V O L U M E 19, NO. 1 2
1010 another condensate was determined by phthalization t o be 93.0%. This alcohol fraction contained, in addition to ethanol and water, hexadiene and minor amounts of other compounds. To this fraction was added absolute ethanol, so that the final concentration was 96.1% on the basis of the 93.0% figure. The ethanol content of this mixture obtained by the phthalization method was 95.8%. SUMMARY
The determination of the alcoholic hydroxyl group by esterification with phthalic anhydride was investigated. By modifying the procedure suggested by Sabetay and S a v e s ( I 7 , 1 8 )and standardizing the conditions used, satisfactory results were obtained for a variety of compounds containing alcoholic hydroxyl groups. Phenolic hydroxyl groups do not react with the reagent. Amines react completely or to excess. Using absolute ethanol a precision of 1 t o 2 parts per thousand and an accuracy of 4 to 6 parts per thousand were achieved. I n general, a precision of 2 to 3 parts per thousand and an accuracy of one relative per cent are obtainable. Work with synthetic mixtures and a complex condensate from a vapor-phase catalytic reaction shoir-ed that the presence of water and several types of organic compounds, including aldehydes, does not interfere with the determination of the alcoholic hvdroxyl content. ACKNOWLEDGMENT
The preliminary work on this method was done by the senior author, Edward Shoemaker, and Max Davis. Mrs. Margaret J. Kleinfeld was of great assistance in carrying out the experimental work. LITERATURE CITED
I ) Bryant, W. M. D.. Mitchell, J., and Smith, D. iM., J . Am. C h e m Soc., 62, 1-3 (1940). 12) Christensen. B. E., Pennington, L., and Dimick, P. K.. Txu. ENG.CHEM.,ANAL.ED., 13, 821-3 (1941). 1
Dupont, G., and Dartnon, &I Bull. ., soc. chim., 6, 1208-14 (1939).
Glichitch. L. S., and Naves, Y . R., Chimie & I n d u s t r i e , Special No., 1024-8 (June 1933). Glichitch, L. S., and Naves, Y. R., Parfums France, 11, 216--211 (1933).
Ibid.. 11, 235-41 (1933). Jon& A. W. K., de, Koninkl. Akad. Wetens. Amsterdam, 27. 283-8 (1918): Chem. Zentr., 1922, 11, 948-9. Jong. A. W.K., de, Proc. Acad. Sci. Amsterdam,21,576-8 (19191. Kyriakides. L. P.. J . Am. Chem. Soc., 36, 994-5 (1914). iMeyer, H.. “Analyse und Konstitutionsermittlung organischer Verbindungen,” 6th ed., pp. 362-3, 407-64, Vienna, Juliub
Springer, 1938. Mitchell, H. K., and Williams, R. J., J . Am. Chem. Soc., 60 2723-6 (1938). Ogg, C. L..Porter, W.L., and Willits, C. 0.. ILD.ENG.CHEM A N A L . E O . . 17, 391-7 (1945).
Petersen, J. W., Hedbera, K. W., and Christensen, B. E., I b i d . 15, 225-6 (1943); Christensen, B. E., and Clarke, R. A . . I b i d . , 17, 265 (1945). Kadcliffe, L. G., and Chadderton, E., Perfumery Essent. Oil Record. 17, 254-64, 350-5 (1926) ; quoted in ( 4 ) ,(61,and (6) Raymond, E., and Bauvetier, E., Compt. rend., 209, 439-41 (1939).
Sabetav, S., Ann. chim. anal. chim. appl., 21, 289-90 (1939) Sabetas. S.. ComDt. rend.. 203, 1161-6 (1936). (18) Sabetay, S.,and’Naves, Y . R., Am. chim. anal. chim. a p p i . . 19, 35-8 (1937). (19) I b i d . , 19, 285-9 (1937). (20) Schimmel’s Ber., p. 24 (0ct.-Nov. 1899), and pp. 39-42 (OVI 1912); quoted in (4) and ( 6 ) ; see p. 362 of ( 1 0 ) . (21) Smith, D. M., and Bryant, W. M. D., J . Am. Chem. Soc., 57 61-5 (1935). (22) Stephan, K., J . prakt. Chem., 60, 248-9 (18991. (23) Verley, A., and Bolsing, F., Ber., 34, 3354-8 (1901). (24) Whitmore, F. C., “Organic Chemistry,” pp. 122, 131, 137, New York, D. Van Nostrand Co., 1937. (25) Ibid.. p. 369. (26) Wilson, H. N., and Hughes, W. C., J . Soc. C h m . Zud., 58, 74-i (1939).
RECEIVED December 27, 1946.
Rapid Determination of Moisture in Liquid Sulfur Dioxide B. R. DICAPRIO Culco Chemical Division, American Cyanamid Company, Bound Brook, N . J .
The current phosphorus pentoxide method for analysis of moisture in liquid sulfur dioxide is timeconsuming and involved. A new method, using Karl Fischer reagent and employing a specially developed system to prevent contamination of the sample by moisture, is superior to the phosphorus pentoxide technique for contrnl purposes. This article describes the equipment and technique em-
L
IQUID sulfur dioxide has assumed great importance in the
industrial world. I t is used extensively as a refrigerant, bleaching agent. preservative, and fumigant, in tanning processes, and in the manufacture of other chemicals. The moisture content of liquid sulfur dioxide must be accurately determined, since its presence. even i n ver.y minute quantities, is highly detrimental to metallic equipment. A common analytical procedure callcd the phosphorus pentoside method involves tho weighing of water absorbed on phosphorus pentoxide. Two 3lidvale tubes, each containing a thin layer of asbestos wool on 1 he bottom, are placed in train form and charged with fresh phosphorus pentoxide. The tubes are thrn seasoned, or saturated with dry sulfur dioxide gas, for about 2 hours. .4 tare weight of the tubes is obtained. A known amount of liquid sulfur dioxide is evaporated through the phosphorus pentoxide tubes,
ployed in determining the moisture content of liquid sulfur dioxide by the Karl Fischer method and compares the results obtained by both methods. Emphasis is laid on the necessary precautions, description and use of equipment, method of analytical procedure, and comparative data between the conventional and new methods. Datashow the accuracy and reproducibility of the Karl Fischer method. which are connected in series where water is absorbed a i d weighed. One of the tubes is uscd as a counterpoise in neighing to correct for changcs in atmospheric conditions during the test This method takes several hours t o run and inmlves a special tcchnique for chzrging the Aridvale tubes and connecting them in a rather complicated system employing an air-aspirator, mercury manometer, by-pass valves, special sample cylinder, and sulfuric acid and bubbling tubes, all of which must be maintained and checked periodically.
For control purposes, this method is difficult and tjme-consuming, and in order to keep abreast of production and obtain more accurate results, the Karl Fischer method ( I ) was successfully employed. However, because of the high hygroscopicity of liquid sulfur dioxide, very erratic results were obtained if the proper precautions mere not taken. Moisture absorption in the samplf
.
DECEMBER 1947 A
1011 methanol. R u n up exactly 30 ml. of sample into the dropping funnel and drain into the flask. Remove the flask and replace it immediately with a flask containing Drierite. Titrate the solution of sulfur dioxide and methanol with Karl Fischer reagent in a Karl Fischer buret in the usual manner. Sample Calculation. E = ml. of Karl Fischer reagent for sample F = ml. of Karl Fischer reagent for alcohol blanks D = water equivalent of reagent as grams of water per ml. G = specific gravity of sulfur dioxide a t its boiling point (1.460)
(E - F) X D X 106 = p.p.m. of moisture ml. of sample X G ACCURACY
I n order to determine the accuracy of this technique, known amounts of water were added to samples of sulfur dioxide whose moisture content had been previously determined by the Karl Fischer method. A known amount of water was weighed from s Lunge pipet into 25 ml. of Standardized absolute alcohol, and the liquid sulfur dioxide sample was then added as described above and titrated. Results are given in Table I. A comparison wm made on four samples, and a general a p e + ment of both methods was obtained (Table 11).
Table I. Figure 1.
Sampling and Titrating Apparatuh
uud titrating system waa successfully prevented by the use of the t,echnique and apparatus described below. APPARATUS AND REAGENTS
A 50-ml. calibrated dropping funnel with a center section having a 24/40 ground-glass joint is used t o measure the volume of sample. Three tubes containing indicating grade activated alumina protect the titrating system from access of moisture from the air. A 500-ml. suction flask serves as the sample container. Three 300-ml. Erlenmeyer flasks containing Drierite and, lastly, a Karl Fischer buret which is also provided with tubes of indicating grade activated alumina are also employed. The reagents used are Karl Fischer reagent (standardized, 2) and absolute methyl alcohol (standardized, 3).
Clean and thoroughly dry a 500-ml. suction flask, A , by rinsing with absolute methyl alcohol and drying in an oven a t 110' C. ifter cooling in a desiccator, connect the flask to a line running from the sulfur dioxide cylinder, and draw off approximately 200 ml. of sample. Remove the line from the flask, attach a tube of indicating grade activated alumina, B , t o the side arm, and temporarily itopper the flask. Fit a two-hole rubber stopper into the mouth of a 50-ml. graduated dropping funnel, C. T o one hole, attach a drying tube containing activated alumina, D; to n'lie othcr hole, connect a E-tube t o lead t o a one-hole rubber itopper fitted in the mouth of the sampling bottle. Allow one drm of the tube t o extend t o 0.6 cm. (0.25 inch) from the bottom )f the szmpling bottle. Place a 300-ml. Erlenmeyer flask con1 aining 25 grams of Drierite on the ground-glass dropping-funnel oint, E. Attach a drying tube, F , containing Drierite on the rirck of the dropping funnel. Wrap a piece of cloth, G , around the ,ide arm of the dropping funnel to retain atmospheric moisture that might condense there and thereby introduce water into the titrating flask.
HzO Found by
RIO Added P.p.m. 500 1000
Karl Fiechar" P.p.m. 495 1000 1497
1500 0
T o t a l Karl Fischer value minus blank for water already present.
Table 11. Comparison of Karl Fischer and Phosphorus Pentoxide Values Karl Fischer 78 (check 4 0 (rtwck 2R (rtierk 20 (check
Water Found, P.P.M. values 82)
PnOs values
40) 27) 21)
Table 111. Reproducibility of Method Water Found, P.P.M. '
SAMPLING TECHMQUE
Accuracy of Technique
Sample 1
Sample 2
949 949 (check) 952 (check) 9.52 (check)
203 203 (check) 203 (cherk)
207 (check) 203 (chwk) 203 (check)
9.52 (check) 952 (check)
REPRODUCIBILITY OF METHOD
Six determinations for water content were made on two samplec taken from different cylinders of liquid sulfur dioxide. The reproducibility obtained is directly related to the analyst and equipment used. ACKNOWLEDGMENT
AcknoTTledgment is mlide to W.S. Seaman and H. J . Rodenherger for suggestion of this problem, and to A. G. Hill and associates for helping to prepare this paper.
ANALYTICAL PROCEDURE
Place the thumb over the end of drying tube B on the side arm I F the sampling bottle. The pressure of the sulfur dioxide forces iquid sulfur dioxide up into the measuring tube and into the tiropplng funnel. When 50 ml. hsve collectc,d, release pressure and imrnediatelv drain the stmple from the dropping funnel into the 300-nil. Erlenmeyer flask cJntaining 25 grams of Drierite. rhis will flush out the svstem. Replare the 300-nil. Erlenmeyer mth a dry Erlenmeyer flask containing 25 nil. o f standardized
LITERATURE CITED (1) Fidcher, Karl. Angew. Chem., 48,394-6 (1935). (2) S e a m a n , TT., Norton, A . R.. a n d S l a s s a d , E. A , , IXD. ENG.CHEM., . ~ S . \ L , E n , , 16,517-19 (1914). (3) S m i t h , D. 11..Bryant, IT. M .D., a n d Mitchell, J., J. A m . Chem. SOC.,61, 2407-12 (1939).
RECEIVED February 27, 1947.
