to the base sulfate and zinc nitrate were prepared soluble compound, 2,4,6-tribromo-3from “Baker Analyzed” reagent grade aminobenzoic acid. The mixture was chemicals. (J. T. Baker Chemical Co.) Analytical Procedure. ANALYSIS treated with base to dissolve the acid OF MIXTURESOF 0- AND m-AMINOand the undissolved 2,4,6tribromoBENZOIC ACIDS. METHOD A. A 25-ml. aniline was determined gravimetrically. solution of 0- and m-aminobenzoic acids The solubility of 2,4,6-tribromo-3was brominated by adding a 50% aminobenzoic acid is too great in water excess of a standard solution of 0.1N to permit gravimetric analysis. The potassium bromide/bromate according weight of m-aminobenzoic acid in the to the procedure of Cimerman and mixture w w determined by subtracting Selzer ( I ) . After standing in the dark the weight of o-aminobenzoic acid from for one hour, an excess of potassium the total weight of the isomeric aminoiodide was added and the solution titrated with a standard solution of 0.1N sodium thiosulfate. The mixture containing 2,4.&tribromoaniline and 2,4,6-tribromo-3-aminobenzoic acid was made basic by the addition of 20% Table I. Analysis of Isomeric Aminobenzoic Acid Mixtures. sodium hydroxide. The base insoluble Weight, mg. compound, 2,4,6-tribromoanilineJ was Taken Founda obtained by filtration, dried and weighed. 0mP 0-0 Sd mS Pb METHODB. A 25-ml. solution of 0and m-aminobenzoic acids was treated (40.0) (40.0) ... (39.7)b (0.1) (40.3)* (0.1) . . . with a 50% excess of 0.LV zinc nitrate 40.0 40.0 ... 39.7 0.1 40.2c 0.1 ... 190.0 io.0 ... 189.3 0.3 10.4c 0.2 ... solution at a controlled pH of 5.5 to 10.0 190.0 . . . 9.9 0 I 189.3c 0.2 ... precipitate the zinc chelate of o-amino50.0 50.0 . . . . . 5O.lb 0.1 49.8 benzoic acid (2). The precipitate was 356.3 18.7 . . . 356.1b 0.3 18.6 dissolved in 4147 hydrochloric acid and 5 n ~ . 5n 5.2b 0.2 94.3 . . . ... ... this solution as well as the mother 0.4 29.7 0.3 30.1b 30.1 30.0 30.0 30.0 liquor, containing m-aminobenzoic acid, 0.4 89.7 90.6; 9.9 0.1 90.0 10.0 90.0 was analyzed according to the procedure 44.8 5.1 0.2 45.0 45.2 0.1 45.0 .5.0 of Cimernian and Selzer (I ) . 10.0 89.gb 0.3 90.0 0.4 10.0 90.0 90.0 ANALYSIS OF MIXTURESOF m- AND Average standard deviation 0.2 0.2 ~-AMIKOBENZOIC ACIDS. The solution was analyzed eccording to Method A. Average of triplicate. ANALYSIS OF MIXTURESOF 0-, mb Determined by Method A. Determined b,y Method B. AND P - ~ I I N O B E N Z O I C ACIDS. The solud Standard aeviaticn. tion was treated uith a 50% excess of zinc nitrate sol~ition. The precipitated I . .
0
5
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ANALYTICAL CHEMISTRY
...
... 0.4 0.1 0.2 0.1 0.3 0.1 0.1 0.2
