76
INDUSTRIAL AND ENGINEERING CHEMISTRY
the preparation of the mixed indicator and attention is directed to the conditions under which the titration should be carried out, particularly regarding the use of artificial light (using a daylight bulb).
Literature Cited Britton, H. T. S., "Hydrogen Ions," S e w York, D. T a n Nos-
t,rand Co., 1929. Clark, W. M., "Determination of Hydrogen Ions," Baltimore, ITilliams R- Wilkins Co., 1929. Hallstrom, J. d.,Ber., 38, 2288 (1905). Hickman. K. C. D., and Linstead, R. P., J . Cheni. Soc., 121, 2502 (1922).
Horat, L. E . , J . Assoc. Oficiat -4gr. Chem., 20, 264 (1937).
VOL. 10, NO. 2
(6) Johnson, A. H., and G r e e n , J., IND. E m . CHEM.,4 n a l . Ed., 2, 2 (1930). ~7~Kheifetz, D,, Chemisation
Agr,
(v. s, s,
~ , ) 5, ,
3-16 (1936).
I. M., Biochem. Z., 189, 26 (1927). (9) Pierre, W.H., ISD.ENG.CHEM.,-4nal. Ed.,5,229 (1933). J., J . Infectious Diseases, 38,293 (1926). (10) Salle, -4. (11) Smith, E. L., Quart. J. Pharm. Pharmacal., 3, 499 (1930). (12) Smith, J. B., S.Assoc. Oficial A g r . Chem., 18,221-37 (1935). (8) Kdthoff,
RECEIVED Sovember 27, 1937. Presented before the Division of Fertilizer Chemistry a t the 94th Meeting of the American Chemical Society, Rochester, N. Y., September 6 to 10, 1937. Published with the approval of the director, \Vest Virginia Agricultural Experiment Station, as Scientific Paper 194. This study was made possible through a research grant given by the Ammonia Department of E. I. du Pont de Nemours & Company, Wilmington, Del.
Confining Liquids for Gas Analysis Solubility of Common Gases in Acid Sodium Sulfate Solution KENNETH .iKOBE . A N D FRANK II. KENTON Department of Chemical Engineering, University of Washington, Seattle, W-ash.
I
S h PREVIOUS paper ( 1 ) reporting the solubility of carbon dioxide in a nuinher of salt solutions, it was concluded
that an acidified solution of sodium sulfate was the most practical confining liquid for use in technical gas-analysis equipment. The purpose of this investigation has been to determine the solubilities in this recommended solution of the gases and gas mixtures commonly encountered in technical gas analysis.
Physical Properties The solution of sodium sulfate used for this work was prepared by dissolving 200 grams of anhydrous sodium sulfate of analytical grade in 800 grams of distilled water and adding 40 ml. of concentrated (36 S ) sulfuric acid of analytical grade. The solution was carefully boiled under a reflux condenser, cooled slightly. stoppered tightly, and cooled to 2.5" C. Solution for use was drawn from the bottom of the flask n i t h a calibrated pipet. CRYSTALLIZATIOX TEMPERATURE. The teniperatul e a t which crystal formation in the solution occurred was de-
terniined, bo that the lowest temperature for use without concentration change would be known. Sodium sulfate decahydrate was found to crystallize from the solution a t 14.6" C. under conditions of violent shaking. Supersaturation appeared to he present a t this temperature, as a considerahle amount of soft mushy crystals precipitated. These crystals redissolved again between 16" and 18" C., but as equilibrium conditions were difficult to maintain while dissolving the crystals these temperatures tend to be high. The confining liquid cannot be used below about 16" C. without danger of precipitation. I-~PO PRESKRE. R The vapor pressure of the solution was determined by means of an isoteniscope modified to allow complete degassing of the solution without changing the concentration of the solution. The vapor pressure of the 3olution is shown as a function of temperature in Figure 1. The data may be represented by means of the equation log P
9.2675 -
2373 T
~
Solubilities of Single Gases
TEMPERATURE
'C.
FIGURE 1. VAPOR PRESSURE OF CONFIXISC LIQ~ID
The apparatus used for the determination of the solubilities was that used previously (1). Two types of burets were used for this work. A mine-air buret was used for the more soluble gftees, such as carbon dioxide, sulfur dioxide, acetylene, and nitrous oxide. This type of buret is accurate to 0.01 ml. in the range 75 to 100 ml. For the lees soluble gases a 21-ml. Haldane buret was used. This has a calibrated range of 6 ml. accurate t o 0,001 ml.; however, readings were taken only to the nearest 0.01 nil. -4standard pressure compensator was used with the mine-air buret and aG open-end manometer \vas used with the Haldane buret. Both burets were water-jacketed and maintained at 25' C. The technic was the same as previously employed. The partial pressure of the gas in the abPorption bulb \vas maintained at 760 mm., as the vapor pressure of the solution was known. The time of shaking t o reach equilibrium varied considerably between the trvo types of burets. With 100-ml. gas samples 20 t o 30 minutes xere sufficient,,while with the 21-ml. samples 60 t o 90 minutes were required because of the decreased liquid-gas cont,act area. All the gases except carbon monoxide were purchased in cylinders and were of a purity greater than 99 per cent. Carbon monoxide was made by dropping commercial formic acid into warm sulfuric acid and purifying the evolved gas by scrubbing
ANALYTICAL EDITION
FEBRUARY 15. 1938
77
Flue gas is one of the most commonly analyzed gases. Its carbon dioxide has a high solubility while carbon monoxide, oxygen, and nitrogen have low and similar solubilities. A change in the relative concentration of the latter three gases will produce only a negligible effect on the total solubility of the gas, as the solubility is almost entirely dependent on the carbon dioxide concentration. Because of this, varying concentrations of air and carbon dioxide were taken as representative flue-gas samples and their solubilities were determined. The results are shown in Figure 2, from which the solubility of a flue gas sample may be found if the carbon dioxide concentration is known.
5
4
3
2
I
I
I 0 0
~
1
1 1
10
5
PER CENT COJN FIQURE
2.
I 1
I 15
20
TABLE
25
cot
TABLE I. SOLUBILITIES OF GASESIS ACID SODIUM SULFATE SOLUTIOS (Temperature 25' C., partial pressure of gas 760 mm.) Volume of Bunsen Gas Solution Gas Dissolved Coefficientb M1. Ml. Ml./m1. so1n.a
co2 NzO CzHz
CzHd CH4 CzHe HI
co 0 2
NI
9.54 24.54 49.54 49.54 49.54 49,54 49.54 49.54 49.54 49,54 49.54 49.54 49.54 49.54 49.54 99.54 99.54 99.54 49.54 49.54 99.54 99.54
131.2 329.2 13.40 13.40 7.88 7.90 17.01 16.98 1.19 1.19 0.47 0.45 0.54 0.53 0.37 0.72 0.39 0.38 0.44 0.44 0.50 0.48
13.6 0.270
M1,
12, .j 0,247
0.159
0.146
0.343
0.324
0,024
0.022
0.0093
0,0083
0.0108
0.0099
0.0073
0 .0 0 6 i
0 0039
0.0036
0.0089
0.0081
0.0049
0.0045
0 Milliliters of gas a t 25' C., partial pressure of 760 mm., dissolved in 1 ml. of solution a t 25' C. b Milliliters of gas, corrected t o 0' C.. partial pressure of gas 760 mm.. dissolved :n 1 ml. of solution a t 25' C .
The results have been expressed in terms of the milliliters of gas at 25" C. a t a partial pressure of 760 mm. dissolved per milliliter of solution a t 25", and in terms of the Bunsen absorption coefficient (CY)the volume of gas (corrected to 0" and 760 mm.) which, a t the temperature of the experiment, is dissolved in one volume of the solvent when the partial pressure of the gas is 760 mm. The data and results for single gases are given in Table I.
Solubilities of Mixed Gases The solubilities of single gases are of little value in themselves, but give the necessary data from which the solubilities of gas mixtures may be calculated by Henry's law. In order to give a check on such calculations, the solubilities of various gas mixtures were determined, and are given in Table 11.
5
95 CO" 10 ~ i r - 90 CO? 1 4 . 5 O? 6 1 ?;I 79.4 cor 20 Air 80 CHc 40.3 CiHt 39.9 CzHz 1 9 . 8
4ir
with caustic solution. The mixed gases were prepared by the use of the mine-air buret. Definite volumes of the gases measured in the buret were passed into a gas-sampling bulb over mercury and the contents of the bulb were thoroughly mixed by passing them back and forth between the buret and the gas bulb. The solubility of the mixture was determined in the same manner as the pure gases.
so2
Gas Iir
SOLUBILITY OF FLUEC i s
SOLUBILITIES O F
Volume of Solution
%
FLUE GAS
11.
99 54 49 54 49 54 49 54 49 54 49 54 49. 54 49.54 49 54 49.54 49 54 49 54
MIXEDGASES
Gas Dissolved M1. M1 /mZ. soh.' 0 51 0 27 0 0053 0 67 0 0135 0 67 1 17
1.16 1.53 1.54 2.21 2.22 2.80 2.75
Bunsen Coefficientb
0 0049 0 0124
0 0235
0 0215
0.0310
0.0284
0.0447
0.0410
0.05fi
0.0533
0 Milliliters of gas a t 25' C., partial pressure of 760 m m . , dissolved in 1 rnl. of solution a t 25' C. b Milliliters of gas, corrected t o 0' C.. partial pressure of gas 760 m m . , dissolved in 1 ml. of solution a t 25' C.
If the approximate form of Henry's law is used, p = R C , the solubility of gas mixtures may be calculated. The results found for the less soluble gases are very good, as the calculation of the solubility of air shows. Using the values for oxygen and nitrogen in Table I, the solubility of air is calculated to be 0.00525 ml. per ml. of solution, compared to the experimental value 0.0053 ml., which is within the experimental accuracy of the determination. Values calculated for the flue-gas compositions given in Table I1 show wider deviation due to the increased solubility of the carbon dioxide. In general, the more soluble the gas, the greater is its deviation from Henry's law. Thus, the calculated solubility of the hydrocarbon mixture of methane, ethylene, and acetylene is 0.0764 ml. per ml. of solution, compared to the experimental value 0.056 ml. The error is due to the decreased solubility of the acetylene under reduced partial pressure, as acetylene is next below sulfur dioxide in the order of solubility.
Discussion The results given in Tables I and I1 for carbon dioxide, acetylene, and mixed gases are accurate to 0.005 ml. in values for solubility or Bunsen coefficient. For sulfur dioxide, because of the high solubility, results are accurate to 0.5 ml.; for the other gases, an accuracy of 0.001 ml. is attained. A comparison of these results with those of Kobe and Williams (1) for carbon dioxide shows a slight difference in values-O.247 compared to 0.242. This difference is due to difference in the concentration of the solution used and in the amount of sulfuric acid added. The true vapor pressure of the solution was used in this work, whereas previously it was assumed to be that of water.
Literature Cited (1) Kobe, K. A , , and Williams, J. S., ISD. ESG. C H E x f . , A4nal.Ed., 7, 37-8 (1936). RECEII-ED December 10, 1937.
