F. R., J . Ani. Chem. SOC.79, 1178 (1957). (21) Sloan, J. W., Alexander, B. H., Lohmar, R. L., Wolff, I. A., Rist, C. E., Ibid., 76, 4429 (1954). (22) Snyder, C. F., Isbell, H. S., Holt, N. B., Dryden, M. R., J. Research Nail. Bur. Standards 53, 131 (1954).
(23) Van Cleve, J. W., Schaefer, W. C., Rist, C. E., J . Am. Chem. SOC.78, 4435 (1956). (24) Van Slvke. D. D.. Folch. J.. J . Bid. Chek. 136, 509 (1940): ' RECEIVED for review April 6, 1957. Accepted August 23, 1957. Research supported in part by the Research and D'e-
velopment Division, Office of Surgeon General, Department of the Army. Carried out under the Plasma Volume ExDanders Program of the Subcommittee on &hock, NatiEnal Research Council. -Part of a thesis t o be submitted by J. D. Moyer to the University of Maryland in partial fulfillment of the requirements for the degree of Ph.D.
Analysis of Aromatic Sulfonation Reaction Mixtures WM. H. HOUFF, D. R. CHRISTIE, and R. H. BEAUMONT Research Laboratories, F. C. Huyck & Sons, Kenwood Mills, Rensselaer, N. Y.
b Aromatic sulfonation mixtures containing sulfuric acid and sodium sulfate were analyzed by a three-step procedure. Sulfonic acid was determined b y titration with base of the regenerated sulfonic acid after precipitation of SUIfate with barium hydroxide and passage of the filtrate through a cation exchange resin. Separate determination of total acidity and total sulfate permits calculation of both sulfuric acid and sodium sulfate. In alternative method sulfonic acid, total acid, and total anion are determined to reveal the composition of the reaction mixture. Neither procedure is suitable for aryl sulfonates having an insoluble barium salt nor where anions other than sulfonate, sulfate, or hydroxide are present.
N
methods (1-10, 18, 13) for the determination of sulfonated aromatics have been described, but determination in sulfonation reaction mixtures has remained a problem. Sulfuric acid and sodium sulfate often make a straightforward analysis difficult. During a study of the sulfonation of alkyl benzenes, a rapid method for evaluating the composition of the reaction mixture was required. Because of its ready purification, sodium benzene sulfonate was selected for the preparation of standard reaction mixtures, with the intention of applying the resulting procedure to all types of aromatic sulfonations. The procedure developed is applicable to sulfonation mixtures of numerous aromatics, including some phenols, naphthoquinones, and alkyl benzenes. The sulfonic acids of other aromatic compounds, including naphthalene and dodecylbenzene give insoluble barium salts and so are indeterminable. UMEROUS
BASIS OF METHOD
Wickbold (13) showed that a cation exchange res& could be used for alkalimetric determination of sodium benzene sulfonate. This fact, with the appreciable water solubility of the barium 1866
ANALYTICAL CHEMISTRY
salts of sulfonic acids, suggested the following analytical scheme for sulfonation mixtures containing sodium sulfate (10):
Where no sodium sulfate is present, determination of sulfonic acid and total acid is sufficient. As no tedious gravimetric determination of sulfate is in-
Ar-SOaH
(Ar-SO&Ba
-
1. Ba(OH)2 2. Digestion
BaSOl NaOH Ba(OH12
i
1. Filtration 2. Cation exchange resin
Ar-SOaH Total acidity
Sulfonic acid determined
An alternative, more indirect procedure is possible: Ar-SOsH
-
Standard NaOH
HzSOI
Nazi304 1. Ba(0H) 1 2 . Filtration 3. Cation exchange 4.
Total acid 1. Cation exchange 2. Standard NaOH
Total anion
Standard NaOH
Sulfonic acid determined The results from the three analyses should allow calculation of the reaction mixture composition. The diaryl sulfones frequently found in the sulfonation mixtures of aromatic compounds may be estimated by difference. Aromatic polysulfonations employing high strength oleums or sulfur trioxide may cause formation of considerable sulfonated diaryl sulfone. If the sulfone sulfonic acid has a soluble barium salt, it will cause misinterpretation in the sulfonic acid analysis unless its presence is allowed for. If its barium salt is insoluble in verv dilute hvdrochloric acid, it will interfere with the sulfate determination. Consideration of the initial reagent quantities and of possible sulfonated by-products is important.
volved in the second procedure, it is perhaps preferable. APPARATUS A N D REAGENTS
The only special apparatus required is a 12-inch ion exchange column, I/, inch in inside diameter, preferably fitted with an Ultramax (Du Pont) valve. Domex 50, sulfonated polystyrene resin, Dow Chemical Co., 50-100 mesh. Barium hydroxide solution, 0.2N. Sodium _. hydroxide solution, standard, o*liv* Barium reagent grade* Hydrochloric acid, reagent grade. PROCEDURE
Preparation of Cation Exchange Column. Approximately 5 grams (dry
weight) of 50-100 mesh Dowex 50 resin is introduced into the ion exchange column, washed by the passage of 15 ml. of 4 N hydrochloric acid, then washed with distilled n-ater until t h e effluent is a t p H 4.5 or greater. It is then ready for use. Determination of Sulfonic Acid. A sample of a n aromatic sulfonation mixture containing approximately 3 meq. of sulfonic acid is dissolved in 20 ml. of distilled water and sufficient 0.2K barium hydroxide solution is added t o precipitate all sulfate. After 30-minute digestion on the steam bath, the sample is filtered through a hardened filter paper; the filtrate passes directly into the prepared ion exchange column and the effluent is collected. The precipitate is washed with three 15-ml. portions of distilled n-ater. The last drop of solution emerging from the ion exchange column should h a w a pH of 4.5 or greater. The collected solutions are then titrated with standard 0 . l R sodium hydroxide to the phenolphthalein end point, except that phenolsulfonic acid, because of interference by the slightly acidic hydroxyl group, is titrated potentiometrically to an end point a t pH about 5.5. The quantity of sulfonic acid is calculated. Determination of Total Acidity. An appropriate amount of sulfonation mixture is diluted and titrated n i t h standard sodium hydroxide to a If a phenolphthalein end point. phenolsulfonic acid is being determined, potentiometric titration is preferable. Determination of Total Sulfate. Total sulfate is determined by rapidly (Iddin 50 ml. of 2% barium chloride In d i g i t excess to the hot sample solution. The sample solution is prepared by dissolving a n amount of unknown containing approximately 0.1 gram of sulfate sulfur in 250 ml. of water, followed by 2 ml. of concentrated hydrochloric acid. The precipitated barium sulfate is digested for 30 minutes on a steam bath. Extended digestion should be avoided, to lessen the chance of hydrolyzing the sulfonic acid. The precipitate is filtered through a fine-grained paper, washed with warm water, dried, and ignited to constant weight. Determination of Total Acidity and Total Anion (Alternative Procedure). A sample of aromatic sulfonation mixture is titrated with standard sodium hydroxide, to yield total acidity. After the titrant volume has been reduced by evaporation to approximately 20 ml., it i s passed through a Dowex 50 cationic resin, followed by several portions of distilled water. The effluent may then be titrated with sodium hydroxide, from which the total milliequivalents of anion may be calculated. SENSITIVITY AND REPRODUCIBILITY
The sodium salt of benzenesulfonic acid was twice crystallized from methanol. Three 0.5- to 0.6-gram samples were dissolved in 10 ml. of mater and 10 ml. of 0.2N barium hydroxide was added. This clear solution was passed
through the ion exchange column according to the standard procedure. The effluent was then titrated with a standardized solution of sodium hydroxide. The purity of the sodium benzene sulfonate was found to be 99.7% with a mean deviation of =t0.2%. Using the purified sodium benzene sulfonate, 0.5- to 0.6-gram samples were weighed and diluted n i t h 10 ml. of 0.5N sulfuric acid. After 30 ml. of 0.2N barium hydroxide was added, the samples were digested, filtered, and passed through the ion exchange resin. The amount of sodium benzene sulfonate found was 99.8 to 100.1% of the theoretical. Finally, two stock solutions were prepared by the addition of 5 to 6 grams of sodium benzene sulfonate to 90 ml. of O.50ON sulfuric acid and diluting to 100 ml. From each were drawn three 10-ml. aliquots, which \?-ere analyzed for sulfonic acid, total acid, and total sulfate. By the same procedure a stock solution of sodium p-toluene sulfonate of 96.2% purity was analyzed. The results are summarized in Table I.
barium. The results, which represent three determinations each, are summarized in Table 11. Benzene was sulfonated by known (11) procedures with oleum in the presence of sodium sulfate (Table 111). The principal objective was to estimate the amounts of sulfonic acid and byproduct sulfone formed during the reaction.
Table 111. Benzenesulfonic Acid and Diphenyl Sulfone Found in Sulfonation Mixtures
Sulfonic Acid, 7 0 Sulfone Sulfonating Theoret- Calcd., CI Agent Found ical /o 65%01eum 72.7 73.4 0.3 73.0 73.0 65% oleum 71.5 73.4 1.4 71.1
71.5 100% oleum
The breadth of application embraced by the procedure vias determined by analyzing a number of commercially available aromatic sulfonic acids. I n most cases the sodium salts were used because of greater purity and availability. After sulfonic acid mas determined, synthetic sulfonation mixtures were prepared by adding 5.00 ml. of 0.6002V sulfuric acid to separate samples, principally to determine whether or not sulfonate was occluded when sulfate was precipitated by
86.5
86.1 86.2
97.0
7.4
The composition of the reaction mixture was determined by the alternative procedure for sulfonic acid, total acid, and total anion (Table IV). Samples of sodium benzene sulfonate and sodium p-toluene sulfonate which had been analyzed by the former procedure were used. To weighed samples of the sulfonic acids was added 5.00 ml. of 0.500~2’sulfuric acid.
Table I. Sulfonate, Total Acid, and Total Sulfate in 10-MI. Aliquots of Prepared Mixtures
Sulfonate, Meq. Added Found 1 2.92 2.89 2 2.92 2.92 2.89 3 2.92 IIa 1 3.14 3.15 2 3.14 3.12 3.14 3 3.14 IIIb 1 3.33 3.33 2 3.33 3.31 3 3.33 3.33 Sodium benzene sulfonate. Sodium p-toluene sulfonate. Stock Soln. Ia
0
b
Table
Sample No.
Acid, Meq. Added Found 4.46 4.50 4.49 4.50 4.49 4.50 4.50 4.52 4.50 4.48 4.50 4.48 4.50 4.50 4.50 4.51 4.51 4.50
Sulfate, Meq. Added Found 2.28 2.25 2.25 2.29 2.25 2.27
.. ..
..
2.25 2.25 2.25
2.27 2.24 2.27
..
.. ..
II. Analysis of Commercially Available Sulfonic Acids and Synthetic Mixtures
Sulfonic Acid Derivative Sodium benzene sulfonate Sodium p-toluene sulfonate Sodium p-phenol sulfonate Sodium 2,4-dimethyl benzene sulfonate Sodium 1,2-naphthoquinone-4-sulfonate Dipotassium 2-naphthol-6,8-disulfonate m-Benzenedisulfonic acid Dodecylbenzenesulfonic acid 2-Kaphthalenesulfonic acid 2.50 meq. H2S04 added. * Sample had poor uniformity.
-
Sulfonate,
%
Synthetic Mixture Sulfonate, Total acid,a % meq. 99.6 2.53 95.9 2.51
99.6 96.2 80.2 80.5 89.8 90.1 93.2 93.3 92.0 91.7 91.5-2. 7b Insoluble barium salt Insoluble barium salt
VOL. 29, NO. 12, DECEMBER 1957
2.52
2.51 2:53
1867
CONCLUSION
I n aromatic sulfonation reaction mixtures the quantity of sulfonic acid can be found directly, following removal of sulfate with barium hydroxide and passage of the filtrate through a cation exchange column. The regenerated sulfonic acid is determined alkalimetrically. Sulfate and sulfuric acid may be calculated, folloming determination of total acid and total sulfate. In an alternative procedure sulfonic acid, total acid, and total anion are determined. Because of the lon solubility of their barium salts, some aryl sulfonates are not satisfactorily determined. In the analysis of polysulfonation reaction mixtures the possible presrnce of sulfonated sulfones must he considered. The precision of the sulfonic acid determination is n ithin 1%. LITERATURE CITED
(1) Biffen, F. AI., Snell, F. D., 1x0. EKG. CHEX, X s . 4 ~ ED. . 7, 234 (1935).
Table IV.
Total Acid and Total Anion in Prepared Sulfonation Mixtures
Total Acid, Meq. Total Snion, Xeq. Added Found Added Found 2.50 2.50 5.33 5.35 2.50 2.51 5,44 5.49 2.50 2.51 5.55 5.55 Sodium p-toluene sulfonates 2.50 2.51 5.52 5 57 2.50 2.50 552 5.53 2.50 2.51 5.52 5 56 a Aliquot portions of stock solution. Amount of sulfate would be difference between total anion and sulfonic acid. Sulfonate Added Sodium benzene sulfonate
Epton, S. R., l'rans. Faraday Soc. 44, 226 11948). Hart, R . , I ~ DEKG. . CHEW,Bs.4~. ED. 11, 33 (1939). House, R., Darragh, J. L., .%SAL. CHEM.26, 1492 c1954). Jones, J. H., J . Assoc. O#c. A y r . Chemists 28. 398 11945). Kling, IT.,Puschel, F:, Jlelliand Teztilber. 15, 21 (1934). Marron, T. V., Schifferli, J., ISD. ENG. CHEM.,ANAL. ED. 18, 49 (1946). Shiraeff, D. -1., S m . Dyestuff Reptr. 36, 313 (1947).
(9) I b z d , 37, 411 (1948). (10) Stupel, H I Segesser, A. V., HelL. Chim. Acta 34, 1362 (1951) (11) Swisher, R. D. (to Monsanto Chemical Co.), Brit. Patent 679,826, 679,827 (Sept. 24, 1952). (12) Keiss, F. T., O'Donnell, A . E , Shreve, R. J., Peters, E. D , ANAL. CHEN 27, 198 (1955). (13) Kickbold, R , Z. anal. Chem. 132, 241 (1951).
RECEIVED for revien- May 10, 1 9 5 i . .ICwpted August 12, l95i.
Determination of Oxygen in Niobium W. R. HANSEN and M. W. MALLETT Battelle Memorial Institute, Columbus, Ohio Oxygen in niobium is determined by a diffusion-extraction method using conventional vacuum-fusion equipment. The mean deviation of analyses at the 0.019 weight oxygen level is less than 0.001 weight %. The sensitivity of the analysis could be increased by increasing the sample size.
by fusing the sample in an iron bath, and it seems likely that hydrogen in niobium could be determined by a hotextraction technique. A suitable technique for the determination of oxygen in niobium was developed.
W
Initial experiments were carried out by established vacuum-fusion practice. Specially prepared analytical specimens were dissolved in carbon-saturated metal baths. Analyses \\-ere made in iron and nickel baths a t operating temperatures of 1650" C. (3000' F.) to 1750" C. (3180" F.).
70
ITH the ever-increasing reaiization of the gross effects which interstitials such as oxygen, hydrogen, nitrogen, and carbon can have on the physical properties of metals, considerable effort has been directed toward quantitative determination of these elements. For the most part, adequate methods have been developed fo: the determination of nitrogen and carbon. Probably the most versatile method for determining oxygen and hydrogen in ferrous and nonferrous metals is the vacuum-fusion method, which was originally developed for steels. The physical and thermodj namic properties of the various metals differ so widely that no single vacuum-fusion technique can be applied to all. When niobium and niobium alloys were considered for use in nuclear and other applications a means of determining oxygen and hydrogen n as needed. A brief study showed that hydrogen could be determined readily '
1868
ANALYTICAL CHEMISTRY
EXPERIMENTAL
The results were low and erratic. Varying the temperature of the bath had no effect on the consistency of results. These initial analyses were made with arc melted reference materials which subsequent analyses indicated were not homogeneous. 9 limited number of analyses were made using a platinum bath and an operating temperature of 1900" C. (3460" F.). Although satisfactory material was used, again the results \\ere loiv and erratic. rlng and Wert (1) demonstrated that oxygen could be extracted from niobiumniresheatedat2000"C. (3630°F.) in a vacuum of 10-5 mm. of mercury. This technique was investigated to
determine if it could be used for quantitative analysis. APPARATUS
The vacuum-extraction apparatus ( 2 ) is sensitive to a change of 0.005 nil. a t gas volumes less than 0.5 ml. and a change of 0.01 ml. in the range 0.5 to 2.5 ml. For a 0.3-gram sample, used for most of the determinations, 0.01 ml. of carbon monoxide is equivalent to 0.0023 weight % oxygen. PROCEDURE
Preparation of Samples. T K Oseries of reference samples n-ere prepared : one by arc melting and the other by a manometric technique. High-purity niobium and known amounts of U.S.P.-grade niobium pentoxide were melted together under a helium atmosphere in a tungsten electrode arc furnace. To distribute the oxygen as uniformly as possible. the arcmelted buttons were turned over and remelted twice. Other reference samples n ere prepared by cutting 1.5-inch-long samples from a length of ','*-inch diameter highpurity niobium rod. These pieces nere dry abraded with silicon carbide paper and suspended in a quartz tube by means of a platinum-platinum plus 10% rhodium thermocouple spot-welded to one end. They were heated in the gas
