T H E SUPERSATURATION OF GASES I N WATER AND CERTAIN ORGANIC LIQUIDS’ BY JOHN METSCHL~
’
All previous work regarding the supersaturation of gases in liquids may be summarized in a few references. The earliest experiments concerning the evolution of gas bubbles were probably made by O e r ~ t e d . ~Later C. F. Schoenbein4 published an accurate account concerning the supersaturation of gases in aqueous solutions and advanced some rational explanations as to the cause of the evolution of gas bubbles. The term “Supersaturated” as applied to gases in water was no doubt first used by D. Gernea5. The action of solid bodies upon supersatmuratedgaseous solutions was investigated in a qualitative way by Charles Tomlinson,B F. C. Henrici’ and H. Schr3der.s The latter also observed that a sharp and sudden blow upon the walls of the vessel containing the supersaturated solution was apt to cause an evolution of gas due to the momentary decrease of pressure. According t o V. R o t h r n ~ n d Cagniard-Latour’O ,~ had at an earlier date found the same to be true, and in addition noted that vibratory sounds caused the formation of bubbles of gas in supersaturated solutions. Very little has been done in a quantitative way in respect to gaseous supersaturation. Practically the only investigations in this field were made in recent years by A. Findlay” and his co-workers who studied the rate of evolution of carbon dioxide from supersaturated solutions under the influence of colloids and suspensions. The object of the present investigation was ( I ) to construct an apparatus by means of which various gases could be dissolved in water and organic liquids under pressures ranging from one to five atmospheres, (2) to saturate these liquids with gas at a pressure higher than one atmosphere, then reduce 1 Contribution from the Laboratories of General Chemistry of the University of Wisconsin. 2The work included in this paper is from the thesis presented by John Metschl in partial fulfilment of the requirements for the degree of Doctor of Philosophy a t the University of Wisconsin. The subject of this research was suggested by Professor James H. Walton and the investigation was conducted under his direction. 3Oersted: Gehlen’s J. Chem. und Physik, 1, 27 (1806). Schoenhein: Pogg. Ann., 40, 382 (1837). Gernez: Compt. rend., 68, 883 (1866). 6Charles Tomlinson: Phil. Mag., [4] 34, 136, 229 (1867): 45, 276 (1873). F. C. Henriri: Pogg. Ann., 147, 555 (1872). 8 H. Schroder: Pogg. Ann., 137, 76 (1869); Erganzungsband 5, 87 (1871). V. Rothmund: “Loslichkeit und Loslichkeitsbeeinfluessung,” 13 (1907). lo Cagniard-Latour: Ann. chim. phys., (11) 56, 252 (1834). l 1 A. Findlay and G. King: J. Chem. SOC., 103, 1170- (1913); 105, 1297 (1914); A. Findlay and 0. R. Howell: J. Chem. SOC.,121, 1046 (1922).
418
JOHN METSCHL
the gas above them to atmospheric pressure and by shaking out and measuring the volume of the gas which remained in the liquids in a supersaturated condition, determine the amount of supersaturation for the various pressures.
Apparatus The apparatus shown in Fig, I was designed for the purpose of saturating the liquids a t various pressures. This apgaratus was rendered gas tight only after several months of experimentation. Each valve and connection is an individual problem in itself, consequently the apparatus is described in detail. M is a steel cylinder which formerly had been an oxygen tank such as is used by dentists in connection with the adminstration of nitrous oxide. The
T H E SUPERSATURATION O F GASES
~
419
original valve on the tank was removed and replaced by the connections and valves shown in the drawing. These will presently be described. Into the cylinder goo cc. of purified mercury was placed, the total volume of the tank being about 1400 cc. L is a Crane, quick-opening, high-pressure -steam valve having a bronze body and stem, the latter being fitted with a fiber seat. n is an iron tube of about 5 mm. diametw which passes through the mercury at N and comes within 5 mm. of the bottom of the steel flask M . This tube ends a t its upper part in the iron bushing J, where it communicates with the valves E and-H by means of an iron “T”. The valves E and H are remodeled? high-pressure steam valves having cast steel bodies and mild steel stems fitting into cast iron seats. One of these valves is shown in section in Fig. 2.
U
Fro. 2 Tube Valve Scale 4/10
F is an iron cap screwed upon a pipe of the same metal. G is an open manometer composed of sections of barometer tubing. At its lower end the manometer is held in place in the cup of the valve E by means of marine glue.’ The total height of the manometer was about I O meters. The mercury column was read by means of meter sticks fastened along side the barometer tubing; the tubing and sticks all being mounted upon a board which extended the entire length of the manometer. CD is semi-flexible, seamless, copper tubing having an internal diameter of about 1.5 mm. It serves to connect the cylinder M with the carbon dioxide tank B. P is an S-shaped tube of steel such as is used in liquid air apparatus. Its internal diameter is 2.5 mm. It is attached to the inside of the cup of the valve H by means of marine glue and to the iron cylinder R by means of a threaded end. Q is a graduated Pyrex combustion tube102 cm. in length with walls 3 mm. thick and a bore of 13 mm. The tube was held in place in the cylinders R and E1 by means of marine glue. A condensing jacket, not shown in the drawing, surrounded the tube. Water from a thermostat was circulated through this jacket by means of a centrifugal pump so that the temperature of the tube was the same as that of the pressure flask h. 1 The “marine glue” used in this investigation was of the kind employed for waterproofing the canvas in canoe bottoms.
420
JOHN METSCHL
I , 11,I l l , I V and V are needle valves, the “needle” or stems of which were tapered and which fitted into conical seats. Their construction is shown in detail in Fig. 3 . As mercury was apt to come in contact with valve II the latter had all parts made of steel. Valve V was subjected to the action of liquids and gases; to eliminate corrosion it had a monel stem and a brass body. The rest of the valves had brass bodies and steel stems. The tubing between RI and valve 11 was also steel, while the connections between the rest of the valves were of seamless copper tubing having an internal diameter of about 1.5 mm. The whole system of valves, together with the tube Q and the cups R and R1was screwed to a wooden support as shown. Connection between valve I V and the socket P P was made by means of semi-flexible brass tubing having an internal diameter of z mm. The tubing was bent in the form of a spiral and had a total length of about 1.5 meters. Tubing in this form and of this length readily permitted the pressure flask h to be shaken in a horizontal position by means of a suitable shaking device. Liquids to be supersaturated were placed in the flask h which had a capacFRONT S E C T I O N SIOE: ity of approximately 140 cc., and which was made of well annealed glass with a FIG.3 Needle Valve Scale 4/7 very smooth internal surface. Flasks of this kind may be obtained from dealers in scientific apparatus in whose catalogues they are described as “pressure flasks.” The flasks used in these experiments had a threaded brass cap fitted to the neck, the cap being held to the glass by means of a low-melting alloy the composition of which is given’ in George H. Woollatt’s “Laboratory Arts.” The alloy is made by melting together: Bi. . . . . . . . . . . . . . . .40parts P b . . . . . . . . . . . . . . . .zo ) 7 S n . . . . . . . . . . . . . . . . IO I ’ Cd . . . . . . . . . . . . . . . .I O ” Hg . . . . . . . . . . . . . . . . I j )’ Fig. 4 shows the manner in which the brass cap was attached to the neck of the pressure flask, while Fig. j shows the flask screwed into its socket. T is a glass drying tube about a meter in length containing PzO6 and loose glass wool. I‘‘A Teacher’s Handbook,” 139 (1918).
T H E SUPERSATURATION OF GASES
FIG.4 Pressure Flask with Cap Scale 5/6
FIG.5 Pressure Flask with Socket Scale 2/3
42 f
422
.JOHN METSCHL
S is a glass tube containing glass wool, its purpose being to remove the particles of PzOb which might be carried along by the gas as it passes through T. m is a U-tube filled with small lumps of pumice-stone saturated with concentrated sulphuric acid. The purpose of this tube was to remove the greater part of the water from the gas before the latter entered the tube containing the phosphorous pentoxide. g is a two-way stop-cock. W is a wash bottle containing concentrated sulphuric acid. X is a trap to prevent large amounts of water from entering the drying apparatus from the pneumatic trough 2. C1 is a burette used to measure the volume of gas shaken out of the supersaturated liquids. d is a leveling tube. The burette and leveling tube contained mercury over which the gas was collected. The source of the gas used was attached at V . All metal joints from which gas was apt to leak were soldered, while unions of glass to glass, and glass to metal were made tight by the use of marine glue.
Determination of Supersaturation In making a supersaturation determination the procedure was as follows: The valves L, 111,I V , and V were closed, while E , H , I and 11 were open. The valve upon the carbon dioxide cylinder B was then slightly opened by turning the handle A . Carbon dioxide now entered the cylinder M through D. The pressure of the carbon dioxide above the surface of the mercury N caused some of the latter to ascend the iron tube n and enter the iron “T” where the column of mercury divided, one portion ascending the open manometer G, while the other portion entered the pressure tube Q through the iron tube P. As soon as the mercury had filled about 5 cm. of the tube Q the pressure from the carbon dioxide tank was shut off by closing the valve A . Since the manometer G, and the tube e were open to the atmosphere the levels of the mercury in G and Q were the same. When the levels of the mercury in the tubes G and Q had become equal, the valve H was closed. A “Hyvac” oil-pump was now attached to e and the space above the mercury in Q exhausted. The evacuation usually was carried on for about half an hour. During the evacuation the valve 111 was frequently opened and closed so as to admit some of the gas from the gas jar U into the system, the object being to sweep out any foreign gas from the tubes and valves. To be reasonably certain of removing foreign gas from the tubes and valves it was customary to pass some of the gas to be experimented with, through the system by attaching the gas generator at 0 and passing gas through for about an hour before the tube Q was evacuated. This procedure was, however, only resorted to when the gases were changed during the course of the investigation.
THE SUPERSATURATION OF GASES
423
The next step was to close valve I and transfer the connection of the oil pump from e to a. The pressure flask h containing the desired liquid was then screwed into its socket PP. The attached flask was now placed into a can of hot water, and the oil pump started, the valve V being open, but I V being closed as before. The purpose of this part of the procedure was to boil the liquid in the flask h under reduced pressure so as to remove gases dissolved in it. After ebullition had gone on in this manner for ten to fifteen minutes, the valve V was closed and the connection of the oil pump detached from a. The pressure flask was then placed into the horizontal shaking device in the thermostat and its contents allowed to assume the temperature of the bath which was z s 0 C . in all cases. Valve I1 was next closed, and valves IT! and 111 opened, valves I and V being closed as before. Gas now entered from U into the pressure flask H which was shaken in order to saturate the liquid contained therein at atmospheric pressure. As the gas entered the pressure flask the water rose in the gas jar U . In order that the liquid in the pressure flask be saturated with the gas at atmospheric pressure the water levels in U and Z were kept the same during the absorption process. After the absorption of gas by the liquid contained in h had ceased, valves IT and H were opened. The gas in the whole system was now under the prevailing atmospheric pressure, and the mercury levels in G and Q were the same. These levels were recorded as was also the barometric pressure. After this valve 111 was closed. All was now in readiness for the saturation of the liquid in h under pressure. This was accomplished by slightly opening the valve A on the carbon dioxide cylinder B, whereupon the mercury in G and Q began to ascend. As the mercury rose in Q it compressed the gas above it and forced some of it into the liquid contained in the pressure flask. Throughout this procedure the pressure flask was vigorously shaken in the thermostat, and water froin the latter was caused to flow through the glass jacket surrounding the pressure tube Q. When the desired pressure had been attained, the valve A was closed and the shaking of the flask continued until there was no further change in the mercury levels in the tubes G and Q. These levels were then recorded. Obviously the difference in level between G and Q gave the pressure upon the surface of the liquid in h. The absolute pressure in h was obtained by adding the barometric pressure to the above difference in level. The shaking of the flask was next stopped and the valve I V closed. The end of the tube a was inserted into a small vessel of water to a depth of about 2 mm. and the valve V opened. The gas above the liquid in h now escaped. When it ceased to come off, as could be ascertained when no more bubbles were formed in the water from the tube a, connection was made by means of a thick-walled, short piece of rubber tubing of small diameter with the tube b. The shaker was again started and the gas which was in the liquid of the flask h in a supersaturated condition was shaken out and its volume determined in the burette Cl.
424
JOHN METSCHL
Since the total volume of the flask h was known it was easy to find the volume of the liquid which had been previously boiled under reduced pressure and then saturated with gas at the higher pressure. It was only necessary to fill up the flask from a burette with the same kind of liquid which had been used in the experiment, and subtract the volume added from the total volume of the flask. From this and the foregoing data the amount of Supersaturation per unit volume of the liquid could be ascertained. To make the next supersaturation determination with the same kind of gas was comparatively simple. The valve L was opened for a short time so that some of the carbon dioxide in the cylinder M escaped. This caused the mercury in the tubes G and Q to descend and when the valve I I I was opened, gas from U was drawn into the system. Ry suitable manipulation of the valves a wide range of pressure can be brought to bear upon the liquid in the pressure flask. The only limits to the amount of pressure which can be applied are the strength of the various components of the apparatus and the pressure in the carbon dioxide cylinder itself. Following is an example of how the data for each determination were recorded : Method of recording Data Date. April, 18th, 1923. Temp. Room. 27'. 5 C. Gas used. Nitrogen. Liquid used. Ethyl alcohol, 98% by wt,. Vapor press. 68 mm. C2H50Ha t 27'. 5C. f
'
Total vol. of press. flask (h) cc. C2HhOH added to flask after experiment
139.44 cc. at 25OC.
'I
f
42.20
9 7 . 2 4 cc. C2H50Hused in cxp.
Manometer (G) read. at end of exp. Manometer read at start of exp. No. of mm. of Hg on Manometer
1513 mm.
Tube ( Q ) read. at start of exp. Tube read. at end of exp. No. of mm. of Hg on tube
768 mm. 148 mm. -
No. of mm. of Hg on Manometer No. of mm. of Hg on Tube No. of mm. of Hg on Liquid Barometric pressure Absolute press. on Liquid
1415 620 -
98 mm.
__
1415
620
795 = p 741 mm. -
1536 mm.
'THE SUPERSATURATION OF GASES
Burette (CJ read. a t end of exp. Burette read at start of exp. Vol. of gas shaken out
Vol. of gas per
425
r6.90 cc. 0.80 -
16. I O cc.
16. I O cc. of C2H60H= -X IOO
6 . 5 5 ~ a~t . 768 mm. and 27'. 5 C. Vol. of gas per IOO cc. of C2HbOHat 760mm. and 0°C. = 1 3 . 3 1 ~= ~V. IOO
=1
97.24
V / P = -13'31-o.01674. 795 The letters h, G , Q and C1in the above table refer to the corresponding lett,ers in Fig. I with which the apparatus in question is denoted. Experimental The Supersaturation of Oxygen in Water The supersaturation of oxygen in water had previously been observed by A. H. Gill' and C. A. Seyler2. It was thought of interest to investigate the supersaturation of oxygen in water and other liquids to a greater extent with the apparatus previously described. The oxygen used was of the kind which can be obtained in a compressed state in steel cylinders. It had been made by the Linde process and was about 97% pure. However, some determinations were made also with oxygen obtained by dropping distilled water upon sodium peroxide. No difference could be observed in the oxygen from these two sources in the course of the determinations. Conductivity water was used in these experiments.
TABLE I Supersaturation of Oxygen in Water
98.23 94.74
Vol.02 Shaken out cc. 0.88
Vol.On/
I .25
1.32
25.0
.90
IOOCC.
H20 0.90
t°C.
24.5
97.25
I
.95
24.0
98.20 97 98.64 97.84 97.99
2.70
2.75
25.5
4.35 5.90 7.95
4.45
25.0 23.0 23.0
IO. I5
98.12
11.33
water.
I
5.98 8.13 10.35
20.0
Ab:. V01.0~ Press. Std. Cond. Man. mm. P cc. =v P ' mm.
0.78 1.14 I .69
224
337.
7.14 9.09
476 732 1036 1547 2088 2687
10.13
2962
2.38 3.85 5.26
969 1079 1216 1474
I777 2293
2a33
3421
3695 Av .
VIP
0.00347 0.00338 0.00355 0.00325* 0.00372
0.00340 0.00342* 0.00338*
0.00342 0.00344 *Indicates determinations made with oxygen obtained from sodium peroxide and 1 1 , jj
20.0
' A . H. Gill: J. Anal. App. Chem., 6 , No. 1 1 . C. A. Seyler: Chem. News, 67, 87 (1893).
JOHN METSCHL
Winkler, from tables in Landolt-Bornstein. Bohr and Bock, from tables in Landolt-Bornstein. From supersaturation data. The figures in the first column of Table I give the volume of water in the pressure flask h (see Fig. I ) which was saturated wit,h oxygen at the higher pressure. The volume of oxygen shaken out of the water in the pressure flask, after the pressure in the latter had been reduced to atmospheric, is given in the second column. Temperatures at which these volumes were measured in the burette CI (see Fig. I ) are given in the fourth column. In the third column is the volume of oxygen shaken out of I O O cc. of water, at the temperature indicated in column four. The values in column three were obtained from those in columns one and two. The fifth column gives the volumes of column three reduced to standard conditions of temperature and pressure. Pressures indicated by the manometer G (see Fig. I ) are given in the sixth column. These values indicate the pressure at which the liquid in the pressure flask was saturated. Column seven gives the absolute pressure at which the liquid in the pressure flask was saturated, that is, these values represent the pressure of the manometer !plus the barometric pressure. The ratio of the values in columns five and six are represented in the eighth column. The, values in columns five and six were plotted t o form the oxygen-water graph shown in Fig. 6. Sz5 represents the volume of gas absorbed in IOO cc. of liquid at 25OC., and 760 mm. according to the given observer. This value represents the Bunsen absorption coefficient multiplied by one FIG.6 hundred. Supersaturation of Oxygen in Water ~ 2 represents 5 the volume of gas shaken and Organic Liquids out of the supersaturated gaseous solution at 2 s0C.,when the pressure upon the solution had been reduced from 760 mm. to atmospheric pressure. The value for s25 was obtained by plotting the data of columns five and six upon larger sized co-ordinate paper than shown in Fig. 6, and reading off the volume of gas shaken out which corresponded to a pressure of 760 mm. It must, however, be remembered that the value s 2 6 gives the volume of gas shaken out when the absolute pressure above the solution really amounted to two atmospheres, but when the pressure was
THE SUPERSATURATION O F GASES
427
reduced to one half of this amount the volume indicated by 825 could be shaken out, while the gas dissolved at one atmosphere remained in solution. The graph in Fig. 6 shows that the volume of oxygen shaken out of IOO cc. of w a t e r - o r the supersaturation- is approximately proportional to the pressure at which the water was saturated. With greater refinements of measurements and more careful methods of manipulation it is probably that the above supersaturation measurements could be used for determining the solubility of some gases in liquids at higher pressures. Supersaturated solutions of oxygen in water appear to possess conriderable stability. When the experiments in this connection were first begun it was thought that the pressure above the water had to be released very gradually so as not to disturb the metastable solution below. Consequently the gas was released so that all above the solution came off in 15-20 minutes. This method was inconvenient and consumed a good deal of time. Determinations were then made in which the valve upon the pressure flark was opened wide so that all of the gas escaped in a few seconds. No apparent differences in the final results could be detected when the supersaturated solution was shaken to measure the volume of oxygen given off. Only at the higher pressures indicated in Table I, in some cases could a few bubbles be observed rising out of the water when the pressure was suddenly released. But this was the exception rather than the rule. Effervescence was in no instance observed. Neither did the gas appear to come off spontaneously from the water after the pressure above it had been released. This could be shown in the following manner : When the desired pressure in the flask had been obtained, the connection from valve V (Fig. I ) was inserted for a distance of about 2 mm. in water previously saturated with oxygen. Then valve V was quickly opened to its fullest extent allowing the gas above the water in the flask to come out with a rush. A period of quiet ensued. No bubbles formed at the end of the connection in the water indicating that very little, if any gas, was coming from the surface of the supersaturated solution. Even after an interval of 5-10 minutes no bubble formation could be noticed. To borrow a phrase used by Findlayl supersaturated solutions of oxygen in water probably have a considerable (‘period of quiescence”. No doubt, if the pressure had been increased sufficiently the period of quiescence could have been reduced, but it was not convenient to investigate this farther a t the time. The relative stability of the supersaturated oxygen in water solution could be shown in a still more striking way. The pressure flask containing the metastable solution could be unscrewed from its socket without exercising extraordinary care with regard to the sensitiveness of the solution. The bottom of the flask could be bumped against the table, or the sides could be rapped with a block of wood but as long as the surface of the liquid remained 1
Findlay: loc. cit
428
JOHN METSCHL
unbroken no bubbles of gas could be seen to be evolved out of the solution. Only upon shaking the flask so as to break the surface of the liquid could numerous fine bubbles of gas be caused to rise out of the solution, but as soon as the shaking stopped the bubble formation also soon ceased. The shaking had to be continuous and prolonged if all the supersaturated gas was to be obtained from the water. The length of time during which the oxygen remained in contact with the water while under pressure apparently did not influence the results. In the earlier experiments all solutions were kept in contact with the oxygen for fifteen minutes before the pressure was released. Later the same results were obtained when the solution was shaken as soon as the manonieter showed that equilibrium was established, which was two minutes a t the most. Neither were any differences detected after the solution was allowed to stand in contact with the gas for an hour.
The Supersaturation of Oxygen in Carbon Tetrachloride As far as could be ascertained no experiments have been made using organic liquids as solvents in the study of gaseous supersaturation. Accordingly this phase of the problem was investigated to a limited extent. The carbon tetrachloride used was obtained from L. B. Parsons of this laboratory who employed the same kind in his study of the reactions between dry reagents. It was of the C. P. variety and had been allowed t o stand three months in contact with sticks of potassium hydroxide before distillation. The oxygen used was of the kind which is sold compressed in steel cylinders.
TABLE I1 Supersutwation of Oxygen in Carbon Tetrachloride 1'01. CCI, CC.
Vol.02 Shaken out cc.
Vol.Oz/ I O 0 cc. CC14
96.44 98.44 95.79 96.04 94.84 9.1 54 97.24 95.29 96.64 95.64
5.95 18.60 29.50 29.70 41 .oo 41.40 44.10 48.80 6 6 . IO 96.80
6.17 18.89 30.79 30.92 43.23 44.25 45.35 51.21 68.39
'
101.20
t,"C.
24.5 24 .o 24.5 26 .o 24.0 21
.o
23 .o 23 . o 20.0 26.5
Press. Ab?. Vol.0, P St,d.Cond. Man. mm. mm. cc. =v P
4.68 14.39 23.34 23.36 32.93 34.92 35.38 39.95 54.66 74.63
168 488 757 7 83 I 160 1217
1232 I375 1792 2489
VIP
o .0278 0.0295 0.0308 0.0298 0 , 02S4
906 1226 1495 I530 1898 I939 I979
0.0287 o .0287 0.0291
2122
2534 3224
Av ,
0.0305 0.0300 o .0283
no data available for 2 5 O C . 8 2 5 = 2 2 . 5 from supersaturation data. Szb =
The data from columns five and six were used in plotting the graph shown in Fig. 6.
THE SUPERSATURATION OF GASES
42 9
All values for the corrections for vapor tension which were applied for the reduction of the gas volumes to standard conditions were taken from the tables in Landolt and Bornstein. Because of the large volume of gas which was shaken out of the carbon tetrachloride a t the higher pressures it was impractical to make more determinations at more elevated pressures since the burette in which the gas was measured proved to be too small. By using approximabely half the volume of carbon tetrachloride than had been used as shown in the data of column one, the ratio V/P dropped t o values ranging between 0 . 0 2 19 and 0 . 0 2 58. This seems to indicate that some relation exists between the volume of solvent and the amount of gas it can retain when the system is supersaturated. This phase was not farther investigated.
The Supersaturation of. Oxygen in Ethyl Alcohol The alcohol used had been treated with metallic sodium previous to distillation. It had a specific gravity of 0.7992 at I~OC., which .corresponds to about 98y0 ethyl alcohol by weight. The oxygen was from the same source as in the preceding experiments.
TABLE 111 Supersaturation of Oxygen in Ethyl Alcohol Vol. Alc. cc.
97.94 96.99 95.89 95.94 96.84 97.84 95.99
Vol.02 Shaken out cc.
Vol.Or/ 100 cc. Ale.
13.80
14.09 21.34 38.58 53.16 54.62 78.73 82.40
20.70
37.00 51.00
52.90
77.00 79.10
t"C.
26.0 27.0 27.0 27.0
26.0 26.0 26.0
V01.0~ Press. Std. Cond. Man. mm. cc. = v P
11.54 17.29 31.26 43.08 44.74 64.49 67.99
464 691 1267 1644 1738 2476 2654
Abs. P' mm.
\', P
1209 1434
0.0249 0.0256 0.0247 0.0262 0.0257 0.0260 o .0256
2010
2387 2483 3221 3404
Av.
EL4= 1 9 . 9 4 for 9 9 . 7 % alcohol at
24OC. Timofejew:
0.0255
Z.physik. Chem., 6,
151
(1 890). s25
= 1 9 . 5 from
supersaturation data.
The data in columns five and six were plotted to obtain the alcoholoxygen graph in Fig. 6.
The Supersaturation of Oxygen in Acetone The acetone used was of t.he C. P. variety and stood over anhydrous copper sulphate two weeks before it was distilled. The oxygen was obtained from the same source as in the previous experiments.
JOHN METSCHL
430
TABLE IV Supersaturation of Oxygen in Acetone Vol. Acet. cc.
Vol.02 Shaken out cc.
88.94 94.64 94' 79 94.62 94.44 92.29
13.80 24.90 44.80 64.70 87.40
S25= 525
IOO.OO
Vol.Oz/ IOO cc. Acet.
t"C.
15.51
22.5
26.31 47.26 68.38 92.54 108.30
24.5 23.5 24.0
Ab:. P
Vol.02 Press. Std. Cond. Man. mm. P cc. =v
10.38 16.86 30.85 43.24 56.44 65.30
25.5
26.0
398 676 1164 1579 2097 2364
V/.P
mm. 1 I49
I427 1914 23 18 2836 3102
0.0261 0.0249 0.0265 0.0274 0.0269 0.0276 Av. 0.0266
19.48Levi: Gam. chim. ital., 31, 11, 513 (1901). From supersaturation data..
= 2 0 ,o
It should be mentioned that determinations made at the higher pressures, particularly the one at 2364 mm., that the oxygen came out of the supersaturated solution at an appreciable rate as soon as the pressure upon it was released. At the above mentioned pressure the gas came off at the rate of 4 cc. per minute without shaking the pressure flask. The Supersaturation of Nitrogen in Water Nitrogen was obtained by a method used by Just' in his solubility determinations. Conductivity water was used as in the case of the experiments with oxygen and water.
TABLE V Supersaturation o f Nitrogen in Water Vol.H 20 cc.
92.64 96.74 92.64 98.54 96.74 96 74 97.84 92.61 '
Vol.N2 Shaken outcc. 1.20
1.80 2.00
1.80 3.00 4.20 5.10
6.00
\'ol.Nn/ IOO cc. H20
t"C.
v01.N~ Press. Std. Cond. Man. mm. cc.=v P
Abs. P' mm.
1.10 584 1.59 899 1.84 914 1.58 921 2.69 1489 3.88 1847 4.65 2153 5.54 2800
I325
0.00189
I639 1655 1662 2229 2587 2895 3541
0.00177
1.30 28.0 1.86 26.5 2.16 28.0 1.83 25.0 24.0 3.10 4.34 18.0 5.21 25.5 6.48 27.0
V/P
A V*
.53 Just: loc. cit. S25= I .so Bohr and Bock, from tables in Landolt-Bornstein. sZ5= I .so From supersaturation data. s 2 5=I
1
Just: 2. physik. Chem., 37,342 (1901).
0.00201
0.00171
0.00181 0.00210
0.00216 0.00198 0,00193
431
THE SUPERSATURATION O F GASES
As in the previous experiments the data from the fifth and sixth columns were plotted and the water-nitrogen graph of Fig. 7 was obtained, The values for V / P are not in as good agreement with each other as might be desired. This may be due to the fact that a different valve was used in place of valve V of the former experiments (see Fig. I ) . The new valve had a comparatively large cavity about its seat into which water condensed when the water in the pressure flask was boiled under reduced pressure to remove the air. In the shaking out process the water in the cavity apparently interfered with the movement of the gas through the valve, which may partly account for the somewhat erratic results. Moreover, the last portion of the gas in the supersaturated solution came off very slowly, so that prolonged shaking was necessary to obtain a constant reading upon the FIG.7 burette. Thus insufficient shaking might , Supersaturation of Nitrogen in Water result in a second source of error. and Organic Liquids The Supersaturation of Nitrogen in Ethyl Alcohol The alcohol was of the same kind as was used in the supersaturation of oxygen in alcohol. Nitrogen was obtained in the same manner as mentioned in the preceding experiment.
TABLE VI Supersaturation of Nitrogen in Ethyl Alcohol Vol.Nz/ IOO cc. Alc.
Vol. Alc. cc.
Vol. Nz Shaken out cc.
97 a24 96.34 97.24 97.24 97.24 97.24 96.34
11.72 11.40 13,30 13.80 16.10 16.55 25.20 25.91 31.60 32.49 39.30 40.41 50.20 52.10
t"C.
Vol.N2 Press. Std. Cond. Man. mm. cc. =v P
28.0
28.0
27.5 25.0 27.0 27.5 28.0
9.38 11.03 13.31 21.29
576 642 795 1247
26.25 32.50 41.65
1488 1800 2385
Abs. P' mm. I317
1383 1536 1988
V/P
0.0163 0.0172 0.0167 0.0171
2229
0.0176
2541 3126
0.0181 0.0175
AV. 0.0172 S25=13 . I I Just: loc. cit. 13 .o From supersaturation data.
~ 2 5 =
From the data in Table VI the alcohol-nitrogen graph in Fig. 7 was obtained in a similar manner as were the graphs of the preceding experiments.
432
JOHN METSCHL
At the manometric pressure of 1488 mm. and above, the gas came off a t a noticeable rate without shaking the pressure flask when the pressure upon the supersaturated solution was released. This is similar to the observation made in connection with the supersaturation of oxygen in acetone, already referred to. The nitrogen came out of the supersaturated solution very readily upon shaking. Constant readings upon the burette were rapidly obtained and the last portion of the gas did not seem to be held as tenaciously by the alcohol as was the case of nitrogen in water. In this and the experiments following a new portion of liquid was not always put into the pressure flask for each supersaturation determination as long as the same kind of gas was being investigated. The gas in the supersaturated state was merely shaken out, its volume determined, and the same liquid again used for another determination, but saturation being made a t a higher pressure. It was not, deemed necessary to boil the liquid after each determination to make it gas free as long as it had once been boiled and then saturated with the gas in question. This fact accounts for the similarity in the volumes in the firqt columns of some of the later tables. The Supersaturation of Nitrogen in Benzene Dry benzene was obtained from Dr. L. B. Parsons already mentioned in connection with the supersaturation experiments of oxygen in carbon tetrachloride. Nitrogen was obtained in the manner previously mentioned.
TABLE VI1 Supersaturation of Nitrogen in Benzene VOl.Ce,H6 cc.
Vol.Ns Shaken Out CC.
Vol.N2/ IOO cc. COHO
91. I4 91. I4 9 1 . I4 91.14 9 1 . I4 93.59
8.00 11.90 16.20 22.60 29.90
8.78 13.05
40.20
17.77 24.79 32.81 42.95
t"C
27.0 27.0
27.5 28.0 28.0 29.0
Vol.N2 Press. Std. Cond. Man. mm. cc. =v P
7.72 11.48 15.63 21.71
28.73 37.33
492 688 888 1190 1659 2281
Ab:. P mm.
v/p
1228
1424 1624 1926 2395 3015
Av .
0.0157 o .0167 0.0176 o ,0182 0.0173 0.0164 0.0170
S 2 5 = ~ o . 6 1Just: . loc. cit. s25= 13 .o From supersaturation data.
No reason can be given for the lack of agreement between the solubility and supersaturation measurements as given in the above table. When the pressure on the manometer was I 190 mm. and above the gas came out of the wipersaturated solution at an apprecia.ble rate without shaking the flask. The Supersaturation of Nitrogen in Nitrobenzene The nitrobenzene employed was of the C. P. variety. It had been allowed to stand over calcium chloride about two weeks previous to distillation. The nitrogen was obtained by the same method as in the preceding experiments.
433
THE SUPERSATURATION O F GASES
TABLE VI11 Supersaturationqf Nitrogen in Nitrobenzene Vol. CaHaNOz cc.
v0l.N~ Shaken O u t CC.
97.74 97.74
3.40 4.50
97.74 97.74 97.74
10.30
Vol.N2/ IOOCC.
CsHsNO?
3.48 4.60 10.53 13.71 22.81
13.40 22.30
t"C.
29.5 29.5 29.5 30.0 30.0
Press. Vol.N2 Std. Cond. Man. mm. P cc.=V
3.03 4.01 9.16 11.91 19.88
.4bs. P' mm.
VIP
416 549 1238 1688
1149 1282 1971
2707
3440
2421
Av.
0.00728 0.00730
0.00740 0.00706 0.00734 0.00728
SZ5=5.729.Just: loc. cit. s 2 6 = 5 . 6 From supersaturation data.
The nitrobenzene-nitrogen graph of Fig. 7 was obtained in a similar manner as were the graphs in the previous determinations. When the pressure upon the supersaturated solution was released no evolution of gas was noticeable even at the highest pressures shown in Table VI11 unless the pressure flask was shaken. This is in counterdistinction to the fact observed in the case of nitrogen in benzene.
The Supersaturation of Nitrogen in Aniline The aniline used had been allowed to stand over sticks of potassium hydroxide for two weeks previous to distillation. The nitrogen was prepared in the same way as in the previous determinations.
TABLE IX Supersaturationof Nitrogen in Aniline. Vol. C6HaNH2 cc.
98.69 98.69 98.69 98.69 99.87
Vol.N2 Vol.N*/ Shaken IOO cc. out CC. CeHsNH2
2.40 3.90
7.50 10.70 12.20
2.43 3.95 7.60 10.84 12.35
t"C.
Press. Vol.N2 Std.Cond. h'lan.mm. cc. = v P
29.0
2.12
470
29.0
3.44 6.62 9.60 10.90
822
29.0 25.0 25.0
1523 2344 2613
Abs. P' mm.
VIP
1203 I555 2256
3079 3348
Av.
0.0045I 0,00419 0.00435 0.00410 0.00419 0.00427
S25=2.815. Just: loc. cit. s 2 5 = 3 . 3 From supersaturation data.
The aniline-nitrogen graph of Fig. 7 was obtained in a manner similar to the graphs of the preceding experiments. The supersaturated solution of nitrogen in aniline had to be shaken for a considerable length of time because the gas was tenaciously held by the liquid even at the highest pressures shown in Table IX.
J O H N METSCHL
43 4
The Supersaturationof Air in Water The air was drawn into the pressure apparatus through a tube extending outside t,he building. Conductivity water was used as in the cases of oxygen and nitrogen. TABLE X Supersaturation of Air in Water V0l.H20 cc.
Vol. Air Shaken out CC.
Vol. Air/ ~ o o cof r
2.10 4.60 5.70 6.80
2.15 4.72 5.84 6.91
97.54 97.54 97.54 98.44
t"C.
H20
26.0 25.5 25.0
25.0
Vol. Air Press. A h Std. Cond. Man. mm. 1'' w.=V P mm.
1.85 4.07 5.06 j.98
880 I765 2421 2730
VIP
1622 2507 3163 3472
0.002 I O
0.0023 I
0.00209 0.00219
Av.
0.00212
S25= I .724. Winkler, from tables in Landolt-Bornstein. From supersaturation data. 526 = I .65 The air-water graph of Fig. 8 was
had been done in the previous experiments. The air was tenaciously held by the water and only when the shaking of the supersaturated solution was somewhat prolonged could the last portion
The Supersaturation of Hydrogen in Water The hydrogen was obtained by the 0
500
1000
1500 FIG.
2000
BOO
8
Supersaturation of Air and Hydrogen in Water
by Just.' Conduct'ivity water was used as in the previous experiment.
TABLE XI supersaturation of Hydrogen in Water Vol.HZ0 cc.
91.69 91.69 91.69 91.69 92.16
VOLH~ Yol.HZ/ Shaken IOOCC. out CC. of H20
2.30 3.00 3.40 6.60 7.80
t"C.
2.51
22.0
3.27
21.0
3.71 7.20 8.46
22.0 24.5 25.0
Vol.HZ Std. Cond. cc.=v 2.18 2.87 3.25 6.18 7.24
Press. Abe. hlan. mm. P' P mm.
641 902 1052 1958 2255
= I ,759 Winkler, from tables in Landolt-Bornstein. S2&=I . 8 2 2 . Just: lac. cit. p 2 5 = 2.35. From supersaturation data. 526
Just: loc. cit.
VIP
1375 1636 I786 2692 2989
0.00340 0.00318 0.00309 0.00316 0.00321 Av. 0.00321
43 5
T H E SUPERSATURATION O F GASES
No reason can be assigned for the lack of agreement between the supersaturation and solubility data as shown in Table XI.
The Supersaturation of Carbon Dioxide in Water That supersaturated solutions of carbon dioxide in water occur has been known for a considerable time. Both Liebigl and L. Pratesi2 had observed the supersaturation of carbon dioxide in mineral water. The carbon dioxide used in the following experiments was obtained from marble chips and pure hydrochloric acid.
TABLE XI1 Supersaturation of Carbon Dioxide in Water V0l.Hz0 cc.
VOl.COz Shaken out CC.
VOl.CO*/
9 4 . I9 96.54 94.05 96.79 96.64 94.94 96.54
25.0 36.8 19.9 63.0 60.4 67.8 106.7
26.54 38.11 21.15 65.09 62.50 71.41
IOOCC.
of H20
110.50
t"C.
Vol.COn Press. Std. Cond. Man. mm. cc. = v P
25.0
22.77
420
27.0
32.43 18.32 56.74 53.79 61.15 94.63
502
25.0 24.0 24.5 26.0 26.0
602 879 922 1125 1873
Abs. P' mm.
v/p 0 .OS42
1156 1240 1345 1647 1658 1863 2611
0.0646 0.0304 0.0646 o .os83 0.0544
Av
.
0.0505 0.0541
Szj= 7 5 .go. Bohr and Bock, from tables in Landolt-Bornstein. Szs=75.62. Just: loc. cit. s 2 6 = 40.40. From supersaturation data.
There is no agreement between the supersaturation result and any of the solubility determinations. The low value from the supersaturation data is probably due to the escape of gas from the supersaturated solution as soon as the pressure upon it is released. Findlay and Kinga found that supersaturated solutions of carbon dioxide in water were exceedingly sensitive to slight mechanical shock. As the gas above the solution in the pressure flask was released with a rush, it is possible that a portion of the carbon dioxide came out of the solution as a result. The same investigators mentioned above surmised that if solutions of carbon dioxide were saturated at a higher pressure that there would be no period of quiescence when the pressure is reduced. This seems t o be corroborated in the cases of carbon dioxide in water and ethyl alcohol. Because of the lack of agreement between the solubility measurements and the supersaturation data no graphs are shown for the supersaturation of carbon dioxide in water and ethyl alcohol, Liebig: Ann., 30,4 (1839). Gam. chim. ital., 22, 493 (1892). Findlay and King: J. Chern. SOC., 103, 1170 (1913).
* L. Pratesi:
43 6
JOHN METSCHL
The Supersaturation of Carbon Dioxide in Ethyl Alcohol The same kind of alcohol was used as in the case of the supersaturation of oxygen in ethyl alcohol. The carbon dioxide was obtained by the method already described.
TABLE XI11 Supersaturation of Carbon Dioxide in Ethyl Alcohol Vol. Alc. cc.
96.44 97.94 97.14 97.44 98.94 96.94
Vol.CO2 Vol.C02/ IOOCC. Shaken out cc. of Alc.
18.90 20.00
38.40 62 .50 93 110.30
19.59 20.42 39.53 64. I 4 94.80 113.70
t"C.
25.5 26.0 26.0 26.0 22.0
26.0
Vol.CO2 Press. Std. Cond. Mammm. cc. =v P
16.12 16.65 32.24 52.31 79.75 92.73
Abs.
P'
mm.
916 964 1009
0.124 0.096 0 . I45 0.196
112.5
0.208
I275
0.174 0.157
875
130 I74 222
267 384 533
Av.
The values of the ratio V/P are very erratic. If R graph be drawn from the values in columns five and six of Table XI11 the points are scattered to such an extent that it is impossible to draw a representative line bet+een them, hence the value for ~ 2 cannot 5 be determined. The Relation of Supersaturation to Solubility The graphs shown in the foregoing experiments show that the supersaturation i s approximately proportional to the pressure at which the saturation of the gas in the liquid took place. Moreover, if the solubility of a given gas in a given liquid, as used in this investigation, be calculated for different pressures by means of Henry's law, and the solubility so obtained be plotted against the pressure, the resulting graph will be practically identical with the one obtained for the same gas and liquid in which the volume of gas shaken out at atmospheric pressure-the supersaturation-iP plotted against the pressure a t which saturation took place. In the case of carbon dioxide in water and alcohol this statement does not apply. The rate of evolution of gases from supersaturated solutions is of considerable importance in connection with industrial and biological problems as has already been pointea out, by Findlay and King.' This part of the problem will be further investigated. Summary I . An apparatus for saturating gases in water and various organic liquids at pressures ranging from one to five atmospheres is described. This apparatus may also be used for determining the solubility of gases in liquids at different pressures.
Findlay and King: lor. cit.
THE SUPERSATURATION OF GASES
43 i
2 . Saturated solutions of the following liquids and gases have been prepared at pressures ranging from one to about five at,mospheres: Water, ethyl alcohol, acetone and carbon tetrachloride with oxygen. Water, aniline, nitrobenzene, ethyl alcohol and benzene with nitrogen. Water with air and hydrogen. Water and ethyl alcohol with carbon dioxide. After each liquid had been saturated with gas at the elevated pressure, the pressure above the liquid was reduced to that of the atmosphere and the supersaturated gas which remained in the liquid was shaken out and its volume determined. The ratio of the volume so determined to the pressure at which saturation took place was found to be practically constant for any given gas and liquid. I n the foregoing experiments, then, the supersaturation of the gas in the liquid is proportional to the pressure at which saturation took place. 3 . The graph obtained by plotting the volumes of gas shaken out of z1 supersaturated solution against the pressures at which saturation took place, is nearly identical with the solubility-pressure graph obtained by Henry’s law for the same gas and liquid. In other words, when these liquids are saturated a t a high pressure and the pressure above the liquid is then reduced the total amount of gas corresponding to the difference in solubility between these two pressures remains in the supersaturated condition. Notable exceptions to this rule were found in the case of carbon dioxide in water and ethyl alcohol. 4. The rates with which the gases came out of the supersaturated solutions varied with the gas and liquid used. This will be the subject of further investigation.
Madismi, Wisconsin
