June, 1926
INDUSTRIAL A N D ENGINEERING CHEMISTRY
633
Vapor Pressure of Aqueous Solutions of Nitric Acid' By Guy B. Taylor E X P E R I M E N TSTATION, AL E. I. D U PONTDE NEMOURS & Co., WILMINDTON, DEL.
Since Carpenter and Babor give no temperatures, their OSCOE'v* an early worker in field, showed that 68 per cent nitric acid exhibited a constant boiling point a t results have been combined with Creighton and Githens' atmospheric pressure and that the composition of the boiling temperatures a t 760 mm. First a plot of boiling temperatures against composition was constructed from data constant-boiling acid varied but little with the pressure. Creighton and Githens2 confirmed Roscoe's observations given in Creighton and Githens' paper. From this plot and determined the boiling points of 20 to 100 per cent acid temperatures were read off corresponding to Carpenter and at four pressures. The composition of the vapor in equilib- Babor's compositions. The latter's vapor compositions as given in weight per cent were calculated to partial pressure rium with the boiling acid was not determined. Carpenter and Babor3 determined compositions of vapor nitric acid by first converting weight per cent to mol fraction and multiplying this figure in equilibrium with nitric by 760. a c i d s o l u t i o n s of a l l The data of Berl and strengths when boiling a t This paper comprises a literature review of all the Samtleben and of Pascal atmospheric pressure. No existing data on the vapor pressures of nitric acid were calculated in the same temperatures were detersolutions and a compilation of the most probab!e values way. mined. of the partial pressures of nitric acid and water from Burdick and Freed and Berl and Samtleben' obsolutions containing 20 to 90 per cent nitric acid and of Sproesser and Taylor give tained data of the same nitric acid from the pure acid. The appended table their data directly in partial nature as Carpenter and is the result of the work. Partial and total pressures pressures. Babor but did determine are given from 0" C. to a little above the boiling point. Klemenc expresses his temDeratures. T h e i r results are not very different I I a c i d comDos-itions bv normality. * Conversion & from Carpenter and Babor's though probably not so accurate owing to the fractionat- his figures to weight per cent requires a knowledge of the temperature a t which normality was determined in order to arrive ing effect of the thermometer. Pascal,6 also by a distillation method, determined the tem- a t figures for density. Fifteen degrees Centigrade was asperatures and vapor compositions a t different pressures. sumed and a standard density table was used. This makes His work covers a considerably greater range than the authors, his highest concentration a trifle over 100 per cent, asjust cited, but unfortunately his results are somewhat er- suming 12.5' C. will not change the figures appreciably for weight per cent. .ratic. As a preliminary orientation the data were plotted on arithBurdick and Freed* used the method of aspirating air through solutions held a t constant temperature, absorbing log paper, log p vs. 1/T. From this plot it was evident that the acid and water from the air stream, and calculating pres- the data of Creighton and Githens, Carpenter and Babor, sures from the data so obtained. They covered the range Burdick and Freed, and Sproesser and Taylor were more consistent among themselves and with each other than those 24 to 70 per cent nitric acid a t 25", 50°, and 75" C. Sproesser and Taylor' by a similar method covered the of the other observers. The best lines that could be drawn same range as Burdick and Freed, and attempted to apply were then placed on the plot for acid strengths from 20 to 70 per cent a t 5 per cent intervals from the data of these four the method to higher concentrations. Klemenc,8 also by an aspiration method, measured the papers. The data do not justify curving these lines; hence partial pressure of nitric acid out of acids 10 to 100 per cent they were drawn straight, the slopes increasing with decreas"03 a t 12.5' C., and in a few cases that of water vapor. ing acid concentration for the nitric acid partial pressures and being practically parallel with the line for pure water in the He also gives a few results a t 30" C . Saposhnikoffg gives some data a t 15' C. on acids ranging case of the water partial pressures. For 100 per cent HNOI nitric acid the data of Creighton and from 66 to 98 per cent nitric acid. The nitrogen content of the vapors as given indicates serious decomposition into lower Githens and of Pascal agree very well a t the higher temperaoxides. His data for the purpose in hand are of little or no tures, but Pascal's pressures are lower a t the lower temperatures. The data of Creighton and Githens, when plotted value. log p vs. 1/T, give a pronounced curve concave downwards. Discussion Pascal's data give considerably more curvature and for I n working up the data, the results of References 2 to 8, this reason were not given so much weight in the choice of inclusive, were calculated so that partial pressures of water final data. Consistent data over any considerable range for acids and of nitric acid could be plotted as logarithms against the between 70 and 100 per cent nitric acid are lacking. Drawing reciprocals of the absolute temperature. Creighton and Githens give only total pressures. The curves for these concentrations was largely guess work and vapor from 99.79 per cent acid can be considered wholly the values less reliable than for other concentrations. Carnitric acid and that from the constant boiling mixtures the penter and Babor's single points for each acid concentration are probably reliable, but obviously straight lines projected same composition as the boiling residue. from these points consistent with concentrations of 70 per cent 1 Received March 6, 1925. This work was done specitically for Inand under would be inconsistent with the curvature of the ternational Critical Tables on an assignment under the subeditorship of 100 per cent line. Klemenc has one point in this region a t F. C. Zeisberg. *Numbers in text refer to bibliography at end of article. 12.5' C. that might serve as a basis for extrapolation of the
R
INDUSTRIAL AND ENGINEERI.VG CHEMISTRY
634
Vol. 17, No. 6
Vapor Pressure of Nitric Acid S o l u t i o n s i n M i l l i m e t e r s Mercury
c.
"0%
...
0 5 10 15 ..
20 25 30 35 40 45 50 55 60 65
... ... ...
...
0.09 0.13 0.19 0.27 0.38 0.53 0.74 1.01 1.37 1.87 2.50
70
75 80 85 90 95 100 105 110
c. 0 5 10 15 a0 25 30 35 _. 40 45 50 55 60 65
7Q
75 .. 80 85 90 95 100 105 110 115 120 125
a
c.
0 5 10 15 .. 20 25 30 35 40 45
50
55 60 65 70 75 80 85 90 Q5 .~ 100 105 110 115 120 125
20~~------.
-25%
7---
-40%-
"03
... ... ... ...
...
0.12 0.17 0.25 0.36 0.52 0.75 1.04 1.48 2.05 2.80 3.80 5.10 6.83 9.0 11.7 15.5 20.0 25.7 32.5
Ha0
Total
4.1 5.7 8.0 10.9 15.2 20.6 27.6 36.5 47.5 62 80 100 128 162 200 250 307 378 458 555 675 800
4.1 5.7 8.0 10.9 15.2 20.6 2'7.6 36.5 47.5 62 80 100 128 162 200 250 308 379 459 556 677 803
H20
Total
3.0 4.2 5.8 8.0 10.8 14.6 19.5 25.5 33.5 43 56 71 90 114 143 178 218 268 325 394 480 573 688 810
3.0 4.2 5.8 8.0 10.8 14.7 19.7 25.7 34.0 44 57 72 92 116 146 182 223 275 334 406 495 593 714 843
7 6 5 % - H~O 1.3 0.41 1.8 0.60 2.6 0.86 3.5 1.21 4.9 1.68 6.6 2.32 8.8 3.17 11.6 4.26 15.5 5.70 20.0 7.55 26.0 10.0 33.0 12.8 43.0 16.8 54.5 21.7 68 27.5 35.0 86 43.5 106 131 54.5 160 67.5 195 83.5 103 238 288 124 152 345 410 181 218 490 580 260
... ...
... ... ... ... ... .. .. ..
0.09 0.13 0.18 0.28 0.40 0.54 0.77 1.05 1.44 1.95 2.62 3.50 4.65
-45%-
"Os
... ...
... 0.10 0.15 0.23 0.33 0.48 0.68 0.$6 1.35 1.83 2.54 3.47 4.65 6.20 8.15 10.7 13.7 17.8 23.0 29.2 37.0 46
Total 1.7 2.4 3.5 4.7 6.6 8.9 12.0 15.9 21.2 27.6 36
8
76 96 121
150
186 228 279 341 412 497 59 1 708 840
Total
3.8 5.4 7.6 10.3 14.2 19.2 25.7 33.8 44 57.5 75 94 121 151 187 234 287 352 426 517 628 745
3.8 5.4 7.6 10.3 14.2 19.2 25.7 33.8 44 57.5 75 94 121 151 188 235 288 353 428 520 632 750
Ha0
Total
2.6 3.6 5.0 6.8 9.4 12.7 16.9 32.3 29.3 38.0 49.5 62.5 80 100 126 158 195 240 2%2 355 430 520 625 740
2.6 3.6 5.0 7.0 9.5 13.0 17.2 22.8 30 39 51 64 83 103 131 164 203 251 306 373 453 549 662 786
70%-
7--
HN03
0.79 1.12 1.58 2.18 3.00 4.10 5.50 7.30 9.65 12.6 16.5 21.0 27.1 34.5 43.3 54.5 67.5 83 103 125 152 183
HLO 1.1
1.6 2.2 3.0 4.1 5.5 7.4 9.8 12.8 16.7 21.8 27.3 35.3 44.5 56 70 86 107 130 158 192 231 270 330 393 469
--50%-
"01
...
o:ii
0.18 0.27 0.39 0.56 0.80 1.13 1.57 2.18 2.95 4.05 5.46 7.25 9.6 12.5 16.3 20.9 26.8 34.2 43.0 54.5 67 84
Total
1.9
2.7 3.8 5.2 7.1 9.6 12.9 17.1 22.5 29.3 38.3 48 62 79 99 124 154 190 233 283 344 414 49 1 592 705 84 1
nitric acid partial pressures, but one point is hardly enough. Klemenc's values in general appear to be very good. Heat effects can be used as a rough check on the vapor pressure data. The following familiar vapor pressure equa&n applies to both the nitric acid and water Partial Pressures: log b =A -_
- Z.6BK1
-30%-
Ha0
" 0 3
(1) . .
In this equation B is the total heat of evaporation and B/2.3 R is the slope of the vapor pressure curve. The latent heat of nitric acid (100 per cent) calculated from the slope of the final vapor pressure curve comes out 7500 calories a t 80" C. and 7800 at 20" C. The experimental value of Berthelot is 7250 calories per mol nitric acid. For tfhe solutions of nitric acid B is the sum of the latent
HNOa
Total
0.11 0.17 0.25 0.35 8.51 0.71 1.00 1.38 1.87 2.53 3.38 4.53 6.05 7.90
HzO 3.6 5.0 7.1 9.7 13.2 17.8 23.8 31.1 41 53 69 87 113 140 174 217 267 325 393 478 580 690
3.6 5.0 7.1 9.7 13.2 17.8 23.8 31.1 41 53 69 87 114 141 175 218 269 328 396 483 586 698
HzO
Total
-55%"01
Hz0
2.1 3.0 4.2 5.8 7.9 10.7 14.4 19.0 25.0 32.5 42.5 54 70 88 110 138 170 211 258 315 383 463 560 665 785
2.1 3.0 4.3 5.8 8.2 11.1 15.0 19.8 26.1 34 45 57 74 93 117 148 182 227 279 342 417 506 615 732 869
... ... ...
...
------8O%-
"Os
2
3
4
6 8 10.5 14 18.5 24.5 32 41 52 67 85 106 130 158 192 230 278 330 392 465 545 640
Ha0
... ...
1.2 1.7 2.4 3.2 4 5.5 7 9.5 12 15 20 25 31 38 48 60 73 89 108 129 155 185 219
...
... ... ... ... ... ...
0.09 0.13 0.20 0.28 0.42 0.59 0.85 1.18 1.63 2.26 3.07 4.15 5.50 7.32 9.7 12.7 16.5
3.r 5.2 7.2 9.8 13.1 17.4 23.1 30.5 39 7 51 66 84 106 134 166 205 252 309 378 459 558 665 795
go%---
"01
2 3 5 8 11 14 18 24 32 42 53
... ...
2;
.
1.5 2.1 3.0 4.1 5.6 7.7 10.3 13.6 18.1 23.7 31.0 39 51 64 81 102 126 156 192 233 285 345 417 495 590 700
I
...
1 1.3 1.8 2.4 3 4 5 6.5 8 10 13 16 20 24 29 35 42
Tntnl
1.7 2.4 3.4 4.7 6.4 8.9 12.0 15.9 21.2 28 37 46 61 77 98 124 154 191 236 288 354 430 520 621 746 887
%&%"
6 8 11 15 20 28 37 49 64 83 107 132 163 200 242 295 354 425 504 599 710 832
... .
H10
Total
Hz0
5.5 8 11 15 20 27 36 47 62 80 103 127 157 192 232 282 338 405 480 570 675 790
110 137 168 206 252 303 367 438 521 620 730 859
3.3 4.6 6.5 8.9 12.0 16.2 21.8 28 4 38 48 63 80 103 128 161 200 246 30 1 365 443 540 644 772
0.19 0.28 0.41 0.59 0.84 1.21 1.66 2.28 3.10 4.20 5.68 7.45 9.9 13.0 16.8 21.8 27.5 34.8 43.7 55.0 69.5 84.5 103 126 156 187
2.2
r
Total
Total
3.3 4.6 6.5 8.9 12.0 16.2 21.7 28.3 37.7 48 63 79 102 127 159 198 243 297 359 436 5313 631 755
"OR
1.8
0.14 0.21 0.31 0.45 0.66 0.93 1.30 1.82 2.50 3.41 4.54 6.15 60 8.18 76 10.7 95 13.9 120 18.0 148 23.0 182 29.4 223 37.3 272 47 331 58.5 400 73 485 90 575 110 686
HIO
-SO%--
Total
1.8 2.5 3.5 4.9 6.7 9.1 12.2 16.1 21.3 28 36.3 46.0
-35%
"01
11 15 22 30 42 57 77 102 133 170 215 262 320 385 460 540 625 720 820
heat and the heat of dilution. According to Thomsen the heat of dilution is expressed by the formula 8974 n (2) , -..-. H = calories evolved in diluting 1 mol HNOs with n mols HtO h = calories evolved in diluting 1 mol H20 with Nmols HNOs =
Then whence
N C 1 7 . 1 7 .r
h = NHandn = h=
8974
1 13
N
(3)
1 f 1.737 N
The heat of dilution to be added to the latent heat is that of mixing 1 mol of either HNO, or H20 to an infinite body of acid represented by compositon n 1 or by N 1, which is obtained by differentiating Equations 2 and 3.
+
+
June, 1925
I S D r S T R I A L A N D ENGINEERING CHEMISTRY dH 15,600 _ -dn (n 1.737)?
for the nitric acid partial pressures. With nitric acid the plotted results actually show this to be the case. With water the lines are nearly parallel, as they should be because the value of B varies little with concentration.
+
dh= dN
8974
+ 1.737 N ) 2
(1
-4few calculations of B with the aid of Equations 4 and 5 follow, taking the latent heat of " 0 3 to be 7500 calories and of H20, 10,OOO calories. Per cent d z & B B HXOa by weight 20 40 70
n 14.0 5.25 1.50
N 0.071 0.19 0.67
dn 63 320 1490
dN 7410 5070 1920
635
Ha0
10,063 10,320 11,490
HNOa 14,610 12,570 9,420
According to the above the slopes of the log p vs. 1/T lines should increase with increasing concentration for the water part'ial pressures and decrease with increasing concentration
Bibliography I-Roscoe, J . Chem. SOC.(London), 13, 146 (1861). 2-Creighton and Githens, J . Franklin Insl., 119, 161 (1915). 3-Carpenter and Babor, Am. Insl. Chem. Eng., preprint Denver meeting, July, 1924. 4-Berl and Samtleben, 2. angew. Chem., 36, 201 (1922). 5-Pascal, Mem. poudres, 20, 4 0 (1923). 6-Burdick and Freed, J . A m . Chem. SOC.,43, 526 (1921). 7 S p r o e s s e r and Taylor, Ibid., 43, 1784 (1921). 8--Rlemenc, Vienna, private communication, August 1, 1924. 9-Saposhnikoff, 2. p h y s . Chem., 13, 225 (1905).
Hygroscopicity and Cakiness of Fertilizer Materials' By A. B. Beaumont and R. A. Mooney ?vf ASSACHUSETTS AGRICULTURAL COLLBGE, AMHERST,MASS.
HE behavior of fertilizer materials stored under different conditions of humidity is important to the manufacturer, dealer, and consumer of fertilizer materials or mixed goods. There is little in the literature bearing on the subject. Van Harreveld-Lako2 investigated the hygroscopicity of several nitrogenous materials under the conditions of humidity prevailing on the island of Java, and Edgar and Swan3 determined the vapor pressures of the saturated solutions of several types of fertilizer materials. The results of a study of the hygroscopicity and cakiness of eighteen fertilizer materials and three mixtures under conditions of temperature and humidity prevailing in Massachusetts during the summer season, the season of greatest humidity, are here reported. The average mean monthly temperature for June, July, and August for the period 191923 was 20.1' C., and the average mean monthly relative humidity for this period was 78.0 per cent. The maximum relative humidity for the same period was 97.5 per cent. These two points of humidity, as well as the point midway between them-namely, 87.75 per cent-were chosen for study. The relative humidities of 73.0 and 68.0 per cent were selected as having the greatest promise of establishing conditions under which no moisture would be absorbed, based upon calculations involving Edgar and Swan's data.
When samples were very moist it was necessary to give them a preliminary drying in a desiccator before subjecting them to the higher temperature, in order to prevent "crawling." For the study in cakiness the materials were exposed in a similar manner, except that the amount of acid was increased to correspond with larger amounts of material used and the time was extended to 14 days. After exposure the material was immediately transferred to molds of LL1/pinch"(1.6 cm. inside diameter) brass pipe 3.2 cm. long, greased, and lined with paper to prevent sticking, and with the exception of muriate of potash and ammonium nitrate, which were dried in an oven a t 40" C., were allowed to dry a t room temperature. After drying, the cylinders of caked fertilizer were cut to 1.28-cm. lengths and placed in a testing machine for determination of the crushing strength. Sufficient replicate determinations were made in each case to reduce the experimental error, which was found to be especially high in the crushing tests, to a point where differences might be significant. I n the humidity determinations five to ten replicates were run and in the crushing tests it was necessary to run five to twenty-nine tests. The probable error of the mean of each series of tests u-as worked out by Peter's formula.
Methods
Table I-Materials
T
The static method was employed. Desiccators (15.2 cm. diameter) were converted into humidors and dilutions of sulfuric acid based upon tables of Landolt-Bornstein and Roth were used to maintain the necessary conditions of humidity. All determinations were conducted in a constant-temperature room maintained a t 20.1" C. The material studied, all passing a 0.5-mm. sieve, was placed in aluminium boxes (5.1 cm. diameter) to the depth of 5 to 7 mm., and the boxes were placed on a coarse wire screen support immediately over the sulfuric acid solution and exposed for 7 days, 200 cc. of acid being used in each humidor. The inorganic materials were dried to a constant weight a t 130" C. according to the official method,4 and organic substances were dried a t 100" C. 1
2
3 4
p. 1 .
Received March 2, 1925. d r c h . Suikerind., 20, 1254 (1921). J . A m . Chem. SOL.,44, 570 (1922). .4ssoc. Ofiicial Agr. Chem., Methods, Revised to November 1, 1919,
Results Phosphoric Ammonia acid Potash MATERIAL Per cent Per cent Per cent ilmmonium nitrate (crystalline), , , . , , 40.07 Ammonium nitrate (granular) . , ., , , , . 41.20 Ammonium sulfate.. . . . . . . . . . . . . . . . 24.96 ... 32.50 Ammonium sulfate nitrate . . . . . . . . . . ... Calcium cyanamide. . . . . . . . . . . . . . . . .. . . . 2 4 . 2 8 ... ... Calcium nitrate, . . . . . . . . . . . . . . . . . . .. . . . 1 5 . 7 8 ... ... Sodium nitrate.. . . . . . . . . . . . . . . . . . . . . . . 1 8 . 2 1 ... ... Urea. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5 . 5 0 ... .,. Cottonseed meal. . . . . . . . . . . . . . . . . . .. . . . 7.28 3.00 1.00 Dry ground f i s h . . . . . . . . . . . . . . . . . . . . . . 9.00 LO0 ... . . . . 9.99 4.58 ... Bone m e a l . , . . . . . . . . . . . . . . . . . . . . . . .. . . . 4.83 24.00 ... Acid phosphate.. . . . . . . . . . . . . . . . . . . . 16.00 ... ... Calcined phosphate . . . . . . . . . . . . . . .. . . . ... 27,00 ... Rock phosphate.. . . . . . . . . . . . . . . . ... 32,OO Kainite. . . . . . . . . . . . . . . . . . . . . . . . . . . . ... ... 12:oo Muriate of potash . . . . . . . . . . . . . . . . . . ... ... 50.00 Potassium sulfate. . . . . . . . . . . . . . . . . . . . . ... ... 48.00 "4-8-4 4 8 4 4 4 8 (3j 4 4 8 (1) Made of nitrate of soda, acid phosphate, and muriate of potash; no filler added. (2) Same as (1) except half of ammonia was supplied by tankage; no filler added. (3) Same as (1) except peat was added as filler.
... ... ...
(3
it),
