The solubility of sulfur dioxide in 50% (wt./wt.) sulfuric acid was evaluated by regular solution theory, and the results verified by experimental measurements in the temperature range of 25 C to 70 C at pressures of 60 to 200 PSIA. The percent (wt./wt.) of sulfur dioxide in 50% (wt./wt.) sulfuric acid is given by the equation %SO2 = 2.2350 + 0.0903P - 0.00026P 10 to the 2nd power with P in PSIA

Chang, K. K.

Compton, L. E.

Lawson, D. D.

English

NASA Technical Reports Server

52 
SOLUBILITY OF SULFUR DIOXLDE Ly SULFURIC ACID 
ORIGINAL PAGE Karl K. chang, Leslie E. Comptoa and Daniel D. Lawson 
Jet Propulsion Laboratory 
caiifornia ' n s t i t u t e  of Technology 
Pasadena, Cal i forn ia  91103 
OF: POOR QUALITY 
The so lub i l i t y  of su l fu r  dioxide in 50% (wt./wt.) s u l f u r L  a c i d  was evaluated by regular  so lu t ion  
theory, an3 the  r e s u l t s  ve r i f i ed  by experimental measure=nts i n  the temperature rmge  of 25'C  ti^ 72°C 
a t  pressures of 60 t o  200 PSIA. 
is give. by the  equation =SO - 2.2350 + 0.0903P - 0.00026P2 with P in PSIA. The percent (wt./vt.) of su l fu r  dioxide in 50% (wt./wt.) su l fu r i c  acid 2 
LXTRODUCT I O N  
There a r e  f i v e  thermochemical water s p l i t t i n g  cycles that have been extensively invest igated (see 
notes) .  
ranges of 50 t o  60%. 
ambient pressures. 
increased so that:  
They a l l  have in commoa su l fu r  dioxide and a i u i ' k  acid a s  p a r t  of the cycle  In concentration 
Laboratory bench scale units have been assembled and Fn a l l  cases operated a t  
In an): l a rge  scale-up t o  p r a c t i c a l  commercial un i t s  the process pressures  mubt be 
1. 
2. 
Gains in process e f f i c i enc ie s  can be achieved. 
The hydrogen and oxygen can be produced a t  high pressures to  avoid the cos t s  of punpmg. 
00 review of the l i t e r a t u r e  very l i t t l e  da ta  exists 011 the  s o l u b i l i t y  of su l fu r  dioxide In su l fu r i c  acid 
( 1 , 2 , 3 ) .  A l l  of these data  a r e  ac low pressures  of su l fu r  dioxide in su l fu r i c  ac id ,  and the data  given 
by Sbeck  et. al. was shown t o  fo l lov  Xenry's Law (3). 
we have ca lcu la t sd  the s o l u b i l i t y  of su l fu r  dioxide in 50% <wt./wt.) su l fu r i c  acid. To ver i fy  these 
ca lcu la t ions ,  aeasurements of the so lub i l i t y  of the  gas in the  ac id  were undertaken in the  tezpera ture  
range of 25°C to  70°C a t  pressures  of 60 t o  200 P S U .  
Because of the Importance of this information 
HISCIBEITY OF L I Q U I 3  SYSTEX 
In general, so lub i l i t y .  o r  mi sc ib i l i t y  of two l iqufds,  Is t o  be expected I f  there is  a decrease in 
t he  f r e e  energy of mixing, 1.e.. 
Inasmuch a s  the entropy of a i x i u g  S h  is always pos i t ive  (1.e.. - Th- < 0) ,  the  enthalpy of 
mlxing Qx w i l l  v i r t u a l l y  determine so lub i l i t y .  The la t ter  term for non-polar and some polar sub- 
stances is pos i t ive  and its magnitude is proport ional  to the difference of the respect ive s o l u b i l i t y  
parameters, 6 ,  which are the  square roo t s  of the cohesive-energy dens i t ies .  
the 
and 
(2) 
2 
AH& ' (61 - 62) 
Thus. the c lose r  tha eolubilitlr parameters values, the  smaller  w i l l  be and, consequently, - -  
m lx '  grea te r  the  decreaae In AF 
Fsr the  condi t ion of l i qu id  Immiscibility 
Scot t  (4). 
the  f O l l 0 ~ b g  approximation was o b t a b e d  by Hildebrand 
2 V (61 - 62) > 2RT (3) 
PRECEDING PAGE BLANK NOT. FILMED- 
https://ntrs.nasa.gov/search.jsp?R=19830016792 2020-03-21T04:28:51+00:00Z
53 
Material 
H 2 S 0 4  (25°C) 
ORIGINAL PAGE IS 
OF POOR QUALITY 
Solubi l i ty  Molar Volume, V 
Parameter, 6 cct  g-le Remarks 
18.14 53.28 6 calc 'd  from vapor pressure data  ( 5 )  
If an approximation is made for  V by using the arithmatic mean of V1 and V2 when Vl * V2, then the 
(4) 
expression becomes: 
$ (V1 + Vz) (61 - 6 2 ) 2  > 2RT 
23.46 18.069 
If the  quotient Q is greater than 1, then the h i q u a l i t y  of Equation 4 is s a t i s f i e d  and the l i qu ids  are 
immiscible. 
These equations o r  approldmations are t o  be regarded as a f i r s t  order estimation or guide in the 
An estimation of the miscibi l i ty  of su l fu r  dioxide (50% [vt./-wt.)-sulfurl.c acid as per Equation 
determination of miscibi l i ty  of a system and should be experimantally ve r i f i ed  i f  pract ical .  
(5) a t  25'C (298K) is obtained from the results of the calculat ions shown in Equation 6): 
6 ca l c ' d  as above (5) 
2 (20.80 - 13.75) 
(6 1 1/2 (46.79 + 35.67) 3.25 Q =  2 x 1.986 x 298 
Evaluation of terms in Equation 6 is s h a m  in Table I. 
exceeds 1. Therefore sulfur  dioride is not completely mlacible in SO% (vt . /vt/)  su l fu r i c  acid. Fig- 
ure 1 is a photograph of a tvo-phase-liquid system using the 50% H2SO4. 
the calculated value of Q is 2.31. 
centrated su l fu r i c  acid.  
The calculated value of Q in Equation 6 
For concentrated s u l f u r i c  acid 
This result suggests t ha t  su l fu r  dioxide is more soluble In  con- 
Table 1. Values of So lub i l i t y  Parameters and Molar Volumes 
SO2 (25'C) 10.75 46.79 6 ca lc ' d  from Antolne equation 
constants (5) 
Thc volume of the glass  ampule used in tNs axpe rbwl t  vas f i r s t  ca l ib ra t ed  v i t h  lmm amounts of 
water. 
s t i r r i n g  bar. 
mnd t h e  ampule vas sealed. The system vas slowly heated and alloved t o  coma t o  equilibrium a t  each 
measurement temperature. Care was exercised t o  avoid t h e  formation of etDJlsiona. The experimantal 
apparatus is shown i n  F i g u r e  2 .  
Then a knovn quantity of 50% s u l f u r i c  acid vas p-.tc;a Li ';he q u l e  along v i t h  a magnetic 
Sulfur dioxide was subeequaatly condensed i n t o  the ampule a t  l iquid nitrogen temperature, 
A quadratic regression analysis  performed on the  data gava the following equation 
2 SO2 - 2.2350 + 0.0903P - 0.00026P2 
where P is the vapor pressure of sulfur  dioxide from 60 t o  200 psla  (Figure 3) .  
CONCLUSION 
(7) 
The r e su l t s  show that  the sa lub i l l t y  of su l fu r  dioxide In su l fu r i c  = id  deviates from Henry's Law 
a t  higher pressures (Figure 3) ( 3 ) .  
ORIGINAL PAGE IS 
OF POOR QUALiTV 
ACKNOWLXDGMENT 
The research described in  this paper was carr ied out at the Jet Propulsion Laboratory, Cal i fornia  
I n s t i t u t e  of Tecchnologp, and was supported by t he  Department of Energy through an agreement with NASA. 
1.  
2 .  
3. 
4. 
5 .  
NOTES -
The General Atomics Sulfur-Iodine cycle is described by: 
SO2 + 2E20 + I2 + H2SQ4 t 2EI 
H 2 S 0 4  + SO2 + 5 0  + y 1 O2 
2HI + E2 + I2 
Ispra  Mark 16 cycle is coaceptually the same as t he  General Atomic cycle. 
The Westinghouse Hybrid Sulfur ic  acid cycle  is represented by: 
SO2 + E20 + H2S04 + H2 by e lec t ro lys i s  
H 2 S 4  + SO2 + H20 + 3 O2 
The Iapra Mark 11 cycle is conceptually the same as t he  Westinghouse Hybrid cycle. 
A prepresentation of t h e  Ispra Mark 13 Sulfur-Bromide Hybrid cycle  I s  given by the following: 
SO2 + 2H20 + Br2 * H2S04 + 2ffBr 
1. 
2. 
3. 
4. 
5 .  
6 .  
N2S04 + SO2 + E20 + T 1 O2 
2HBr -+ H2 + B r  by e l ec t ro lys i s  2 
REFERENCES 
J.  T. h n n  
“Solubili ty of Sulphurous Oxide in Sulphuric Acid“ 
Cham. News 66 270-272 (1882) 
F. D. Miles and J .  Fenton 
‘”he Solubili ty of Sulfur Dioxide in Sulphuric Acid” 
J. Chm. SOC. p. 59-61 (1920) 
A. Simack, J. Kichalek, 8.  Kadlec and J. Vosolrobe 
”Loslichkeit von Schwef e l d i d d  in Schwef elaiiure” 
Chem-Ing-Tech 1077-8 (1969) 
J. 8 .  Hildebrand and R. L. Scott  
Reinhold Publishing Corp.. New York, N . Y .  (1950) 
S .  Ohe 
Computer Aided Data Book of Vapor Pressure 
Data Book Publishing Co., Tokyo, Japan, Sept. 1976 
J. C. Cjaldbaak 
“The Solubi l i ty  of Nitrogen i n  Organic Liquids” 
Acta. CSem. Scand. 2 127 (1963) 

ORIGINAL PAGE IS 56 F POOR QUALITY 
20.06 1 1  I 1 I I I I 
18.0 - /-z-z-u- 
0" 16.0 - 
- 14.0 - 
m 
I 
- 
N 
z 
s 120- - 
- -- 
,, /--: i5 10.0 - z - 0" 8.0 - m I- f l  
V # 
QL 
w 
E 6.0 - 
Q 4.0 - 
# 
# 
6 O H E N R Y ' S  LAW PREDICTIONS - 
OEXPERIMENTAL DATA 
2.0 - - 
0.0 I 1 1 
TEMPERATURE OF SYSTEM (OC) 
Figure 3. "he so lub i l i ty  of sulfur diogide in (50% wt./wt.) 
in sulfuric acid. 


Solubility of Sulfur Dioxide in Sulfuric Acid

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