I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
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obtained. I n addition the control as well as carbonated zinc oxide used was photographed by the electron microscope. These photographs appear in Figure 5. From this information it is readily seen that the Carbonated material as well as the acicular crystals of zinc ovide have much less surface than the uncarbonated control or the zinc oxide materials of smaller particle size.
Aclcnowledgmen t The paints used in this study were prepared in the Allied Research Laboratory of The Sherwin-Williams Company. The Graflex fingerprint camera and the constant temperature-humidity room, used to age the panels prior to exterior exposure, are the property of the United States Regional Soybean Laboratory. The electron microscope photographs included in this paper were obtained with the assistance of Martha Barnes, of the University of Illinois. Literature Cited (1) Anderson, A. W., P a i n t , Oil Chem. Rev., 97, No. 8 , 42-3 (1935). (2) Anderson, G., Paint Varnish Prodiiclion Mgr., 15,22-4 (1936).
Vol. 34, No. 8
(3) Brandt, R.W., Metal Cleanzng Finishing, 3,499 (1931). (4) Bunce, E. H., Am. Paint V a r n i s h Mfrs.Assoc. Circ. 319, 541 (1927). (5) Depew, H . A., P a i n t , Oil Chem. Rev., 102,No. 17, 9 (1940). (6) Eide, A. C., and Depew. H . A., Am. P a n t J.,20, 7 (1936). (7) Foulon, A., Allgem. Oel- u . Fett-Ztd., 34, 131 (1937). (8) Hoek, C. P. van, Farben.-Ztg., 33, 2789 (1928). (9) Kamp, Paul, Farbe u. Lack. 1930.291. (10) Kekwick, L. O., and Pass, A, Paint Varnish Production Mgr., 13, 296 (1938). (11) Merabacher, S., Chem. Umschau Fetts, Oele, Wachse Harze, 35, 17.1 . flR38) (12) Nelson, H. A,, Am. Paint J . , 15, No. 28, 20 (1931). (13) Newman. R. M., Paint, Oil Chem. Reo., 97,No. 21, 56 (1935). (14) Pupil, F., Recherches inventions, 17, 226 (1936). (15) Rigolot, H., Bull. soc. encour. i n d . n d . , 9, 990 (1907). (16) Rosser, E. O., Kunststoffe, 16, 170 (1926). (17) Tauber, Ernst, Farben-Ztg., 17, 1888 (1912). (18) T r o t t , L. H., New Jersey Zinc Co., Research Bull., 1928. \ _ _ _ _
PRBSENTED before the Division of Paint, Varnish, and Plastics Chemistry a t CHEMICAL SOCIETY, Memphis, Tenn. the 103rd Meeting of the AMERICAX A portion of this work constituted part of the thesis submitted by T. W. Mastin for the degree of master of science in chemistry in the Graduate School of the University of Illinois.
The System Nitric Acid-Sulfuric Acid-Water J
ENTHALPY-TEMPERATURE NOMOGRAPH J. LLOYD MCCURDY AND CLYDE MCKINLEY
I
N T H E preparation of mixed acids for nitration processes, as well as in the nitration reactions themselves, the temperature and, as a result, the heat balance of the system is of prime importance. Recently a correlation of all available heat content, specific heat, and heat of mixing data for the ternary system nitric acid-water-sulfuric acid was presented as a summarized enthalpy and specific heat plot, with examples for its use in heat balance calculations1. Owing to the importance of such reactions it has seemed advisable to present this data in a nomograph t o facilitate its use. A solution is presented in Figure 1 to calculate the change in enthalpy of mixed-acid ternary mixtures with increase or decrease in temperature. Figure 2 shows the relative enthalpy of the ternary system referred to each pure component at 32" F. That is, each component in the pure state has zero enthalpy a t 32" F. By the use of Figure 2 in combination with Figure 1 it is possible t o determine the enthalpy of any acid mixture a t any temperature relative to the above base and the consequent change in enthalpy with change in temperature. With these charts it is relatively simple to make heat balance calculations for any system containing these components. The nomograph (Figure 1) solves graphically the relation:
H where H C,
At = 1
=
CpAt
= change in enthalpy of 1 lb. of mixture = s ecific heat of 1 lb. of mixture
cfkqge in temperature of 1 lb. of mixture
McKinley, C., and Brown, G. G., Chem. &. M e t . Eng. 49, 142 (1942)
(1)
University of iMichigan, Ann Arbor, Mich. Since the specific heat is a function of acid composition,
C, does not appear on the nomograph; instead, acid compositions are plotted in such a way that Equation 1 is solved, To find the relative enthalpy of one pound of mixed acid containing 60 per cent sulfuric acid, 20 per cent nitric acid, and 20 per cent water a t 100" F., for example, it is necessary to read the relative enthalpy of this mixture a t 32" F. from Figure 2 and then add the change in enthalpy for the temperature change, 32' to 100" F., as given by Figure 1:
% "Os
(anhydrous or water-free basis)
yototal acid
=
20
+ 60 = 80%
=
20/80 X 100 = 25%
From Figure 2 for 25 per cent nitric acid (anhydrous basis) and 80 per cent total acid, the relative enthalpy a t 32" F. is read as -108 B. t. u. per pound of solution. On Figure 1 the acid composition is located a t 80 per cent total acid and 25 per cent nitric acid in the anhydrous acid is extended horizontally t o reference line 0, and thus locates a point representative of the specific heat of the mixture. Extending a line through this point and a point on temperature scale N corresponding to 68" F. (100" - 32"), we read the change in enthalpy on scale M as 32 B. t. u. per pound of solution. The relative enthalpy of the mixture, therefore, a t 100" F. is -108 +32 B. t. u. or -76 B. t. u. per pound of solution. The smallest scale possible should be used in reading the temperature difference since this leads to the greatest accuracy in the erithalpy readings. Following is an example of the use of the charts in the calculation of heat balances commonly encountered in the preparation of mixed acids for nitration: A mixed acid containing
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INDUSTRIAL AND ENGINEERING CHEMISTRY
August, 1942
ENTHALPY
RELATIVE
TO
BASE
- BT.U.
PER
POUND OF
,
SOLUTION
, , , , , , , , ( ,3
I l I l c 1 r i r r n I l l l l l l l i i l l l l l i l l f 7 l ~ ? ~I , I T T T , , T T 0
-
5
I I I I , I / , I / I I , I , / , , , / I 1 , I , / , , / , / , , / /
N
M
8
e
8m
B
ii
N
(II
0
0
0
t
PER CENT
BY
WEIGHT OF
TOTAL
ACID
FIGURE 1. ENTHALPY CHANGEWITH TEMPERATURE FOR THE SYSTEM NITRIC ACID-SULFURIC ACID-WATER
D n
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Vol. 34, No. 8
INDUSTRIAL AND ENGINEERING CHEMISTRY
100
90
80
70
60 LL
0 50
40
B
30
20
IO
0 0
20
IO
30
40
PER CENT HNO,
50
60
I N ANHYDROUS
70
80
90
ACID
FIGURE 2. RELATIVEENTHALPY OF NITRICACID-SULFURIC ACID-WATER MIXTURES(STAKDARD STATE, PURECOMPONENTS AT 32 F.) O
'
55 per cent sulfuric acid, 10 per cent nitric acid, and 35 per cent water at 90" F. is required for a nitration reaction. This is to be prepared by mixing the requisite amounts of 30 per cent nitric acid a t 70" F., 85 per cent sulfuric acid at 70" F., and pure water at 60" F. Heat will be liberated in this mixing and enough must be removed so that the temperature of the final mixture will not be above 90" F. The quantity of heat to be removed may be calculated as follows: The total relative enthalpies are obtained by adding the values as read from Figures 1 and 2: Relative
Mixture
?t?%'V (Figure 2)
30% HNOa a t 70' F. Water a t 60' F. 857' HzSOa a t 70' F. Mi&d acid a t 90' F.
-- 100 131
- 600
Enthalpy Change 32' t o T o F. (Figure 1) 28.1 28.0 316.5 0.6
Relative Enthalpy -31.9 28.0 -83.5 -100.5
100 pounds of mixed acid will require 33.3 pounds of 30 per cent nitric acid, 64.7 pounds of 85 per cent sulfuric acid, and 2.0 pounds of water. The heat balance is as follows:
Enthalpy of entering materials: 30% " 0 8 at 70" F. = 33 3 (-31.9) = -1063 B. t. u. 85% WZSO~ at 70" F, = 64 7 (-83 5) = -5400 lOO%H,O at 60" E'. = 2 ( 28.0) = 56 -6407 B. t. U. Enthalpy of mixed acid: Mixed acid at 90" F. = 100 (-100.6) Heat to be removed Per 100 lb. mixed acid Per lb. mixed acid
= -10,050 B. t. u.
3643 B. t. u. 36.43 B. t. u.
