INDUSTRIAL AND ENGINEERING CHEMISTRY
June, 1923
621
Equations for Vapor Pressures and Latent Heats of Vapori zati on of Naphthalene, Anthracene, Phenanthrene, and Anthraquinone’ By 0.A. Nelson and C. E. Senseman B U R E A U OP CHEMISTRY, WASHINGTON, D. C.
decrease of the latent heat ESULTS obtained Only calculated vapor pressures and latent heats of vaporization of vaporization with the infrom experiments on of naphthalene, anthracene, phenanthrene, and anthraquinone are crease in temperature or vapor-pressure deconsidered here. This work is an outgrowth of a study of the obpressure. By plotting the terminations of naphthaserued vapor pressures of these compounds. The calculations were results thus obtained on lene, anthracene, phenmade by applying the Clapeyron equation of state. coijrdinate paper, the equaanthrene, and anthraquiThe derivation of the equation is discussed. tion for L is readily deternone and curves showing The entropy of vaporization of the same compounds was also calmined from the curve. graphically the change of culated and the conclusion that all form normal liquids was reached. The latent heat of vaporvapor pressure with a The observed and calculated vapor pressures given for each comization decreased appreciachangc, of temperature, but pound agree closely. bly in all cases except with with no attempt to derive anthraquinone. A slight equations for the curves obtained, have been reported.2 Dodge3 has called atten- decrease was observed with this compound also, but not tion to the fact that the vapor pressures of these or similar enough to warrant taking the change into account when decompounds can be determined with a fair degree of ac- riving the vapor pressure equation. The latent heat of vaporization may be expressed as a funccuracy by relations described by Diihring and by Ramsay and 6T cT2. , . . . .etc., Young, and has pointed out how a knowledge of these relations tion of the temperature, or L = a would be of value to industrial chemists who might need to where a, b, c, etc., are constants, and T again represents abestimate vapor pressures to within approximately 5 per cent solute temperature. In every compound studied, L could be represented by a straight-line equation, over the temperaof the true value. bT. It should A still more accurate calculation of vapor pressures can be tures or pressures investigated, or L = a made by applying the ClapeyTon equation of state. Ac- be pointed out that the latent heat of vaporization is a linear cordingly, some vapor pressures of the compounds named function of the temperature only for short temperature inhave been calculated and the results compared with the values tervals. I n general, if L were plotted against temperature the curve would become steeper with the rise in temperature, previously observed. The change of the vapor pressure of any substance with a until a t the critical temperature it would be almost perchange of temperature is shown exactly by the Clapeyron pendicular to the temperature axis. For this reason the equations given for L will not hold much above the highest temequation developed thermodynamically. peratures recorded and cannot be used for calculating critical temperatures or pressures. Substituting this value for L in Equation 2 and solving for dP - is the change in vapor pressure with change in temper- P, the Clapeyron equation becomes dT logP = c - -ature; L is latent heat of vaporization; and V and v are the (4) 4.5795T 1.9885 l o g ” volumes occupied by one mol of the vapor and liquid, reThe entropy of vaporization of these compounds has also spectively, a t the temperature T (absolute) a t which the been calculated for the purpose of determining whether or vaporization takes place. This was accomplished by Over short ranges of temperatures the heat of vaporization not they form normal liquids. dividing the latent heat of vaporization by the product RT, may be considered constant. This, of course, is not strictly T being the temperature (absolute) a t which the concentratrue, inasmuch as L becomes zero a t the critical temperature, tion of the vapors was 0.00507 mol per liter, as suggested by which in most cases is approximately 1.5 times the absolute Hildebra~id.~The entropy of vaporization a t this concenboiling point of the liquid. (V-v) is almost equal to V, since tration, according to Hildebrand, should be about 13.7 for is very small compared with V. Making use of these apevery normal liquid. proximations, and considering P V = N R T to hold over small NAPHTHALENE temperature ranges ( N = t h e number of mols, in this case L=17841.24-14.88 T being I ) , Equation 1 may be written: L = 13.7 Entropy of vaporization a t 413 (absolute) = dP L RT
R
+
+
+
a
O
(2)
d T = RT2 P
Log
Integrating, solving for L, and changing to log,,,, Equation 2 becomes
L
= (log Pz
(y?;)
- log Pi) TIT2 -
(3)
Applying this equatioh, it is thus possible to calculate the Presented before the Division of Dye Chemistry a t the 64th Meeting of the American Chemical Society, Pittsburgh, Pa., September 4 to 8, 1922. 2 THIS JOURNAL, 16 (1922), 58. 8 I b i d . , 14 (1922), 569.
fi
= 30.9387
3895.67
- -T - 7.4779 log ‘I’ TABLEIs
TEMP.
c.
100 115 125 140 155 170
----PRESSURE-Observed Calculated Mm. Mm. 18.5 18.4 35.0 35.3 51.8 52.3 88.7 87.7 144.4 144.1 226.1 226.5
TEMP. ‘C. 180 190 200 210 220
...
----PRESSURE-Observed Calculated Mm. Mm. 299.1 299.7 390.2 390.8 502.1 503.5 637.2 636.7 797.9 794.5
...
...
‘ J . A m . Chem. SOC.,37 (19151, 970. 6 All calculations for this and the following tables were made by the use of a 5-place logarithm table and a slide rule.
INDUSTRIAL A N D ENGINEERING CHEMISTRY ANTHRACENE
TABLE 111
L = 18624 - 8.0 ’I’ Entropy of vaporization at 518” (absolute) = Log p = 20.7103
- 4066.8- 4.0223 log T
’
L = 13.7 RT
Temp. ’ C.
230 250 270 280
----PRESSURE---. Observed Mm.
58.3 104.4 173.6 220.0
Temp. C.
Observed Mm.
220 240 260 280
Calculated Mm.
Temp.
42 7 76.1 129.5 211.0
300 320 340 345
42.6 76.0 129.1 211.0
---PRESSURE--Observed Calculated Mm. Mm.
O C .
232 0 502 9 732 9 799.5
-
474r 7*3 -
LogP=3351.3
RT
Temp.
c.
= 14.4
310 320 330 340
6.7893 log ‘ I ‘
WORKS, CHICAGO, ILL.
Distillate c c.
Corresponding Acetyl Value
500 700 900 1300
124.5 133.5 142.5 147.5
Distillate cc.
April 2, 1923. Assoc. Official Agr. Chem., Methods, 1920, 250.
(E1 - +) + 2.16967
PRESSVRE----. Observed Calculated Mm. Mm. 186.0 186.1 7 -
232.0 287.5 355.0
232.7 288.8 355.9
Pmp. C. 350 360 370 380
---
PRESSURE---
Observed Mm.
Calculated Mm.
435.5 531.7 643.7 763.4
435.6 529.3 640.3 769.4
J. A m . Chem. S a c , 44 (1922),392.
Crude Rubber Committee Plans Work
,
A meeting of the Crude Rubber Committee of the Rubber Division, AMERICAN CHEMICAL SOCIETY, was held a t the Chemists’ Club in New York City, M a y 8, 1923. All the active members were present and the work of the committee was planned and organized. As a compound t o test for variation of rate of cure, the puregum stock-100 rubber and 10 sulfur-was adopted. For the evaluation of quality a formula containing 3 per cent sulfur, 30 per cent zinc oxide t o 100 of rubber, and accelerated with “hex,” was tentatively decided upon. Mr. Rose will take up the development of a breakdown and a swelling test. Mr. Van Valkenburgh will work on viscosity determinations, and determine the value of the zinc oxide-“hex” stock for test purposes. Mr. Sanderson will investigate the matter of selecting the most significant physical measurements for cure criteria, using the pure-gum test formula. Mr. Cranor will undertake to determine the relation between variation of different lots as shown in the pure gum mix, compared with the action of the same rubbers in certain practical accelerated mixmgs. The committee expects t o have a definite report for the fall meeting of the AMERICAN CHEMICAL SOCIETY.
Chemistry in the East Indies
These figures indicated, no definite end-point, and to see if one could be reached, another sample mas run with the following results:
2
276.2 425.1 629 4 756 4
The foregoing would indicate the impossibility of obtaining definite results by this method. The committee next tried the Andre-Cook3 method with much better agreement than either of the two previous mentioned. Six laboratories collaborating obtained results varying from 142.5 to 148.2, with an average of 145.46. a
1 Received
276.1 424.0 629.4 757.0
-
TABLE IV
While making a study of the methods in use for the determination of the acetyl value in conjunction with the Committee on the Analysis of Commercial Fats and Oils, some data were collected that may be of general interest. All the results are from determinations made on samples of the same lot of oil. The first methods to be tried out were those of the Association of Official Agricultural Chemists.2 Separating the acetic acid by filtration, four laboratories collaborating obtained results varying from 137.7 to 163.2. Separating the acetic acid by distillation, six laboratories collaborating obtained results varying from 108.4 to 165.4. The results by the distillation method were so erratic that further work was done in this laboratory to throw some light on the trouble. The method was followed in detail up to the point of distillation, where the distillate was collected in fractions, the distillation being carried much farther than usual to note results. Below is given the total volume of distillate, together with the corresponding acetyl value calculated from the total acid collected at each cut.
Corresponding Acetyl Value
290 310 330 340
PRESSURE--Observed Calculated Mm. Mm.
RT
By Jesse R. Powell
Distillate cc.
58.7 103.7 173.2 219.7
---
Entropy of vaporization a t 551O (absolute) = L = 14.0
Notes on the Determination of the Acetyl Value’ ARMOUR SOAP
Temp. ‘C.
L = 15347
231.1 499 8 733 0 800.3
PHENAKTHREPU‘E L=21740.5-13.5 T Entropy of vaporization a t 517’ (absolute) = Log @ = 29.5477
Calculated Mm.
ANTHRAQUINONE
TABLEI1 ---PRESSURE---
Vol. 15, KO. 6
Corresponding Acetyl Value
The Royal Academy of Sciences of Amsterdam has recently prepared a series of papers (in English) summarizing the development of various fields of science in the East Indies, one of which is “A Review of Chemical Investigations in the Dutch East Indies.” This is a brief and comprehensive digest of the contributions which have been made by Dutch chemists of the East Indies upon problems of pharmaceutical, agricultural, and industrial chemistry of t h a t region. Special mention is made of cinchona cultivation, the sugar industry, rubber, tea,. coffee, and tobacco cultivation, the production of essential oils, and phytochemical investigations. A supply of these papers has been sent to the National Research Council, Copies may be obtained (without charge) by addressing E. W. Washburn, Chairman, Division of Chemistry and Chemical Technology, National Research Council, 1701 Massachusetts Ave.. Washington, D. C.
