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Gas-chromatographic method for determining the solubility of gases in liquids
GAS-CHROMATOGRAPHIC METHOD FOR DETERMINING THE SOLUBILITY OF GASES IN LI QUID S * V. G. BEREZKIN, V. S. KRUGLIKOVA a n d V. YE. SHIRYAYEVA U.S.S.R. Academy of Scionces (Received 24 November 1970)
DETERMINING the solubility constant of oxygen in organic compounds is an important technical problem. To solve this problem gas-chromatographic methods, as well as conventional statistical methods, have been used in recent years. Well known gas-chromatographic methods of determining distribution constants may be conventionally separated into two groups. I n one group the gas chromatography is used as an analytical method to determine dissolved gases liberated from high boiling solvents. In the second group the distribution constant is determined directly from chromatographic retention values. The latter well developed group of methods is based on a conventional relationship between retention volume and distribution coefficient [2, 3]. It was found experimentally, that in the range of low concentrations, the distribution coefficient is constant and for polar compounds is independent of the amount of stationary liquid phase, the type and flow rate of carrier gas, the type of solid carrier and column length [4]. Porter [5] determined the solubility of paraffin, cyclic hydrocarbons and alcohols in di-isodecylphthalate for the first time by gas-liquid chromatography. The methods involved the use of a solvent as stationary liquid phase in the chromatographic column and the dissolved material was added by a pulse method in the carrier gas flow. Subsequently [6] the same authors determined the solubility of chlorine and nitrosyl chloride in Cle-C20 paraffinic hydrocarbons at a temperature somewhat higher than the melting point of solvents. The method assumes the use of a pure solvent, the dissolved material may be purified in a preliminary column. The accuracy of solubility measurement by this method is considerably affected by solvent volatility. The authors of another study [4] proposed to use for volatile solvents hermetically closed columns joined to the system by injection needles to enable them to be disconnected easily from the device and less of solvent determined by weighing. The distribution constants of acetylene hydrocarbons in N,Ndimethylformamide obtained by this method agree with data obtained by the statistical method. * Neftekhimiya 12, No. 1, 130-135, 1972. 26
The solubility of gases in liquids
27
When this method is used for determining the solubility of polar materials in apolar solvents the possible adsorption on the surface of the solid carrier involves a considerable error in measurement. The use as solid carrier of glass spheres is restricted by the small proportion of stationary liquid phase retained on them. Kvantes and Reinders [7] used thin steel spirals, c a which up to 20-25% solvent (of the weight of filler) is retained. A comparative estimate was made in one of the papers [8] of the effect of solid carrier on solubility: diatomite, glass and wire spirals were studied. The coefficient of distribution of i-C4Hlo in ethyleellosolve at 20 ° in glass was 27.85, on wire spirals 27.7, on diatomite 26.9 and 27-5 using the statistical method. An advantage of the pulse method is the possibility of determining solubility in a ternary system, if the third component continuously enters the carrier-gas flow. Urd0rtunately, the use of this method to determine solubility of oxygen is inadvisable as the method is insufficiently accurate for determining solubility of light gases slightly soluble in liquids. I n this case chromatography is used for the analysis of gases liberated from solutions. I f the solvent has a low boiling point, the solution is fed by pulse method into the chromatographic column, where the dissolved gases and solvent are separated. The solubilities of oxygen and nitrogen were thus determined in several organo-silicon compounds [9]. To liberate gases from aqueous and petroleum solutions prelimirm~ compartments were used arranged before the separating column. I n one of the studies [10] a petroleum specimen saturated with oxygen was placed in a cell heated to 75 ° and the dissolved gases expelled by carrier gas flow and passed into the chromatographic colunm. Swinnerton [11] proposed to use a special cell for the liberation of dissolved gases from water, by which gases (02, N2, CI-I4, CO and CO2) contained in the solution of a concentration 0.3 × 10 -~ % were determined. Several authors [11-15] used a similar method for expelling gases from the specimen to determine O2 and H2 contained in water and in electrolyte solutions. The accuracy of determining solubility was ± 3 %. Data indicate t h a t gas chromatography is a rapid and fairly accurate method of determining gas solubility. A shortcoming which complicates the extensive use of this method is the need to add an accurate amount of liquid previously saturated with gases. Manipulation in air with this sample requires special precaution because of the possible contamination of the sample with oxygen. I n one of the papers [16] in addition to the analytical part of the apparatus a description is given of the use of a circulatory system for the saturation of the liquid with gas. This facilitates the experiment and gives more reliable results; however, the systems still remain very complex. The chromatographic method of determining solubility of oxygen in liquids proposed in this study is distinguished by the fact that the liquid is saturated with air directly in the unit where the sample is introduced.
28
V. G. BEREZKIN et al.
Air and not oxygen was used for saturation. This is more convenient from systematic point of view since it is difficult to obtain pure oxygen and the use of oxygen increases the probability of oxidation. The apparatus used in this study consists of a chromatograph in which the gases dissolved in the liquid sample are analysed, a special attachment, in which the liquid sample is saturated with air, followed by the discharge of the dissolved gas by helium (carrier-gas). f
)--
L
5
D
Ac~/~vd 8/~#ha I charcoal gel i
%!
I,,
II--b-'
I
i
I
.
I [
I
.1
B FIG. 1. Layout of the apparatus used for chromatographic determination of the solubility of gases in liquids: /--thermostatically controlled attachment; a--two-way tap, b--bubbler; 2--katharorneter; 3--fractionating column; 4--recording device; 5--instrument measuring the velocity of the carrier-gas; 6--six-way tap; 7--three-way tap; 8--driers.
The general layout of the apparatus is shown in Fig. 1. Since this paper is concerned with the solubility of oxygen, it was necessary to separate oxygen and nitrogen chromatographically. The gases were analysed in a KhV-1 chromatograph with a heat conductivity detector; analytical columns 2 m in length, 4 m m in diameter were filled with molecular sieves 5A (0.25-0.4 mm fraction). The temperature of the fractionating column was 55 °, the velocity of the carrier-gas (helium) 50 ml/min. A typical chromatographic curve of the separation of dissolved gases is shown in Fig. 2. As shown by the layout, a thermostatically controlled attachment is joined to the chromatograph through several taps. The system used for saturation of the liquid sample with oxygen should satisfy the following main requirements: 1) rapid and complete saturation with gas of the sample studied
The solubility of gases in liquids
29
by bubbling; 2) measurement and control of sample volume during saturation; 3) complete elimination of gas used for saturation from all parts. The system developed by the authors satisfies all these requirements. The thermostatically controlled attachment is a U-shaped glass tube calibrated in paa't ABC. A liquid sample of about 2 ml is filled into this part. Both bends of the tube above the levels of the sample are joined with a two-way tap, which directs the gas flow either through the liquid or the upper joint. Saturation of the sample with oxygen and passage of the carrier-gas are carried out in the right, widened part of the tube, a porous plate being soldered in the base. With the position of taps shown in Fig. 1 the carrier-gas enters the chromatograph and the air, tap a being closed, presses out the liquid from the tube into bubbler c. Numerous experiments show that passage for 2 to 3 min produces saturation of the sample with gas. mV
N2
rrlm 2
600 ~-
~00
200
I
mln 5
I
I
I
14 3
2
FIG. 2
1
0
o
I
o.o5
o.~o oz m'l'
Fro. 3
FIG. 2. Chromatographic curve showing the separation of oxygen and nitrogen. FZG. 3. Dependence of the peak area on the volume of oxygen added.
After saturation with a turn of tap 7 both ends of the tube are joined to the atmosphere and the liquid is lowered from the bubbler into volume ABC. Using a six-way tap, helium is directed into the attachment and the carrier-gas is passed into the space above the liquid. By turning the two-way tap helium is directed through the liquid and the dissolved oxygen is expelled and enters the chromatograph. To collect liquid vapour carried off with the carrier-gas during passage through the liquid sample, an additional column
~ ' . G . B E R E Z K I N et al.
30
containing silica gel (50×0.4 cm) is incorporated before the fractionating column. The amount of oxygen is determined from the areas of chromatographic peaks; prior to this the apparatus was calibrated absolutely for oxygen. TABLE
1.
R E P R O D U C I B I L I T Y OF
S O L U B I L I T I E S OF
OXYGEN IN
ORGANIC COMPOUNDS
Solubility of oxygen, ml O2/1. Boiling this method results in point, I the literature °C exp. 1 exp. 2 iexp. 3 average o~ deviation [17, 18] !
Compound
n-Hexadeeano p-Xyleno Nitrobenzene
287.0 138.4 209.0
34"8 27"0 15"4
34-8 26.4 15.0
33.6 27.8 15-2
34"4 27'1 15"2
2.2 2.5 1.3
32"8 29'1 15"4
T h e d e p e n d e n c e of t h e p e a k a r e a on t h e v o l u m e of gas i n t r o d u c e d is s h o w n in Fig. 3. A c o m p a r a t i v e e v a l u a t i o n of this m e t h o d was m a d e using m a t e r i a l s w i t h solubility c o n s t a n t s k n o w n f r o m t h e l i t e r a t u r e . T a b l e 1 indicates t h a t t h e m e t h o d p r o p o s e d enables fairly a c c u r a t e solubility c o n s t a n t s to be obtained, t h e r e l a t i v e e r r o r of d e t e r m i n a t i o n being 2 - 3 % . I n this s t u d y t h e solubility of o x y g e n was m e a s u r e d in Cs-CI6 paraffins, CI-Cs alcohols a n d some a r o m a t i c h y d r o c a r b o n s ; solubility c o n s t a n t s o b t a i n e d are s h o w n in T a b l e 2. T A B L E 2. S O L U B I L I T Y OF O X Y G E N I N ORGANIC COMPOUNDS AT 3 0 °
Compound
Boiling point," °C
n-Paraffins octane
-
l~onane
decarle
undecane dodecano trideeane tetradecane
125.6 150.8 174.0 195.0 216.0 234.0 252.0
pentadecano
270.0
ml 0,/1.
propound
hoxadeeane 34'2 n -alcohols 34"5 methyl 41 "3 ethyl 40"9 propyl 36'6 butyl 36"8 amyl hexyl 35-0 heptyl octyl 32"0
Boiling point, °C
ml Odl.
287'0
28.7
64"7 78'2 97"2 117"0 137'0 157"0 175"0 194"5
Compound
Aromatic hydrocarbons 22'2 benzene 27.9 toluene 31.0 p-xylene 31.3 C15-C16 31-6 fraction 31.8 synthol 29.7 C17-Cls 26.1
Boiling point, °C
ml O~/1.
80.4 110.6 138.0 100-123/ / 2 mmHg 123-146/ /2 m m H g
33.3 39.2 36-8 33.0 29.9
W h e n s t u d y i n g n u m e r o u s p r o b l e m s such as, for e x a m p l e , liquid p h a s e oxidation, d e t e r m i n a t i o n of t h e solubility of o x y g e n a t increased t e m p e r a t u r e s is i m p o r t a n t : As a result of t h e use of a t h e r m o s t a t i c a l l y controlled a t t a c h m e n t ,
The solubility of gases in liquids
31
t h e solubility of o x y g e n was d e t e r m i n e d in m a n y c o m p o t m d s a t t e m p e r a t u r e s r a n g i n g f r o m 30 to 150 ° (Table 3). _din increase in t h e s a t u r a t i o n t e m p e r a t u r e m a y i n v o l v e a d d i t i o n a l errors of d e t e r m i n a t i o n due to higher v o l a t i l i t y of the liquid studied. T h e use of a c a l i b r a t e d c o n t a i n e r in t h e a t t a c h m e n t , which helps to m e a s u r e liquid v o l u m e a f t e r s a t u r a t i o n , p r a c t i c a l l y eliminates this ource of error. T A B L E 3. S O L U B I L I T Y OF OXYGElq Ilq ORGAlqIC C0MPOUlqDS AT D I F F E R E N T T]~MPERATU'RES
Boiling point, °C
Compound
n-Decane
Toluene Hcxanol
i
174"0 110.6 157'0
Solubility of oxygen (ml O=/1.) at. differont t empora15uros, °C
30-0
50-5
70"6
93'0
154.2
41.3 39.2 31.8
40'3 37"6 29"4
36-1 24-5 27.1
35"0 21"0 22"9
10.7
I t should be n o t e d t h a t a t increased t e m p e r a t u r e o x i d a t i o n m a y t a k e place in parallel w i t h s a t u r a t i o n . T h e p r o p o s e d a t t a c h m e n t design facilitates t h e chemical r e a c t i o n u n d e r a n a l y t i c a l conditions. F o r this purpose, t h e liquid s a t u r a t e d w i t h o x y g e n was r e t a i n e d in t h e a t t a c h m e n t for v a r y i n g lengths of time, t h e a m o u n t of o x y g e n dissolved being t h e n d e t e r m i n e d . R e s u l t s j u s t i f y t h e e x t e n s i v e use of t h e m e t h o d p r o p o s e d for d e t e r m i n i n g solubility. SUMMARY
A simple g a s - c h r o m a t o g r a p h i c m e t h o d was d e v e l o p e d for d e t e r m i n i n g t h e solubility of o x y g e n a n d o t h e r light gases in organic liquids in a wide r a n g e of t e m p e r a t u r e (30-150°). T h e m e t h o d is highly sensitive a n d can be used to d e t e r m i n e t h e solubility c o n s t a n t s a n d a b s o r p t i o n kinetics of chemically a c t i v e gases. REFERENCES
1. V. M. OLIVSKII and I. F. (~OLUBEV, Tr. GIAP 6, 45, 1956 2. A. T. JAMES and A. J. P. MARTIN, Biochem. J. 50, 679, 1952 3. G. J. PIEROTTI, C. H. DEAL, E. L. DERR and P. E. PORTER, J. Amer. Chem. Soc. 78, 2989, 1956 ' 4. G. A. KURKCI:I] and A. V. IOGANSON, Dokl. AN SSSR 145, 1085, 1962 5. P. E. PORTER, C. H. DEAL and T. H. STROSS, J. Amer. Chem. Soc. 78, 2999, 1956 6. M. F. PROKOF'EVA and V. K. BUKINA, Uzb. khim. zh. 1, 40, 1964 7. A. KVANTES and G. REINDERS, Gazovaya khromatografiya, Sb. dokl. na I I Mezhdunar, simpoziume v Amsterdame (Gas Chromatography. Proceedings of the I I International Symposium in Amsterdam). Izd. inostr, lit., Moscow, 1961 8. A. D. ZORIN, A. ¥c. YEZHELEVA and G. G. DEVYATYKH, Zavodsk. lab. 29, 659, 1963 9. Y. M. GORBACHEV and G. V. TRET'YAKOV, Zavodsk. lab. 32, 796, 1966
32
V . G . BEREZKIN et al.
10. P. G. ELSEY, Analyt. Chem. 31,869, 1959 11. J. W. SWINNERTON, V. G. LINNERBOM and C. H. CHEEK, Analyt. Chem. 34, 483, 1962 12. A. A. KILNER and G. A. KATCLIFF, Analyt. Chem. 36, 1615, 1964 13. K. A. GUBBNIS, S. N. CARDEN and R. D. WALKER, J. Gas Chromatogr. 3., 98, 1965 14. J. HALASZ a n d W. SCHNEIDER, Brenndtoff-Chemie 41, 225, 1960 15. V. R. ALISHOYEV, V. G. BEREZKIN and V. P. PAKHOMOV, Zavodsk. lab. 10, 1204, 1966 16. K. E. GIBBNIS, S. N. CARDEN and R. D. WALKER, J. Gas. Chromatogr. 3, 330, 1965 17. Spravoehnik po rastvorimosti (Handbook on Solubility). Edited by V. V. Kafarov, vol. 1, book 1, 1961 18. A. Y. McKEOVCN and R. 1~. HIBBARD, Analyt. Chem. 28, 1490, 1956
DETERMINING the solubility constant of oxygen in organic compounds is an important technical problem. To solve this problem gas-chromatographic methods, as well as conventional statistical methods, have been used in recent years. Well known gas-chromatographic methods of determining distribution constants may be conventionally separated into two groups. I n one group the gas chromatography is used as an analytical method to determine dissolved gases liberated from high boiling solvents. In the second group the distribution constant is determined directly from chromatographic retention values. The latter well developed group of methods is based on a conventional relationship between retention volume and distribution coefficient [2, 3]. It was found experimentally, that in the range of low concentrations, the distribution coefficient is constant and for polar compounds is independent of the amount of stationary liquid phase, the type and flow rate of carrier gas, the type of solid carrier and column length [4]. Porter [5] determined the solubility of paraffin, cyclic hydrocarbons and alcohols in di-isodecylphthalate for the first time by gas-liquid chromatography. The methods involved the use of a solvent as stationary liquid phase in the chromatographic column and the dissolved material was added by a pulse method in the carrier gas flow. Subsequently [6] the same authors determined the solubility of chlorine and nitrosyl chloride in Cle-C20 paraffinic hydrocarbons at a temperature somewhat higher than the melting point of solvents. The method assumes the use of a pure solvent, the dissolved material may be purified in a preliminary column. The accuracy of solubility measurement by this method is considerably affected by solvent volatility. The authors of another study [4] proposed to use for volatile solvents hermetically closed columns joined to the system by injection needles to enable them to be disconnected easily from the device and less of solvent determined by weighing. The distribution constants of acetylene hydrocarbons in N,Ndimethylformamide obtained by this method agree with data obtained by the statistical method. * Neftekhimiya 12, No. 1, 130-135, 1972. 26
The solubility of gases in liquids
27
When this method is used for determining the solubility of polar materials in apolar solvents the possible adsorption on the surface of the solid carrier involves a considerable error in measurement. The use as solid carrier of glass spheres is restricted by the small proportion of stationary liquid phase retained on them. Kvantes and Reinders [7] used thin steel spirals, c a which up to 20-25% solvent (of the weight of filler) is retained. A comparative estimate was made in one of the papers [8] of the effect of solid carrier on solubility: diatomite, glass and wire spirals were studied. The coefficient of distribution of i-C4Hlo in ethyleellosolve at 20 ° in glass was 27.85, on wire spirals 27.7, on diatomite 26.9 and 27-5 using the statistical method. An advantage of the pulse method is the possibility of determining solubility in a ternary system, if the third component continuously enters the carrier-gas flow. Urd0rtunately, the use of this method to determine solubility of oxygen is inadvisable as the method is insufficiently accurate for determining solubility of light gases slightly soluble in liquids. I n this case chromatography is used for the analysis of gases liberated from solutions. I f the solvent has a low boiling point, the solution is fed by pulse method into the chromatographic column, where the dissolved gases and solvent are separated. The solubilities of oxygen and nitrogen were thus determined in several organo-silicon compounds [9]. To liberate gases from aqueous and petroleum solutions prelimirm~ compartments were used arranged before the separating column. I n one of the studies [10] a petroleum specimen saturated with oxygen was placed in a cell heated to 75 ° and the dissolved gases expelled by carrier gas flow and passed into the chromatographic colunm. Swinnerton [11] proposed to use a special cell for the liberation of dissolved gases from water, by which gases (02, N2, CI-I4, CO and CO2) contained in the solution of a concentration 0.3 × 10 -~ % were determined. Several authors [11-15] used a similar method for expelling gases from the specimen to determine O2 and H2 contained in water and in electrolyte solutions. The accuracy of determining solubility was ± 3 %. Data indicate t h a t gas chromatography is a rapid and fairly accurate method of determining gas solubility. A shortcoming which complicates the extensive use of this method is the need to add an accurate amount of liquid previously saturated with gases. Manipulation in air with this sample requires special precaution because of the possible contamination of the sample with oxygen. I n one of the papers [16] in addition to the analytical part of the apparatus a description is given of the use of a circulatory system for the saturation of the liquid with gas. This facilitates the experiment and gives more reliable results; however, the systems still remain very complex. The chromatographic method of determining solubility of oxygen in liquids proposed in this study is distinguished by the fact that the liquid is saturated with air directly in the unit where the sample is introduced.
28
V. G. BEREZKIN et al.
Air and not oxygen was used for saturation. This is more convenient from systematic point of view since it is difficult to obtain pure oxygen and the use of oxygen increases the probability of oxidation. The apparatus used in this study consists of a chromatograph in which the gases dissolved in the liquid sample are analysed, a special attachment, in which the liquid sample is saturated with air, followed by the discharge of the dissolved gas by helium (carrier-gas). f
)--
L
5
D
Ac~/~vd 8/~#ha I charcoal gel i
%!
I,,
II--b-'
I
i
I
.
I [
I
.1
B FIG. 1. Layout of the apparatus used for chromatographic determination of the solubility of gases in liquids: /--thermostatically controlled attachment; a--two-way tap, b--bubbler; 2--katharorneter; 3--fractionating column; 4--recording device; 5--instrument measuring the velocity of the carrier-gas; 6--six-way tap; 7--three-way tap; 8--driers.
The general layout of the apparatus is shown in Fig. 1. Since this paper is concerned with the solubility of oxygen, it was necessary to separate oxygen and nitrogen chromatographically. The gases were analysed in a KhV-1 chromatograph with a heat conductivity detector; analytical columns 2 m in length, 4 m m in diameter were filled with molecular sieves 5A (0.25-0.4 mm fraction). The temperature of the fractionating column was 55 °, the velocity of the carrier-gas (helium) 50 ml/min. A typical chromatographic curve of the separation of dissolved gases is shown in Fig. 2. As shown by the layout, a thermostatically controlled attachment is joined to the chromatograph through several taps. The system used for saturation of the liquid sample with oxygen should satisfy the following main requirements: 1) rapid and complete saturation with gas of the sample studied
The solubility of gases in liquids
29
by bubbling; 2) measurement and control of sample volume during saturation; 3) complete elimination of gas used for saturation from all parts. The system developed by the authors satisfies all these requirements. The thermostatically controlled attachment is a U-shaped glass tube calibrated in paa't ABC. A liquid sample of about 2 ml is filled into this part. Both bends of the tube above the levels of the sample are joined with a two-way tap, which directs the gas flow either through the liquid or the upper joint. Saturation of the sample with oxygen and passage of the carrier-gas are carried out in the right, widened part of the tube, a porous plate being soldered in the base. With the position of taps shown in Fig. 1 the carrier-gas enters the chromatograph and the air, tap a being closed, presses out the liquid from the tube into bubbler c. Numerous experiments show that passage for 2 to 3 min produces saturation of the sample with gas. mV
N2
rrlm 2
600 ~-
~00
200
I
mln 5
I
I
I
14 3
2
FIG. 2
1
0
o
I
o.o5
o.~o oz m'l'
Fro. 3
FIG. 2. Chromatographic curve showing the separation of oxygen and nitrogen. FZG. 3. Dependence of the peak area on the volume of oxygen added.
After saturation with a turn of tap 7 both ends of the tube are joined to the atmosphere and the liquid is lowered from the bubbler into volume ABC. Using a six-way tap, helium is directed into the attachment and the carrier-gas is passed into the space above the liquid. By turning the two-way tap helium is directed through the liquid and the dissolved oxygen is expelled and enters the chromatograph. To collect liquid vapour carried off with the carrier-gas during passage through the liquid sample, an additional column
~ ' . G . B E R E Z K I N et al.
30
containing silica gel (50×0.4 cm) is incorporated before the fractionating column. The amount of oxygen is determined from the areas of chromatographic peaks; prior to this the apparatus was calibrated absolutely for oxygen. TABLE
1.
R E P R O D U C I B I L I T Y OF
S O L U B I L I T I E S OF
OXYGEN IN
ORGANIC COMPOUNDS
Solubility of oxygen, ml O2/1. Boiling this method results in point, I the literature °C exp. 1 exp. 2 iexp. 3 average o~ deviation [17, 18] !
Compound
n-Hexadeeano p-Xyleno Nitrobenzene
287.0 138.4 209.0
34"8 27"0 15"4
34-8 26.4 15.0
33.6 27.8 15-2
34"4 27'1 15"2
2.2 2.5 1.3
32"8 29'1 15"4
T h e d e p e n d e n c e of t h e p e a k a r e a on t h e v o l u m e of gas i n t r o d u c e d is s h o w n in Fig. 3. A c o m p a r a t i v e e v a l u a t i o n of this m e t h o d was m a d e using m a t e r i a l s w i t h solubility c o n s t a n t s k n o w n f r o m t h e l i t e r a t u r e . T a b l e 1 indicates t h a t t h e m e t h o d p r o p o s e d enables fairly a c c u r a t e solubility c o n s t a n t s to be obtained, t h e r e l a t i v e e r r o r of d e t e r m i n a t i o n being 2 - 3 % . I n this s t u d y t h e solubility of o x y g e n was m e a s u r e d in Cs-CI6 paraffins, CI-Cs alcohols a n d some a r o m a t i c h y d r o c a r b o n s ; solubility c o n s t a n t s o b t a i n e d are s h o w n in T a b l e 2. T A B L E 2. S O L U B I L I T Y OF O X Y G E N I N ORGANIC COMPOUNDS AT 3 0 °
Compound
Boiling point," °C
n-Paraffins octane
-
l~onane
decarle
undecane dodecano trideeane tetradecane
125.6 150.8 174.0 195.0 216.0 234.0 252.0
pentadecano
270.0
ml 0,/1.
propound
hoxadeeane 34'2 n -alcohols 34"5 methyl 41 "3 ethyl 40"9 propyl 36'6 butyl 36"8 amyl hexyl 35-0 heptyl octyl 32"0
Boiling point, °C
ml Odl.
287'0
28.7
64"7 78'2 97"2 117"0 137'0 157"0 175"0 194"5
Compound
Aromatic hydrocarbons 22'2 benzene 27.9 toluene 31.0 p-xylene 31.3 C15-C16 31-6 fraction 31.8 synthol 29.7 C17-Cls 26.1
Boiling point, °C
ml O~/1.
80.4 110.6 138.0 100-123/ / 2 mmHg 123-146/ /2 m m H g
33.3 39.2 36-8 33.0 29.9
W h e n s t u d y i n g n u m e r o u s p r o b l e m s such as, for e x a m p l e , liquid p h a s e oxidation, d e t e r m i n a t i o n of t h e solubility of o x y g e n a t increased t e m p e r a t u r e s is i m p o r t a n t : As a result of t h e use of a t h e r m o s t a t i c a l l y controlled a t t a c h m e n t ,
The solubility of gases in liquids
31
t h e solubility of o x y g e n was d e t e r m i n e d in m a n y c o m p o t m d s a t t e m p e r a t u r e s r a n g i n g f r o m 30 to 150 ° (Table 3). _din increase in t h e s a t u r a t i o n t e m p e r a t u r e m a y i n v o l v e a d d i t i o n a l errors of d e t e r m i n a t i o n due to higher v o l a t i l i t y of the liquid studied. T h e use of a c a l i b r a t e d c o n t a i n e r in t h e a t t a c h m e n t , which helps to m e a s u r e liquid v o l u m e a f t e r s a t u r a t i o n , p r a c t i c a l l y eliminates this ource of error. T A B L E 3. S O L U B I L I T Y OF OXYGElq Ilq ORGAlqIC C0MPOUlqDS AT D I F F E R E N T T]~MPERATU'RES
Boiling point, °C
Compound
n-Decane
Toluene Hcxanol
i
174"0 110.6 157'0
Solubility of oxygen (ml O=/1.) at. differont t empora15uros, °C
30-0
50-5
70"6
93'0
154.2
41.3 39.2 31.8
40'3 37"6 29"4
36-1 24-5 27.1
35"0 21"0 22"9
10.7
I t should be n o t e d t h a t a t increased t e m p e r a t u r e o x i d a t i o n m a y t a k e place in parallel w i t h s a t u r a t i o n . T h e p r o p o s e d a t t a c h m e n t design facilitates t h e chemical r e a c t i o n u n d e r a n a l y t i c a l conditions. F o r this purpose, t h e liquid s a t u r a t e d w i t h o x y g e n was r e t a i n e d in t h e a t t a c h m e n t for v a r y i n g lengths of time, t h e a m o u n t of o x y g e n dissolved being t h e n d e t e r m i n e d . R e s u l t s j u s t i f y t h e e x t e n s i v e use of t h e m e t h o d p r o p o s e d for d e t e r m i n i n g solubility. SUMMARY
A simple g a s - c h r o m a t o g r a p h i c m e t h o d was d e v e l o p e d for d e t e r m i n i n g t h e solubility of o x y g e n a n d o t h e r light gases in organic liquids in a wide r a n g e of t e m p e r a t u r e (30-150°). T h e m e t h o d is highly sensitive a n d can be used to d e t e r m i n e t h e solubility c o n s t a n t s a n d a b s o r p t i o n kinetics of chemically a c t i v e gases. REFERENCES
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