290
J. Chem. Eng. Data 1984, 29, 290-293
in the purity of the alcohols which were used. Because of the sensitivity of GC analysis, the method was suitable for concentrations of 0. i% or less. Tables I-XIX summarize experimental measurements for systems studied. There are two interesting conclusions from studying the data. First, solubility of water in the alcohol remains quite high, even for C, and C8 alcohols where solubility of alcohol in water becomes small. Second, solubility of alcohol in the water layer first decreases with temperature, goes through a minimum at about 60 O C , and then increases with temperature. Thus, any solubility equation which assumes increasing solubility with temperature will be in error, at least over the temperature range studied here. Regktry No. I-Pentanol, 71-41-0; 2-pentanol, 6032-29-7; 3-pentanol, 584-02- 1; 2-methyl-I-butanol, 137-32-6; 2-methyl-2-butanol, 7 5 - 6 4 : 3-methyl-1-butanol, 123-51-3; 3-methyl-2-butano1, 598-75-4; 2,2dimethyl-I-propanol, 75-84-3; 1-hexanol, 111-27-3; 2-hexanol, 626-93-7:
3-hexanol, 623-37-0; P-methyl-1-pentanol, 10530-6; 3-methyCBpentanol. 77-74-7; ~thyC2+W1tW101, 108-1 1-2; I-heptanOl, 111-70-8; P-heptan~i, 543-49-7; 2,4dlmethyl-3-pentanol, 600-36-2; I-octanol, 111-67-5: 2ethyl-1-hexanoi, 104-76-7.
Literature CRed (1) Sorensen, J. M.; Ark, W. "Liquid-Liquid Equilibrium Data Collection": DECHEMA: Frankfurt/Maln, Federal Republic of Germany, 1979: Vol. V, Part 1. (2) International Union of Pure and Applied Chemistry. "Solubility Data Series"; Pergamon Press: Elmsford, NY 10523, In press. (3) Skoog, Douglas, A.; West, Donald M. "Analytical Chemistry"; Saunders College: Philadelphia, PA 19105, 1980.
Received for review August 29, 1983. Revised manuscript received February 6,1984. Accepted March 16, 1984. This work was partially supported by a grant from Stauffer Chemical Co.
Effect of Concentration on Hydrolysis Rate of Tripolyphosphate at 25 O C Joseph W. WlHlard,' Jack M. Sulllvan, and Yong K. Kim Division of Chemical Development, National Fertilizer Development Center, Tennessee Valley Author@, Muscle Shoals, Alabama 35660
The effect of concentration on the rate of hydrolyds of trlpdyphorphate at 25 OC was determinod at pH 5-7 In solutions that rangod from 4.78% to 32.3% In P205 content. The hydrotyrls rate con8tMlts were found to Increase wlth lncrearkrg total P2OScontent and decreasing pH. A general Ilnear equation was devetoped for calculathg rate con#cmto and W 4 v e s when the pH and the P20, content of trrporyphorphale soluths are known. The hydrolytic degradation of tripolyphosphate has been studied previously ( 7 - 1 7 ) . I n a previous paper ( 7 7 ) it was indicated that concentration had little effect on the firstorder rate constants for the hydrolysis of tripolyphosphate. This finding was contrary to that of previous investigators (72). However, later work (73)showed that there is an effect of concentration upon the specific rate of tripolyphosphate hydrolysis. To quantify this relationship, the rate of hydrolysis of ammonium tripolyphosphate was studied at five P2O5 concentrations and three pH levels. Experlmenlal Sectlon
The solutions to be studied were prepared by making three stock solutions that were almost saturated with (NH,),HP3010 at pH 5, 6,or 7. Portions of each stock solution were diluted with distilled water in the following proportions of stock solutin:water: 3:i, 1:1, 1:3, and i:7. These diluted solutions were adjusted to the desired pH level with gaseous ammonla or cation-exchange resin in the hydrogen form. The diluted soiutlons, along with the stock solutions, were placed in a water bath at 25 f 0.2 OC and agitated at 4 rpm. The solutions were sampled at various times (up to 1227 days) to determlne the extent of tripolyphosphate(P3O10) hydrolysis, phosphate distribution, and pH.
Total P2O5 was determined gravimetrically (74) and the ammonlacal nitrogen determined by distillation into standard acid followed by back-titration with NaOH. The pH was measured with a glass electrode. Onedimensionalpaper chrmtography (75) was used to determine the phosphate distribution as a function of reaction time.
Results and Dlscusslon The hydrolytic degradation of the tripolyphosphate ion proceeds according to the following model: k.
k.
where P3O10 represents the tripolyphosphate anionic species, and P207 and PO4 are the corresponding pyro- and orthophosphates, respectively. The hydrolysis of tripolyphosphate foibws first-order kinetics (76) in the pH and P2O5 concentration ranges studied, as shown by the plots of log % P (as P3O10) vs. time in Figures 1-3. The hydrolysis rate constants were calculated as described prevlously (16).The rate constants for P3010, k,, at each pH and P205 concentration were determined by a nonlinear regression (NLIN) of the data fitted to the equation p3°10
= (p30lO)O exp(-k3t)
(2)
where P3O10 = percent phosphorus present as P3O10 at time t , days; (P3010)o = a constant (% P as P3O10 initially present in solution): k 3= firstorder rate constant for P3Olo hydrolysis, day-'. The rate constants for P20, hydrolysis, k 2 . at each pH and total P205 concentration were determined by a NLIN computation method in which the data were fitted to the consecutive
This article not subject to U.S. Copyright. Published 1964 by the American Chemical Society
Journal of Chemical and Engineering Data. Vol. 29, No. 3, 1984 291
0
1.2 0
I
I
I
I
I
I
TIME, DAYS
Figure 3. 0 2
"
I
0 2 1 5 6 103
I
I
I
I
203
300
4co
500
Rate of hydrolysis of ammonium tripolyphosphateat 25 OC
and p~ 7.08. 600
700
TIME, DAYS
Figwe 1.
I
Rate of hydrolysis of ammonium tripolyphosphateat 25 ' C
I
I
NUMBERS ON LINES DENOTE PH
and pH 5.08.
TOTAL P20s CONCENTRATION,WT %
Figure 4. Relationshipof hydrolysis rate constant of tripolyphosphate to P205concentration and pH at 25 'C (lines are predicted vaiues from
eq 4).
I
I
I
I
I
I
0
200
400
600
800
IO00
1200
T I M E , DAYS
Flgwe 2. Rate of hydrolysis of ammonium tripolyphosphateat 25 OC and pH 6.00.
fkstader reaction model using the previously evaluated k3and (P3OlO)o values: PO ,,
= (2/3)k3(P3010)0 exp[(-k3t)/(kZ [(pz07)0 - (2/3)k3(P3Oio)o/(kz
- k3)1+ - k3)I exp(-k$)
(3)
where P207= percent phosphorus present as P207at tlme f , days: (P,O7)0 = a constant (% P as P,07 initially present in solution); k = flrst-order rate constant for P,07 hydrolysis, day-'. The measured and calculated concentrations of trlpolyphosphate for the 31.97% P205solution at pH 5 are listed in Table I (complete table is included in the supplementary material; see paragraph at end of text regarding supplementary material). The calculated rate constants, k 3 and k,, are
Table I. Distribution Changes of PzO, Species at 25 OC Starting from Tripolyphosphate" % P as time, days 0 1 2 21 22 23 56 57
100 101 210 211 365 366 449 449
p207
p3010
pH 5.08 5.07 5.05 5.08 5.07 5.08 5.06 5.06 5.07 5.10 4.99 5.00 5.05 5.04 4.98 5.00
obsd 95.4 94.9 94.3 79.9 78.4 78.3 60.3 58.6 43.7 42.8 18.4 19.8 6.0 5.8 3.2 3.3
calcd 94.6 93.9 93.1 80.3 79.6 79.0 61.0 60.5 43.2 42.9 18.2 18.1 5.4 5.4 2.8 2.8
"Solution 1: 8.20% N; 31.97% P205.
obsd 3.0 3.7 4.3 14.3 15.5 15.4 25.8 27.4 34.7 35.7 47.0 44.9 47.2 47.2 45.1 45.0
PO4
obsd 1.6 1.4 1.4 5.8 6.1 6.3 13.9 14.0 23.6 21.5 34.6 35.3 46.8 47.0 51.7 51.7
292 Journal of Chemical and Engineering Data, Vol. 29, No. 3, 1984
Table 11. First-Order Rate Parameters for Hydrolysis of Tripolyphosphate at 25 OC tripolyphosphate
no.
7 8 9 10 11 12 13 14 15
pH
day-'
day-'
pk2
5.08 5.08 5.05 5.01 5.02 6.00 6.01 6.02 6.02 6.00 7.08 7.01 7.02 7.03 7.02
78.3779 55.8381 43.0602 33.8378 30.2020 38.8253 27.7222 20.9600 15.6739 13.6083 12.6498 9.6298 7.2250 5.2360 4.8144
1.0 1.1 0.65 0.34 0.41 0.12 0.21 0.21 0.17 0.17 0.35 0.24 0.17 0.12 0.11
2.1058 2.2531 2.3659 2.4706 2.5200 2.4109 2.5572 2.6782 2.8048 2.8662 2.8979 3.0164 3.1412 3.2810 3.3175
composn, % N P,Os
soln 1 2 3 4 5 6
10-4k3,
10-4. [SE(k3)1?
8.20 6.50 4.60 2.30 1.10 9.55 7.47 5.37 2.95 1.46 9.22 7.13 5.07 2.55 1.50
31.97 24.96 17.78 9.53 4.68 32.28 25.61 18.46 10.55 5.42 28.40 22.19 15.89 8.50 4.90
10-4. t0.5,
1200-
s
v)
W
2
[SE(k&l," day-' 0.26 0.32 0.35 0.17 0.29 0.04 0.08 0.12 0.12 0.22 0.25 0.26 0.26 0.30 0.30
Pk3"
(t0S)3b
1.71649 0 0 -0.00019 0.03382 -0.00173
9138.66 -215.01 -3553.67 -0.8911 355.2111 88.3977 0.1740 -9.2613 0.999 12.69 2.53
.O 0 0.999 0.008 0.30
1000-
X
a
8
3 8
day
88.4 124 161 205 230 179 250 331 442 509 548 720 959 1324 1440
W4kz, day-' 10.7878 9.7729 9.3901 9.7557 10.8669 4.8923 4.2913 4.0438 4.0080 4.6471 1.3017 1.1985 1.0281 0.7623 0.6952
pk,
tns, day
2.9671 3.0100 3.0273 3.0107 2.9639 3.3105 3.3674 3.3932 3.3971 3.3328 3.8855 3.9214 3.9880 4.1179 4.1579
643 709 738 711 638 1417 1615 1714 1729 1492 5325 5783 6742 9093 9970
Table 111. Coefficients for Ea 4 response
NUMEERS ON LINES DENOTE pH
\
pyrophosphate
Pkz" 7.622 69 -0.126 32 -2.081 74 -0.001 54 0.227 47 0.058 19 0.000 22 -0.006 00 0.999 0.016 0.45
(to.&!b 109114.37 -2159.11 -41227.24 -16.8703 3892.7766 910.3549 2.9859 -92.9329 0.998 200.61 6.23
are half-lives "pk3= - log kB;pk2 = - log kz. ' ( t 0 , 5 ) 3 and for tripolyphosphate and pyrophosphate, respectively. R2 = multiple correlation coefficient. SD = standard deviation of predicted response values. e CV = coefficient of variation.
800-
E t-
5 !
I
NUMBERS ON LINES DENOTE pH 4
N ,
5
P
01 0
I
I
I
I
I
I
5
IO
15
20
25
30
TOTAL P205 CONCENTRATION, WT %
Figure 5. Effect of P,05 concentration and pH on half-life of tripolyphosphate at 25 OC (lines are predicted values from eq 4).
presented in Table I1 together with the standard error (SE), pk, and pk, (i.e., - log k , and log k,), and the half-life, of the tripolyphosphate and pyrophosphate ions, respectively. The pk's and half-lives of tripolyphosphate and pyrophosphate hydrolysis at 25 O C may be expressed as functlons of P20, concentration (PT, %) and pH by the general linear equation
h
-
A = a,
+ a,P, + a,pH + a,,P,* + a2,pH2 + a wPTPH
a IIZPT~PH + a 122P#H2 (4)
where the response, A , represents either pk or half-life for the hydrolysis of tripolyphosphate or pyrophosphate, respectively. The data in Table 111 show the constants for eq 4 for the various responses (A ), as well as the correlation coefficient,
"
3
I
I
5
10 15 20 25 TOTAL P205 CONCENTRATION, W T
1
1
I
1
I
30
35
Figure 6. Relationship of hydrolysis rate constant of pyrophosphate to P,O, concentration and pH at 25 OC (linesare predictedvalues from eq 4).
standard deviation, and coefficient of variation for each response. These relationships are shown in Figures 4-7. I n each figure the plotted points are the observed values and the curves were calculated by using the constants from Table I I I. As can be seen from Figure 4, the pk, values decrease when the P,05 concentration in the solution increases at the same pH value or when pH decreases at the same P,O, con-
J. Chem. Eng. Data 1084,2 9 , 293-296
293
tration on the rate of hydrolytic degradation of pyrophosphate is under way and results will be available soon. ,
Regktry NO. PO , -:,l
14127-68-5.
Llterature Clted (1) Crowther, J. P.; Westman, A. E. R. Can. J . Chem. 1954, 32, 42-8. (2) Van Wazer, J. R.; &lffith, E. J.; McCullough, J. F. J. Am. Chem. Soc , 1955, 77, 287-91. (3) Green, J. Ind. Eng. Chem. 1950, 42, 1542-6. Frless, S. L. J. Am. Chem. SOC.1952, 74,4027-9. (4) (5) Shen, C. Y.; Dyroff, D. R. Ind. Eng. Chem. Prod. Res. D e v . 1966, 5,
97-100.
(6) Shen, C. Y.; Metcalf, J. S.; O'Grady, E. V. Ind. Eng. Chem. 1959, 51,
0
5
10
15
20
25
30
35
TOTAL P205 CONCENTRATION, WT %
Flgure 7. Effect of P205concentration and pH on half-life of pyrophosphate at 25 O C (lines are predicted values from eq 4).
centratlon. Therefore, the tripolyphosphate hydrolyzes most rapidly at high P,05 concentrations and low pH values. The same effect of P,O5 concentration and pH upon the half-life of tripolyphosphate is shown in Figure 5. I n the case of pyrophosphate, pk, values decrease when the P,O5 concentration increases at pH 7, but the effect is negligible when the pH is 6 or less (Figure 6). The data in Figure 7 show the half-life of pyrophosphate as a function of P,O5 concentration and pH. A study of the effect of P,05 concen-
717-8. (7) Quimby, 0.T. J . Phys. Chem. 1954, 58, 603-18. (8) Bell, R. N. Ind. Eng. Chem. 1947, 39, 136-40. (9) GriffAh. E. J. Ind. Eng. Chem. 1959, 51, 240. (IO) Thllo, E. Angew. Chem., I n t . Ed. Engl. 1965, 4, 1061-71. (11) Farr, T. D.; Wllllard, J. W.; Hatfieid, J. D. J. Chem. Eng. Data 1972, 17, 313-7. (12)Van Wazer, J. R. "Phosphorus and Its Compounds"; Interscience: New York, 1966;Vol. 1. (13) Frazler, A. W.; Dlllard, E. F. J. Agrlc. FoodChem. 1961, 29,695-8. (14) Perrln, C. H. J. Assoc. Off. Anal. Chem. 1958, 41, 758-63. (15) Karl-Kroupa, E. Anal. Chem. 1956, 28, 1091-7. (16) Wllllard, J. W.; Farr, T. D.; Hatfield, J. D. J . Chem. Eng. Data 1975, 20.276-a3. Recelved for review June 7, 1983. Revised manuscript received November 14, 1983. Accepted January 20, 1984. Supplementary Materlal Available: Complete Table I (calculated vs. , , and observed PO, at observed concentrations of P,OlO, observed PO 25 "C) (8pages). Ordering informatlon is given on any current masthead page.
Excess Thermodynamic Functions for Ternary Systems. 11. Total-Pressure Data and GE for Ethylene Glycol/Acetone/Water and for Ethylene Glycol/Acetonitrile/Water at 50 C Mlguel A. VlllamaTibn,t Ahmed J. Allawl, and Hendrlck C. Van Ness" Chemical and Environmental Engineering Depatfment, Rensselaer Polytechnic Institute, Troy, New York 12 18 1
Isothermal P-x data for the ternary systems ethylene glycol/acetone/water and ethylene glycol/acetonHrlle/water at 50 OC are reported. Data reductlon by Barker's method provldes correlations for 0
=.
Vapor/iiquid equilibrium measurements are reported for ethylene glycol/acetone/water and for ethylene glycoVacetonitrile/water at 50 OC. Experimental values of total vapor pressure are measured for ternary mixtures formed by addition of a pure species to mixtures of the other two. The data for ethylene glycol/acetone/water come from seven such runs and for ethylene glycol/acetonitrile/water from five. Data are also reported for the binary system acetonitrile/water. Correlations for the ethylene glycol/water, acetonelwater, ethylene glycoVacetone, and ethylene glycol/acetonltrile binaries have already been published ( 1-3). The apparatus was that of Gibbs and Van Ness (4) as modified by DiElsi et al. (5). For the ethylene giycoVacetone/water system, the ethylene glycol was chromatoquality reagent Permanent address: Dpto. de Termologia. Facultad de Ciencias, Universidad de Vailadoll, ValladolM. Spain.
0021-9568/84/1729-0293$07.50/0
with specified purity of >99.5 mol % from Matheson Coleman and Bell, and the acetone was OmnlSolv reagent with an indicated purity of 99.5 mol % from MCB Manufacturing Chemists, Inc. For the ethylene glycol/acetonitrHe/water system, the ethylene glycol was 99+ mol % reagent from MCB Manufacturing Chemists, Inc., and the acetonitrile was chromatoquality reagent with stated purity of >99.9 mol % from Matheson Coleman and Bell. The water was doubly deionized. All reagents were thoroughly degassed.
Results and Correlatlons Table Ipresents data for ternary mixtures of ethylene glycol/acetone/water. Table I 1 shows P-x data for the acetonitrilelwater binary system, and Table I11 gives data for the ethylene glycol/acetonitriie/water ternary. Data reduction is by Barker's method, as described earlier (6, 7). For the binary systems, the Margules equation with up to six parameters provides suitable expression of GE:
The binary system for which data are reported here requires all six parameters. Values for this system as well as for those
0 1984 American
Chemical Soclety
