Correlations of Critical Constants with Parachors ROBERT HERZOG Ethyl Corporation, Baton Rouge, La.
T
HE need for accurate estimates of the critical constants, to cinctly. Gamson and Wataon’s recent paper (a) is not given debe used in conjunction with reduced equations of state, has tailed consideration because it was published after completion of been pointed out by Meissner and Redding (8). The corthe present work. The correlations presented(3)are based entirely relation of vapor pressure and latent heat data (10) likewise inon normal parsffin data, which limit their scope of application, volves critical constants which in most cases must be estimated. In general, the amount of experimental critical data is insufficient CRITICAL TEMPERATURE to meet the demand of useful engineering applications. Hence, there is a real need for reliable methods of estimating critical conTwo between temperature boiling point TB,and parachor [PI were proposed by Lewis (6, stants. 7)* These are Of the ‘me: Several methods of estimating critical constants involve the use of the parachor (I,$, 4,8, U), but most of them are of limited T, = a[P] b; T E c [ P ] d (1) application for predicting the critical constants of a particular To = e log [PI f; T E = g log [PI h (2) substance. The purpose of this study, therefore, was to extend Equations 1 apply to various groups of chemically similar comthe range of application of correlations between parachors and critical constants. Particular pounds having the same number of atoms (e.g., CHJ, CHgBr, emphasis is placed upon quantitative measures of the reliability Varioue existing correlationsof the critical constanti CHaCI, and CHaF might constiof the estimated values in order are examined, and the reliability of estimate is tuteonesuchgroup); Equations to provide fair comparison with evaluated for several of them. Four relations in2 apply to various homologous volving the parachor are developed from which relaexisting correlations. Many of series. The constants a h the existing correlations are not tively accurate critical constants can be estimated, are different for each particular discussed in this paper, since using the normal boiling points and calculated paragroupandeachparticularhomolohfeissner and Redding (8) have chore as auxiliary data. Statistical measures of the gous series. The use of these already analyzed them sucreliability of the estimated constants are presented. correlations is limited to com-
+
+
+
+
. . . ..
TABLE I. CRITICALTEMPERAT~~EI Reliabilitye Groups of Compounds Covered by Equationa Equations Derived by Least (TJTE), Absolute Relative, 0 No. Organic Inorganic , Squaresm n* (2S)d % 3A Satd. & .unsatd. hydrocarbons Paraffinic analogs, such TJTB = 2.501 0.417610g [PI 20 1.629 0,034 2.2 as eilicanea Range: 1.29-1.70 (acyclic and uwubstituted) ............ 3B Aromatics & cyclics (substituted TJTB 3 2.640 0.4634 log [PI 28 1.510 0.082 5.4 & unaubatituted) Range: 1.as-1.66 1.607 3C Subatituted aliphstics containing Inorganic halogen com- Te/Ta 2.602 0.4449 log [PI 26 0.075 4.7 pounds halogen‘ L 8 as functional Range: 1.37-1.78 groups 3D Aliphatic esters. ethers, acetals, Some inorganic oxides TJTB = 2.544 0.4429 log [PI 38 0.036 2.6 1.467 oxides* L 0 compounds such Range: 1,361.64 88 SOn,O2, HzO 3E Aliphatic ketones,aldehydes, car- Some inorganic N com- T ~ T = B 2.301 0.3648 log [PI 23 1.618 0.067 4.4 boxylic acids, & N cornpounds pounds such 88 Nr, Range: 1.41-1.69 NIO, N,Oc 3F Aliphatic alcohols & anhydrides Inorganic “anhydrides” T./TB 1.783 0.1479log [PI 14 1.441 0.033 2.3 such 88 COS,H I Range: 1.41-1.52 * Equations are based almost entirely on organic compounds, for which good values of the parachor can be calculated from atomic and structural constanta. Inorganic compounds to which equations were found to apply are indicated. For compounds falling in two or more groups. aa chloroacetic acid 3C and 3E,the average of values obtained by using equationa for each group is recommended. Compounds not covered by any of listed groups can be handled by the principle of chemical similarity. Reliability of estimate for such compounds is indeterminate and probably poorer than tabulated values. Indicated ranges are for experimental (T,/TB)values used in establishing equations. b = No. of experimental (TJTB) values used in determining equation. Relative reliability (per cent) of an estimated value of (TJTB)is defined as: 100 X 28/(Ts/Ts),which is a measure of the percentage deviation of the value from the least squares line which will not be exceeded in about 96% of cases. (Te/T&, the mean of experimental values. has been tabulated and used to calculate a reliability for the equation. This procedure was followed to give a common basis for cornparison of the reliabilities of the equations. The total range of (TJTB) values covered by the datawed in establishing these equations is 1.29 to 1.78. Calculated values which fall outside of this range will have poorer reliebillties than are determined by the defining equation above. d = [Z(TC/TB calcd. Te/Tsexptl*)* ”*; and 25 ia a measure of accuracy to be erpected in about 95% of OMBE. n-2 e All fluoromethanea and moderately subtituted fluoroethanes (M CsHdFs) can be estimated with greater accuracy from Equation 30. Equation 3C gives reeulta which are about 10% high. Highly substituted fiuoroethsnes (aa QCLF:) are handled with Equation 30.
Equation
-
-
-
-
-
-
*
-
1
998
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLE 11. CHI
c
40.0 9.2
F
25.5 55 69 90
Ha
PARACHOR
ATOMIC A N D STRUCTURAL CON~TANT~ 0 20 Triple bond
15.4
c1 Br I
17.5 40.5
N P Aa Sb
E
+3 Carbonyl in ring
CORRELATION O F MUMFORD AND PHILLIPS (9)
S 13e
50 63
l3 Si Be AI Cr TI Sn
21.6 31
0
RCHaR RCHzX RCHO RCOR,
NOR
NOOR RzSeO
Singlet linkage
f2, .,58
3-membered 4-membered 5-membered 6-membered 7-membered
62
2
38 19 0
Double bond Single bond (duplet) :semipolar double bond
64.5 69 80
ring ring ring ring ring
STRAINCON ST ANTS^ -3 -6 RCHXz RCXa RaCX RzCHX RzCHR RJCR RCOOH ClCOCl =C(COOEt)z RCOOR RCOCl RCONHz ClSOCl ROCOOR RSOzC1 RSOzR ROCOCI ROSOzR RSOOR ROSOzOR ROSOOR NOCI NOaR NOiOR NzP Astdes RSeOOH
-9.6
NOzCl PXa REP PO(0R)s CISeOCI BXs A R X ~ SbXa
12.5 6 3 0.8
-4
-12
-9
-15
cx4
RaC CCl4
+
SClr
SClS
S02Clr
SOCl4
NOCls
NC1
rocis PCI~ Six4 SbCla SnX, CrOzCl
--
Strain constant
303.7 -6
B
297.7 297.8
Corrected) parachor xperimental parachor m-Xylene, CEHI(CH~)I: 8 C’S a x 9.2 10 H’s attached to C’s = 10 X 15.4 3 X 19 3 double bonds 1 6-membered ring 1 X 0.8 =
-
73.6
+
154.0
T, = 1 . 1 1 2 T ~ 131.8 Reliability of T, = 5.4%
67.0 0.8
Value of hydrogen in combination with other elements: .C 15.4 8 15.4 C1 12.8 N 12.6 0 10.0 Br 16.4 b R hydrocarbon radical; X negative group, C1, CN, COOR, OR, Br, multiply strain constant by 1.5. etc.; for X 0
pounds which belong 60 groups or series for which sufficient data are available to determine the constants. Equations can be derived from relations 1 and 2 to estimate T./T~from [PI or log [PI, respectively, for such groups and series. The following simpler equation
- blog
[PI
(6)
For ninety-three compounds (halogen- and sulfur-free), other than aromatics and naphthenes, boiling above 235” K.:
---
0
TJTB = a
(4)
Two of the empirical equations proposed by Meissner and Redding (8) have this form and can be readily tested. The method of least squares was used to obtain the best possible constants for the equations as applied to the particular data available, with the results shown in Equations 5 and 6. The constants so derived differ from those of Meissner and Redding, since these authom based their equations only on the critical data for hydrocarbons. thus assuming that the behavior of the hydrocarbons was representative of all compounds. This assumption is open to some question, and while experimental critical data are available for relatively few compounds besides the hydrocarbons, it appeared desirable to consider all available data in calculating the COIIstants in Equations 5 and 6. For thirty-one compounds boilinr below 235’ K.:
Tc = 1.725T~- 5.7 Reliability of Tc = 12.8%
(Corrected) paraohor 285.4 Experimental parachor 285.1 Table I1 does not appear in its entirety in y i NOTE. readily avajlable text or handbook. A portion is reproduced in Gilman’a &ganic Chemistry An Advanced Treatise”, b u t the atrain constants are not even mentioned although they were used in calculating some of the parachors. This erroi has been called t o the attention of Gilman and Leermakers by George Calingaert and G. W.Thomson, of Ethyl Corporation.
-
values were used. For compounds not covered by Mumford and Phillips constants, such as those of germanium, measured value8 or the atomic constants given by Sugden (12)or Lewis (7) were used. Examples of the use of Mumford and Phillips constante are given in Table 11. Comparison of the equations given in Table I with the Lewia Equations 1 and 2 shows that a considerable extension in range of application has been effected. The six equations are applicable to many times that number of homologous series, chemically similar groups, and miscellaneous compounds, most of which were outside the scope of Lewis’ relations because of the paucity of experimental critical data. However, it must be emphasized that the correlation presented i s subject to the inherent limitations of any empirical relation. Returning to Equations 1 and 2, the parachor can be eliminated from each pair of equations to give a relation of the form:
T, = ~ T Ej
EXAMPLES OF USE OF TABLE I1 Triethylamine, (CzHshN: 8CHzgrou s 0 X 40.0 240.0 3 H’s attacEed to C’s = 3 X 16.4 46.2 I N 1 X 17.5 = 17.5
-
Vol. 36, No. 11
(3)
was found, however, to be of more general application since it required the classification of over 140 compounds into only six groups, as shown in Table I. The six groups of compounds (3A to 3F) are described in Table I together with the derived equations and measures of the reliability of estimated T,/TE values. Parachors as used throughout this paper were calculated from the atomic, structural, and strain constants of Mumford and Phillips (9) shown in Table 11,unless otherwise noted. For some of the “simple” molecules (CO, 02,N2, etc.), where calculated parachors differ appreciably from measured values, the measured
Although the stated TB limit of these equations is 235’ K., the value selected by Meissner and Redding, they actually intersect at 225’ K. There is a similar discrepancy in Meissner and Redding’s own equations which, however, is well within their limits of accuracy. The reliabilities in Table I show that the correlations proposed in this paper are considerably better than those for Equation 6 and slightly better than those for Equation 6. From the definition presented in note (c) to Table I, the “reliabilities” reported here are a measure of the maximum deviation, the average deviation being only about 40% as great in each case. The reason fo3 adopting this more stringent definition of reliability is the paucity and doubtful value of much of the available critical data. The equations proposed by Meissner and Redding for aromatics and naphthenes boiling above 235’ K. and for halogen and sulfur compounds boiling above 235’ K. are more complicated and were not tested. Since the groupings used by Meissner and Redding are, in general, different from those used in this paper, estimates of T,can be independently checked by the two methods. CRITICAL VOLUME
Several relations between the critical volume, Vo,and parachor have been proposed. The simplest is due to Sugden ( I d ) : Vc = [P]/0.78
(7)
and is based on his theoretical interpretation of the parachor. The value of the “constant” (0.78), however, has been found to vary by as much as +30%. A purely empirical relation, having
INDUSTRIAL A N D ENGINEERING CHEMISTRY
November, 1944
a higher degree of accuracy, was proposed by Meissner and Redding:
V , = ( 0 . 3 7 7 [ ~ 1-t 11.0)6/4
(8)
A quantitative measure of the reliability of this equation was not given by the authors, A dimensional analysis of the parachor (I I) results in the equation : [PI = KVc6/4Tc'/' 1
(9)
This relation, with K = 0.41, was first proposed by Ferguson ( I ) , who subsequently (8) offered the following empirical relation which is not consistent with dimensional analysis:
[PI = kVc7/ST.'/'
( 10)
(11)
[PI
(12)
by combining several theoretical and empirical equations which apply strictly only to normal liquids. Since Equation 10 appears to have the most rational basis of all the proposed relations, it was first selected for further investigation. Rewriting Equation 10 in the form
V,
K[Pl1.2/Tco*a
(13)
and empirically separating the available data into two groups, the following results were obtained: 1. For compounds having the functional groups -C = 0, -C N, -COOH and -OH, and one to three additional nonfunctional carbons:
V , = 3.34[P]1*'/Te@** Reliability = 10.0%
(134
(13B)
Reliabilities were determined statistically as in Table I.
+
+
V , = (0.3591[P] 14.00)'*a6 Reliability = 15.7%
(16)
The constants in Equation 16 differ from those in Meissner and Redding's paper since the latter were based only on hydrocarbon data. Inspection of the above results shows that the correlations developed in this paper (Equations 13 and 14) are more reliable than those of the type proposed by Sugden or Meissner and Redding, based on the data available a t present. They also show that Meissner and Redding's correlation (Equation 16) is not appreciably more accurate than the simpler modified Sugden relation (Equation 15). Further investigation of equations of the type:
+ an
(17)
where n varies from 1.0 to 1.25, indicated that the reliability of this type of correlation is not very sensitive to the value of n used.
(14)
The estimation of critical pressures, pc, is generally made by means of equations which include T, and V,. Meissner and Redding proposed : p c = 20.8Tc/(V0
- 8)
(18)
Wohl (13,14) proposed:
p, = 21.8Tc/Vc
(19)
and empirically separating the available data in three groups, the following results were obtained. 1. For aliphatic organic compounds containing two or less carbons in addition to the functional atom or group (e.g., CH,, CsHsOH, CzHaCOOH), and all other compounds having T, < 450 OK.:
The reliability of estimate is usually poorer than for T, or V . alone, Equation 12, involving the parachor and Vo, was proposed by Lautie and has been developed in this paper as a method for estimating Vc. Rearranging Eqwtion 12 into the form
V , = 3.58[P]/pC*J6
gives 8 relation for estimating pc (the empirical groupings and values of c are the same a s for Equations 14A, 14B, and 14C). The reliability of estimate for pr is relatively poor (about 20 to 30%) because of the fourth power involved. This reliability is of the same order as that obtained by other generalized methods for estimating pc, and the relation is useful because of its broad scope. I n an attempt t o obtain a more reliable relation for estimating p,, the following line of attack was tried.
Reliability = 8.1%
(14A)
2. For aliphatic organic compounds containing three or four carbons in addition to the functional atom or group, and all other compounds having T. between 450 and 600' K.: J
(15)
CRITICAL PRESSURE
The reliability of the values of Voestimated from Equations 13A and 13B is relatively high, and is not influenced appreciably by the accuracy of the Tc values used (e.g., an error of 5% in T. will introduce an error of less than 2% in V J . Lautie's relation, Equation 12, was also studied further; rewriting it in the form
V* = C[PI/po@*2S
-
Similarly, assuming that Meissner and Redding's relation had the form Vc = (D [PI E)a.2s,it was found that
Vc = (F[Pl
2. For all other compounds:
V , 2.92[P]'.2/T,@.' Reliability = 6.5%
+
20.09 Reliability = 18.1%
[PI = 0.681V,a~4Tc1~4 0.316V0p0*/4
The reliability of Vc values estimated from Equations 14A, 14B, and 14C is about the same m that of estimates made from Equations 13A and 13B. The latter equations are more useful because experimental values of Tc are more numerous than experimental values of pc, and Tc can be estimated much more accurately than p,. When appropriate data are available, relations 14A, 14B, and 14C can be of service by offering an independent check on values of Vcestimated from 13A and 13B. I n order to make a quantitative comparison between the equations developed above and those of Sugden and of Meissner and Redding, the available data were fitted by the method of least squares to equations of the types proposed by these authors. Assuming Sugden's relation to have the form V , = A [PI B, it was found that
V, = 1.447[P]
Lautie (5) arrived at the equations
-
999
V , = 3.3l[P]/p,O." Reliability = 5.2y0
(1413)
3. For aliphatic organic compounds containing more than four carbons in addition to the functional atom or group, and all other compounds having T, > 600' K. (excluding H20) :
v, = 3.19[P]/pe'.*~ Reliability = 7.5%
(14~)
Pc = (C[PI/Vc)*
I n general (11): At the normal boiling point: Therefore Combining with Equations: Or
(20)
-
log p/p, = m nT,/T p = 1, and T = Tb -logpc = m - n T c / T ~ log pc = - m n(a - b log [PI I logpe a' - b'log [PI (21:
-
+
INDUSTRIAL AND ENGINEERING CHEMISTRY
1000
TABLE 111. CRITICAL PRSSSURE Equation NO. 21A
21B 21c
Equations Derived by Least Groups of Compounds Covered by Equationn Squaresa Satd. & unsatd. hydrocarbons L o g p , = 3.0477 - 0.6528109 [PI Range: 1 . 1 4 0 - 1 . 7 9 2 (acyclic,unsubstituted), excluding methane Aromatics and cyclics, exclud- Log pc 3.8584 - 0.9215 log [PI Range: 1 . 4 5 3 - 1 . 7 8 2 ing biphenyls & condensed ring systems Aliphatic amines, esters, halo- Logp, = 3.4271 - 0.782910g [PI Range: 1 , 4 7 7 - 2 , 0 4 7 gen, & S compounds (excluding CHaF and CSZ); inorganic halogen & S compounds (excluding Fd, and NHa
21D 21E 21F
Aliphatic acids, alcohols, & Log pc = 2.9929 - 0.5718 log [PI . Range: 1 . 6 8 1 - 1 . 8 9 6 anhydrides Logpc = 3.3777 - 0.781010g [PI Aliphatic ethers & ketones Range: 1 . 5 0 7 - 1 . 7 1 6 Log p , = 2.6387 - 0.4627 log [PI Aliphatic nitriles, HCN Range: 1 , 5 0 8 - 1 . 6 7 9
(Log nb
Reliabilityc Abso- Relalute tive, CWb % '
18
pdn 1.503
25
1.622
0.100
26
45
1.664
0.070
18
8
1.746
0.036
8.6
5
1.617
0.024
5.7
4
1.594
0,006
1.4
0.035
8.4
a &4pplication of these equations to compounds not specifically covered in listed groups is accompanied by a decreased reliability of estimate (exact magnitude not predictable). S and n have same significance as in Table I ; (log pc),,,is similar to ( T J T B ) ~ . 0 Reliabilities for p , were calculated from values of 2S and (log pc),,,. Since the plus and minus deviations were unequal (in transposing from logarithms t o natural numbers), the larger deviation was used values were calculated from the to give a more conservative estimate of reliability. The tabulated expression : 100 X [(antilog [2S (log p,),l/antilog [(log pJrnl) - 11
+
Vol. 36, No. 11 highest for the most limited groups. Therefore, the best results should be obtained when a single homologous series or group of chemically similar compounds is fitted b y Equation 21. Where sufficient data are available, this procedure is recommended, but owing to the limited data on p,, the less accurate general relations have greater application. To make a quantitative coniparison, the p c relations proposed by Meissner and Redding and by Wohl were re-examined. Fitting the data for eightynine compounds by least squares to Wohl's equation gave: p , = 21.75T,/Vc Reliability = 18.1%
(22)
Similarly, Meissner and Redding's equation gave: pc = 20.8Tc/(Vc
-
8.00)
(23)
Reliability = 19.1% Except in the case of the paraffin hydrocarbons, relation 23 proposed by Meissner and Redding affords, on the average, no improvement over the simpler relation 22 of Wohl. As compared to Equation 21, inspection of the reliabilities shown in Table I11 shows that Wohl's relation is less reliable than five of the six proposed equations. Wohl's relation, however, has greater scope than Equations 21A to 21F, and hence will prove valuable for application to substances not included in the specific groups listed in Table 111. It should be emphasized that Wohl's relation will probably give poorer reliabilities than are indicated above when experimental values of V , and T, are not available and it is necesPROPOSED RELATIONS sary to use estimated values.
An analysis of data for over a hundred compounds showed that Equation 21 could be successfully fitted to six groups of compounds. The equations obtained (21A to 21F), together with statistical measures of the reliability of estimate, are shown in Table 111. It is readily apparent that the scope of Equations 21A to 21F is more limiled than the scope of Equations 3A to 3F, and that the reliability of estimate is generally poorer. This result is not unexpected, since Equation 21 combines several rough approximations. I t is also evident that the reliabili' of estimate is
TABLE IV. TESTOF -Tc-
% deviationb
~
V
V
, % devitaion
-
-Pc-
%
Substance [PIG T6 Exptl. Estd.b Exptl. E8td.c Exptl. Estd.d ... 1 3 2 . 1 ' 332 575 550 -4.3 135.4 154 4-14 Bromine 77.8 7 8 . 1 : 195 304 293 -3.6 94.2 99.2 4-5.3 7 2 : s Carbon dioxide 68.9* 107 239 417 406 -2.8 123.7 131 +5.9 76.1 Chlorine 1 2 9 . 4 253 401 393 -2.0 166 59 60.6 Cyanogen 50.4* T4.0 5 1 . 0 1 6 0 . 1 282 452 458 +1.3 197.2 205 Dichlorofluoromethane ... .. . 2 8 . 4 2 8 . 3 * 352 521 514 ' -1.3 2,2-Dimethylpen- 311 tane -2.2 181.6 173 -4.7 ... 457 447 137.9 290 Ethylamine 39:i* -0.8 38.1 619 614 285 409 Ethylbenaene 44.3* +1.1 236.2 236 L'O.1 5 3 190 357 581 567 Ethylene dichloride +2.9 . , 154 49.62 62.8 375 386 120.9 238 Ethyl fluoride 34.71 -0.9 ... ... . . . 38 550 545 Germanium teti*a- 257 f 356 chloride 15.4* -3.5 14.4 1057 +0.8 1095 749 755 711 578 Heptadecane 12.80 1 1 . 9 65.0 70.5 +8.5 33.1 31.8 -4.5 33.7' 20.3 Hydrogen 3 9 . 4 8 37 239.7 241 4-0.5 -0.2 417 267 418 179 Isobut lene 40 35.2 397 -2.7 -3.1 408 3;1 752 729 491 Npphthene 77.7 71.7 103 +5.2 310 299 -3.5 97.9 8 1 . 1 a 184 Nitrous oxide -2.6 ... ... 207 313 493 480 I-Pentyne -2.4 1'9'0' 195 +i'.'s 5 8 . 0 5 2 . 3 * 444g 455 Phosgene 1 5 2 . 2 281 50.5 0 ... 125 . . . 48 92.8 161 270 270 Silicon tetrahydride (silicane) h Water 3 2 . 2 6 373 647 865 4-2.8 97.8 55.2 - 4 . 2 218.2 0 Calculated from values shown in Table I1 unless otherwise noted. b Calculated from Equations 3A to 3 F . To deviation = 100 X (estd. - exptl.)/exptl. C Calculated from Equations 13A and i 3 B . using estimated T,values. d Calculated from Equation 20,using experimental V cvalues where available, or 21A to 21F. e Experimental parachqrs. ICalculated from atomic and structural constants of Lewis and of Sugden. a Average of E uations 3C and 3E. h Correlations not apply. Indicates that Equations 21A to 2 1 F were used.
... .
.. .
I 8 *
.
*
30
I
.
deviation
TEST O F PROPOSED i'6.6 -9.5 +2.7 -1.2 -7.4
-T163 . 7
+-268 . 7
+8.9 -7.0 -4.3 12
-
f8.4
...
-6.6 f5.2
...
RELATIONS
T o provide an independent check of the proposed equations, they were applied to several compounds for which critical data were available but which had not been used in establishing the equations. The results are given in Table IV. Deviations of the calculated constants from the experimental values are in excellent agreement with the reliabilities of estimate determined from statistical considerations. I n view of the essentially empirical nature of the proposed relations, the substantiation afforded by this test provides some measure of confidence in their utility.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
November, 1944
1001
ACKNOWLEDGMENT
LITERATURE CITED
The author wishes to acknowledge gratefully the constructive criticism of this paper by 0. E. Kurt, G. F. Kirby, Jr., and G. W. Thomson, all of Ethyl Corporation; and the able assistance of Justine 5.Herzog in compiling the data.
(1) Ferguson, A.,Nat74re, 125,597 (1930). (2) Ferguson, A.,and Kennedy, S. J., I h i d . , 125,1479 (1930). (3) Gamson and Watson, Natl. Petroleum News, Sec. 2,May 3, 1944. (4) Lautie, R., BUZZ.8oc. chim., 151 2, 155,2234 (1935). ( 5 ) Ibid., 151 3, 1689 (1936). (6) Lewis, D.T., J. Chem. SOC.,1938,261. (7) Ibid., 1938,1056-61. ( 8 ) Meiasner and Redding, IND.ENQ.CnEM.,34,521 (1942). (9) Mumford and Phillips, J . Chem. SOC.,131,2112-33 (1929). (10) Othmer, D.F., IND. ENQ.CHEM., 34,1072 (1942). (11) Reilly, Joseph, and Rae, WIN., "Physico-Chemical Methods", 3rd ed., Vol. I, New York, D. Van Nostrand Co., 1940. (12) Sugden, S., "The Parachor and Valency", London, George Routledge & Sons, 1930. (13) Wohl, A., 2.physik. Chem., 87,1 (1914). (14)Ibid., 99,207 (1921).
NOMENCLATURE
[PI = parachor T, = critical temperature, K. T E = boiling point, K. Ire = critical volume, cc./mole p = pressure, atmospheres p , = critical pressure, atmospheres A , B, C, ...K; a, b, c . . . k = constants S = standard error of estimate O
O
PRESZNTED before the Division of Physical and Inorganic Chemistry a t the CHEMICAL SOCIETY, Cleveland, Ohio. 107th Meeting of the AMERICAN
Hvdrolvsis of Starch bv Sulfurous Acid J
J
J
MASON HAYEK
R. L. SHRINER
Joseph E. Seagram & Sons, Inc., Louisville 1, Ky.
Indiana University, Bloomington, Ind.
furic acid as a catalyst for the hydrolysis of starch. Berge (2) in 1897 reported the effect of the treatment of starch with sulfur dioxide. H e found that dextrins could be produced on a commercial scale by the treatment of dry potatoes with sulfur dioxide at 1 3 5 O to 140" C. Using solutions of potato starch, Berge noted that slight saccharification occurred with the use of sulfurous acid at t e m p e r a t u r e a lower than 45" C., but with increasing temperatures a greater degree
The hydrolysis of starch has been studied in the presence of sulfurous acid. Time, temperature, and concentration of sulfur '' xlde were varied, and nearly complete conversion to glucose was obtained in 15 minutes at 165" C. in the presence of 0.2 to 0.4% sulfur dioxide. Extension of this method of hydrolysis to corn mash showed that the most satisfactory conditions were a 2% concentration of sulfur dioxide at 160" C. for 15 minutes. For wheat mash the most satisfactory conditions appear to be a 2% concentration of sulfur dioxide at 165O to 170" C. for 10 minutes. The sulfur dioxide may be removed and the resulting mash fermented to produce alcohol in good yields.
in any of the hydrolyses. The distribution constant for the gas between the liquid and gaseous phases could then be calculated for any temperature between 100'and 170" C. Assuming that this constant held for all concentrations of sulfur dioxide used in the tests, the percentage of the gas in the liquid phase could be determined. This procedure is subject to error, but no better method was available. The sulfur dioxide concentra tions reported below are the corrected concentrations.
