SOLUBILITY RELATIONS I S GAS-LIQUID SYSTEJIS 11. T H E SOLUBILITY AND RATE OF SOLUTIO?; OF OYYGES I S WATER* BY J. LIVINGSTON R. YORGAN AND H. RIVINGTON PYNE
I. Introduction A new apparatus for determining gas solubilities, and its use in determining the solubility of carbon dioxide in water, have been described in a previous paper, where it was shown that the results obtained are comparable with those obtained by shaking the two phases together. I t was desired to check the results obtained by the apparatus with those obtained by analytical means, and also to determine its availability for use in measuring the rate of solution, for which only tedious methods have so far been worked out. Oxygen was chosen for the experiments, both because of the large number of determinations of its solubility in water which have been made by other investigators by analytical and other methods, and because of its use by hdeney and Becker’ in their very careful work on the rate of solut,ion. By methods involving several days for their determinations, these authors worked out the equation vi = ( 1 0 0 - wi)( ~ - e - ’ ~ ) , where w is the percentage of the saturation value which goes into solution in the t,ime t, and w1 is the percentage already in solution, e is the base of the natural logarithmic system, and b is a constant for the apparatus, dependent upon the absolute temperature, the area of the liquid-gas surface, and the liquid volume. 11. Apparatus The apparatus used has been previously described. The only change made was in the substitution of a new form of burette, that used in the carbon dioxide work not giving sufficiently reproducible results when used with t h e much less soluble oxygen. The new burett’e is shown in Fig. I , and is patterned after the one used by Cady, Elsey and Ber@ in their work on helium. It communicates through a small stopcock with one side of a manometer, the other side of which opens into a bulb which can be cut off from communicat’ion with the atmosphere. When so cut off, fluctuations of atmospheric pressure have no effect on the pressure within the apparatus. The original burette was made as shown in the figure, and with an internal diameter of I mm. for the manometer. The small pocket above the stopcock gave trouble, and the small bore of the manonicter made it inscnsitivr, so a “Contributions from the Chemical Laboratories of Columbia University, S o 6 2 ; . ‘Adeney and Becker: Sei. Proc. Roy. Dublin Soc., 15 in.s.r S o . j I iry18:; KO.44, Sept. (1919); Sept. (1920); Phil. Mag., (6) 38, 317 ( 1 9 1 9 ~39, ; j8j (1920‘;42, 81 (19211. 2 C a d y , Elsey and Berger: J. Am. Chem. SOC., 44, 1456 (19221.
1819
SOLUBILITY RELATIONS IN GAS-LIQUID SYSTEMS
new burette was made, in which a three-way stopcock was placed a t the juncture between manometer and burette, and in which the manometer bore was increased to 6 mm. The capacity of the sniall bulb on the burette was made 3 . 7 5 cc. The straight portions were of 5 mm. diameter, giving a reading error of about 0.1%~less than other errors involved in the determination. 111. Experimental
Oxygen was drawn from an electrolytically prepared supply in a cylinder, and purified by passage through concentrated sulfuric acid, over a heated spiral of copper oxide, through a soda-lime tube, and finally through distilled water a t the temperature of the experiment. Xnalysis of samples of water saturated with oxygm prepared in this iyay failed t o show measurable differences from samples saturated with oxygen drawn directly from the cylinder, so that these precautions were probably unnecessary. The distilled water used in the determinations was freed of dissolved gases by boiling under a reflux condenser in the usual way.
IV. Results The average of nine determinations of the solubility of oxygen in water a t 2 5 ’ gave a value for the Ostwald Solubility Coefficient, I , of 0.0310 *.oooz. For convenience of comparison this value has been recalculated in terms of the Bunsen Coefficient, which has been generally used by those investigators favoring analytical methods. The recalculations have been made by means of the wellknown formulae: b = I > < - 273 273
+t
/
b ’ = b X -P - P
P
where t is the temperature and P the pressure of the experiment, and p is the vapor pressure of the solvent. The results are compared with those of other investigators below:’ The results for the rate of solution of oxygen in water are given in Table I, where t is the time in minutes, w (obs.) is the experimentally determined percentage of the saturation value a t the corresponding time, and w (calc.)
FIG.I
Carlson: Z. angew. Chem., 26, 713 (1913); Bohr and Bock: Ann. Physik (3)44, 138 (1891);Dittmar: “Challenger Expedition, Report on Chemistry andPhysics,” 1, 172 (1884); Winkler: Ber., 24, 3609 (1891);Thresh: J. Chern. SOC.,5 5 , 5 5 2 (1889);Hufner.Ann.Physik, (3) 1, 632 ( 1 8 7 7 ) ; Geffcken: Z. physik. Chem., 49, 268 (1904); Richardson: Unpublished work in this laboratory, using an analytical method.
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J. LIVIXGSTON R. MORGAN A S D H. RIVINGTOS PTNE
is the percentage as calculated from the equation of ddeney and Becker, using the empirically determined value of o.oj2; for the constant b. The results are plotted in Fig. 2. Observer
Morgan and Pyne Carlson Bohr and Bock Dittmar Winkler Thresh Hufner Geffcken Richardson
I
b
o 0310
o 0284 o 02867 o 02904
b' 0 02;;
0 028j;
o 02831
02743 0.02729
0
0
02745
0.0308 0 . 0 3 I I:
ttme in m t n u f e s
FIG 2
Rate of Solution of Oxygen in Water. TABLE
t 2
4 6 8
m (obs.)
9.60 18.8; 2 j .81
w (calc.)
78.91
18.87
81.44
27. IO
88.11
83 . 4 8 88.09
91.08
90.80
39.40
I2
45.36
44.23
I5
53.61 58.28 63.24 68.21 72.19
53 . 3 9 58 .48
17
23 2.5
w(ca1c.j
78.81
10
20
w(obs. j
I O . 00
34.71 40.74
34.44
I
64.j 2 68.jj ;I . 4 8
93.38 95.70 97.02
98.34 99,33 IO0
.oo
92.96 05 I3 96 i 6 97 56 98.65 101.39 '
SOLCBILITY RELATIONS IN GAS-LIQUID SYSTEMS
1821
V. Discussion As with the previous paper, the main interest lies in the agreement of t h e results with those obtained by other methods, in this case mainly analytical, confirming the value of those methods as well as the availability of the method presented here for gases of low as well as for those of high solubility. Of particular interest, perhaps, is the agreement of the values obtained for rate of solution with those calculated from the equation of hdeney and Becker, for this may give us a method for making in a few hours determinations which have previously required days. In this connection it may be noted that a second degree equation, found by the method of least squares, failed t o fit the experimental curve within the experimental error.
VI.
Strmmnrp.
The solubility of oxygen in water a t 2 5 ' has been determined, and t h e result shown to be in agreement with those obtained by other investigators using other methods. The rate of solution of oxygen in water has been determined, and the experimental results have been found to be in conformity with the equation of Adeney and Becker.
