T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
298
Where a thin solution of t h e nitrocellulose was made by dissolving the nitrated material in a solvent such as ether-alcoholl acetone or amyl acetate, the insoluble material settled out from a clear supernatant liquid, indicating t h a t i t could be used in t h e manufacture of collodion and some lacquers. I n these products, however, t h e cost of t h e nitrocellulose itself is of minor importance as compared with the other costs. So there is no advantage in using nitrated corncob cellulose as long as cotton is available.
Vol. 13, No. 4
CONCLUSIONS
It appears t h a t t h e only use for corncob cellulose in t h e explosives industry a t t h e present time is as a carbonaceous absorbent for liquid ingredients, such as nitroglycerin, i n t h e manufacture of dynamite, For t h a t use it must compete with such materials as wood pulp, sawdust, cornmeal, charcoal, peanut hulls, rice hulls, a n d similar materials, all of which have properties which are advantageous for the manufacture of special grades of dynamite.
Some Interpretations of the Ammonia Synthesis Equilibrium1 By R. S. Tour PLANT
ON%
SECTION,
NITRATE DIVISION, ORDNANCE DEPT..AND
THE
T h e extent t o which t h e reaction
'/zNzf
"8
can proceed is a function of t h e temperature, pressure, a n d concentrations of t h e components of t h e system. Thermodynamic considerations lead t o t h e following relation for concentrations a t equilibrium: C N H ~= Kc X (CN~)'/~: X (CH~)*/Z (1) where K, is t h e concentration equilibrium constant. Using partial pressures instead of concentrations, the above may be expressed as: (2) P(NH#) = K, X ( P N 2 ) ' / 2 X ( P H J ' / ~ where ~ ( N H J , (PHJ, ( P N ~ )are partial pressures in atmospheres of t h e respective constituents a n d Kp is t h e pressure equilibrium constant. I n t h e latter form Haber2 gives t h e following equation for the value of Kp as a function of t h e absolute temperature T: 13 :OO logioKp = -- 6.134 (3) 4.571 T
FIXEDNITROGUN RESEARCIi
I,ABORATORY,
WASHINGTON,
D.
c.
decrease of temperature. A reduction of temperature from 500" to 485' C. is as advantageous as a rise in pressure from 100 to 120 atmospheres. (2) Pressure does not increase the ammonia content in direct proportion, but at a decreasing rate with increasing ammonia content.
If a = volume fraction of ammonia in the system at equilibrium, c = volume fraction of inert gases a t equilibrium, r = volume ratio of hydrogen to nitrogen a t equilibrium, P = total pressure in atmospheres,
then by simple transformations m-e may arrive a t the following relation: U
,J/z
= KP (4) (1 - a - C ) Z (1 d2 where K has the same value as K, above. If interested in t h e ammonia content, t h e equilibrium condition may be most simply inspected and calculated, and t h e effect of different variables best noted and determined with t h e help of Formula 4. I n Fig. 1 is given a set of curves showing t h e effect on equilibrium ammonia content of a variation of any one of the conditions involved when t h e others are held a t t h e arbitrary values: T = 7 7 3 " A., P = 100 atmospheres, r = 3, c = 0 . I t is t o be noted from t h e equation and t h e curves t h a t : (1) The effect of temperature is very marked, especially a t the lower temperatures, the ammonia content rapidly increasing with decrease in temperature, although it should be remembered that reaction velocity decreases very rapidly with this 1
Received November 2 6 , 1920.
2
P. Haber, 2 Electuochen., 21 (19151,89.
+
(3) Changes in ratio of hydrogen to nitrogen have but a small effect over a considerable range. The maximum ammonia content is, of course, for the theoretical proportion of 1N2 : 3H1, but a variation to 2N2 : 3H2 (or 0 . 5 NZto 3 H2)involves a reduction of less than 10 per cent of the equilibrium content. (4) The effect of inert diluents is often misunderstood and considered as merely similar to an equal percentage drop in pressure. It should be noted, however, that the pressure of the diluent not only lowers the partial pressures of the reacting gases, but also actually dilutes them as well. T o show this we may write the equilibrium expression in the form:
Apr.,
299
303
T H E J O U R N A L OF I h T D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y a
(1 - a or very closely
- c)2
Vol. 13, N o . 4
a
E
[(I
- a ) ( l -c)
-ac]2
I t will be seen from Equation 5 that the effect of 10 per cent diluents corresponds closely to a 20 per cent drop in pressure. T h e frequent computation a n d solution of t h e e s pression a rX/Z 13200 = KP - where log,,K = -- 6.134 (1 - a - c)2 (1 7)2' 4.571 T
+
is long and tedious, and families of curves are ordinarily confusing. However, if we write t h e closely approsimate expression ( 5 ) in t h e form: log (1-a)z
+ log P +
c)
= 2 log (1.-
13200 -6.134 + r ) 2 + 4.571 T
7=/2
log-
(1
(6)
we may then plot each of t h e terms as a separate single curve with its variable as abscissa. By adding t h e ordinates for any complete set of conditions, we may directly obtain a graphically from t h e cttrve for log
-2.-
(1 - a ) ?
(see Fig. 2).
The figure show diagrammatically t h e set of curves just described. A similar chart a t present in use carries t e n times t h e scale divisions shown in t h e figure and is accurate t o 0.1 per cent NH3. More frequently, however, t h e equilibrium ammonia content is desired when only temperature and pressure are t h e variables, while P is a t t h e theoretical value of 3 . 0 and c = 0. For this case t h e simple nomograph shown in Fig. 3 may be constructed if t h e equilibrium be expressed in t h e form:
logs (1-u)Z
=
logp
+ 2888 -+ const. T
(7)
T h e figure is a reproduction of a chart 12 in. X 42 in., 'which is being used a t present with great satisfaction. It i s hoped t h a t t h e curves and graphical solutions given will prove of value t o laboratories working on t h e problem of ammonia synthesis.
Exports of Naval Stores During the calendar year 1920 domestic exports of naval stores from the United States were valued at $34,545,296, more than three times the figure for 1918, and an increase of 10 per cent over 1919. Annual exports for 1919 and 1920 were as follows :
-
-1920Quantity Value Rosin, kbls. ......... 1,160,385 $19,781,353 Tar, turpentine, and 451,641 53,149 pitch, bbls.. ...... Turpentine (spirits) 14,312,302 gals.. ............ 9 , 1 6 2 , 6 0 7
........
7----1919Quantity 1,209,627
Value $20,433,970
67,258
551 ,703
10,G72,102
10.445.234
TOTAL. $35,545,296 $31,433,997 AVERAGEANNUALEXPORTPRICES O F NAVAL STORLW Tar,Pitch, Spirits of Rosin, and Turpentine. Turpentine, per B bl . per Bbl. per Bbl. Year 1918.. $ 9.70 $7.6: $0.612 1919.. . . . . . . . . . . . . . . . . . . 16.89 8.h 0.879 1920.. . . . . . . . . . . . . . . . . . . 17.05 8.50 1.5&2 December 1920. . . . . . . . . . 12.30 7.04 1.08%
..................
