Comparison of Ammonia, Carbon Dioxide, and Water Analysis of Known Mixtures. T o determine the accuracy of the entire procedure, analyses were made on mixtures with known vapor pressures of ammonia,
nitrogen. The 1.38-micron water band showed that both temperature and pressure effected the molar absorptivity. A mathematical study showed that the effect could be expressed by the following equation : =
B
+ 0.0071 Xi
0.555
0.00053
X1 = (P - 75)/10 Xz = (TOK - 385)/6 =
T
= absolute temperature
c
=
pressure in mm. of H g (OK.)
molar absorptivity
The molar absorptivity of the 1.53micron ammonia band showed only a small variation with increased pressure. The molar absorptivity changed from 0.389 at 15 p.s.i. to 0.407 a t 60 to 90 p s i KO temperature effect was observed up to a temperature of 130’ C.
Table 1.
Vapor-Liquid Equilibrium Data
Total pressure mm. of Hg Obsd. Calcd.
Vapor phase
c.
Gas NHI HVO NHz
82.5 100 8
Perry’s
H-0 --._
NHo H20 NHI HzO
122.9 126.3
(1)
X22 carbon dioxide, and water. An ammonia-water composition was taken from Perry’s Chemical Engineering Handbook (3). Table I compares the data obtained by analysis with that from the Handbook. The difference between the readings was less than f 1%. A second analysis was made from a liquid composition of ammonia, carbon dioxide, and water obtained from references 3 and 4. The results are shown in Table 11. The difference between the sum of the partial pressure of the ammonia, carbon dioxide, and
where
P
+ 0.0004 XlXz - 0.0016 X i 2
- 0.0090 Xz
-
5 0 . 2 wt. % ’ 4 9 . 4 wt. 9 54 8 wt. % 45 _ _ -2 wt. 9 3050 mm.’Ef 1350 mm. of 3250 mm. of 1450 mm. of
Found
Hg Hg Hg Hg
5 0 . 6 wt. % ’ 4 9 . 8 wt. 9n 55 5 wt. % 44 .5 wt 92900 mm.’if Hg 1335 mm. of Hg 3150 mm. of Hg 1360 mm. of Hg
735
737
1363
1362
4235
4270
4510
4610
water gases and the total pressure varied between 3 and 5%. High results of this magnitude are probably due to air in the reaction cell introduced when the cell is charged. Calculations. Since the absorbance is directly proportional to the number of gas molecules in the light path, the partial pressure of ammonia and water can be calculated by use of the ideal gas law and Beer’s law, as expressed in the following equation.
The partial pressure ( P ) will be in millimeters of mercury when R is 62.360 liters millimeter Hg(OK.)-I(gram mole)-’. Temperature T is in OK., b is cell path length in centimeters, A h is absorbance at subscript wavelength A, and is the molar absorptivity. The molar absorptivity for water was obtained from Equation 1. Experimental results are listed in Table 111. When the log of the partial pressure was plotted against the reciprocal of the absolute temperature linear curves were obtained. A typical plot is shown in Figure 3. The linear plot indicates no other compounds are formed in the liquid phase. The partial pressures from duplicate runs agreed within 10%. In almost all cases, the sums of the partial pressures were within 10% of the observed total pressures. LITERATURE CITED
Table II.
Vapor-Liquid Equilibrium Data of Ammonia, Carbon Dioxide, and Water System
c.
Partial pressure (mm. of Hg) Otsuka ( 2 ) Krishna ( I ) Exptl.
Component
100
603 105 812 1520
“I
co, - -_ Hz0 Total Obsd.
337 30 362 729
Total Obsd.
Liquid phase mole 7 0 NHI COz 14.5
14.5
258
4.98
690 178 769 1637 1690 395 35 355 790 830
...
80
Table 111.
695 130 795 1620
...
...
RECEIVED for review September 16, 1964. Accepted November 19, 1964.
Vapor-Liquid Equilibrium of Ammonia, Carbon Dioxide, and Water System 1
Temperature 0 c . I / T 103 73.5 69.2 79.2 85.6 89.6 92.3 89.2 89.1
2.889 2.922 2.839 2.789 2.758 2.737 2.761 2.762
5.0
ANALYTICAL CHEMISTRY
.
Total P mm. of Hg P mm. of Hg NH1 COz H2O Calcd. Obsd.
-
764 0 600 0 616 0
222 242 366 468 54,5 574 509 507
0 0 0 0 0 0 0 0
o
293
o o
490 415 593 728 831 948 850 847
0 0 0 0 0 0 0 0
49n
n
211
0 0 0 0
i42 443 356 774 573
433 714 602 916 840
0
179 126 282 454
0 5 5 0
o 0 0 0
0
248 455 367 571 519
0 0 0 0
891 783 1241 1650 2286 1959 1970 994 823 1612 1325 2261 1932
( 1 ) Krishna, hI. G., Ph.D. thesis, Leeds University, England, 1948. (2) Otsuka, E., Yoshimura, S., Yakabe, M., Inone, S., J . Chem. SOC.Japan 6 3 , 1214-18 (1960). (3) Perry, John Hj.; “Chemical Engineering Handbook, 3rd ed., p. 1685, McGraw-Hill, 1950. (4) Van Krevelen, D. W., Hoftixer, P. J., Huntjens, F. J., Rec. Trav. Chzm. 68, 191-216 (11949).
862 741 1074 1382 1635 1794 1614 1604 851 735 1338 1197 1853 1593
Correction Compositional Analysis of n Component Systems by X-Ray Absorption Method In this article by Robert Lefker [ANAL.CHEM.36,1877 (1964)l there are terms which are defined incorrectly in formula ( 1 ) . The correct definitions are as follows: mass absorption coefficient of nth component d = px where p = density of unknown z = thickness of unknown.
k, =
All formulations are correct if these changes in defined terms are applied.
