IAVDV S T R I d L SA'D ESGINEERING CHEMISTRY
1106
difference would also increase as the pore radius decreases. The experimental results seem to bear out this inference. Thus it appears that the calculated difference in pore radii of very fine pores may be dependent either upon the surface tension values of the liquid used or upon the adhesion values, of liquid against the solid constituting the pore wall, or perhaps upon both. In any case it follows that the pressure displacement method is applicable for the measurement of pore radii of capillary tubes only when the radii are greater than about 2 X cm. The method does not appear to be suitable for smaller capillaries. Further study along this line should throw some light on the range of molecular attraction and a t the same time give information relative to the thickness of the adsorbed layers.
'
T'ol. 21, s o . 11
Literature Cited (1) Asahara, J a p a n . J . Chem., 1, 35 (1922). (2) Bartell and Fu. Co!loid Symposium Monograph, Vol. VI1 i.1929), in press. (3) Bartell and Fu, J . Phys. Chem., in press. (4) Bartell and Osterhof, Colloid Symposiiim Monograph, Vol V , 113
(1927). ( 5 ) Bartel! and Sloan, J . Am. Chem. Soc., 51, 1643 (1929). (6) Chaney, Trans. A m . Electrochem. Soc., 36,91 (1929). (7) Chaney, Ray, and St. Johns, IND. ENG.CHEM.,16, 1244 (19231 (8) Edser, Bril. Assocn. Adoancement Sci., 4th Colloid Rept., p 40 (1922). (9) Freundlich, "Colloid Chemistry," p. 46. (10) Hulett and Cude, Bur. Mines, Bull. 1913. (11) Johnson, IND.ENG.CHEM.,20, 904 (1928). (12) Miller, J . Phys. Chem., SO, 1162 (192G). (13) Nellensteyn, C h e n . Weekblud, 22, 291 (1925). (14) Ruff, Schmidt, and Albrich, Z.anorg. allgem. Chem., 148, 313 11023). ( 1 5 ) Waele, de, J . A m , Chem. Soc., 48, 2760 (1926:.
Vapor Pressure and Heat of Vaporization of Diphenyl' John Chipman and S. B. Peltier DEPARTMENT OF CHEMISTRY, GEORGIA SCHOOL OF TECHSOLOGY. ATLANTA, A.:(
HE recent achievement
The vapor pressure of diphenyl has been determined two products were therefore between 162"and 322" C. A n equation is derived which of the large-scale proconsidered of equal purity and duction of diphenyl by should be valid for extrapolation UP to 10 or 15 atmosthe larger sample was used pheres. The vapor density has been determined and throughout the work. The the Federal P h o s p h o r u s Company, Birmingham, Ala., the heat of vaporization calculated. The properties boiling point was determined has taken that substance out of diphenyl are shown to be in accord with those of with a platinum resistance other aromatic hydrocarbons. of the class of laboratory curithermometer which was caliosities and has placed it on the brated on the same day a t the market in carload lots a t a price that should make it available boiling points of naphthalene and benzophenone. The boiling for many purposes. Aside from the preparation of many prom- point of diphenyl was found to be 254.05' C. at 741 mm. ising derivatives, the chief application of diphenyl has been as Correcting this by means of our vapor pressure data, the a material for high-temperature vapor-phase heat transfer. normal boiling point a t 760 mm. is 255.25' * 0.05' C. Here its low vapor pressure and high critical temperature Temperature Measurements give it advantages over steam which are too obvious to require elaboration. Moreover, it has a fairly high heat of A set of short Anschutz thermometers graduated in 0.2" c'. vaporization, high molal heat capacity, and for all practical and each covering a range of about 60" C. was used. The purposes may be considered stable a t high temperatures. entire set was carefully calibrated, a t least four points being For the proper utilization of this new material complete checked on each thermometer. The calibrations were cartables of its physical and thermal properties are greatly to ried out by comparison as follows: 0" to 50' C., Bureau of be desired. It was the object of this investigation to de- Standards certified thermometer; 60' to 120' C., vapor termine a few of its more important characteristics-namely, pressure of water, data of International Critical Tables; its vapor pressure, vapor density, and heat of vaporization. 100" to 200' C., Reichsanstalt certified thermometer, rcIt is also of interest to compare the form of its vapor pressure checked a t steam point; 199" and 255' C., platinum recurve with that of other aromatic hydrocarbons. This phase sistance thermometer; 216.8" and 304.7' C., boiling points of the investigation will be discussed in a later paragraph. of naphthalene and benzophenone a t 741 mm. ; 280" to 332 " C., vapor pressure mercury, data of International Purification of Diphenyl Critical Tables. The adjoining and overlapping ranges were A 3-oound (1.4-kg.) samule of commercial diphenyl sup- in all cases in agreement within 0.1" C. plied b i the Federal-Phosphorus Company was first crystalVapor Pressure Measurements lized from alcohol, then twice fractionally distilled in an allOn the Pyrex still having an efficient fractionating head. The method used was a modification of the isoteniscope second distillation the entire charge distilled over within a method of Smith and Menzies (6). The apparatus was range of 0.5" C., but only the middle portion (300 grams) patterned after that of Mortimer and Murphy ( 4 ) with coming over a t 254.4-254.5' C. a t 745 mm. was retained. slight changes for the sake of greater convenience and range. This distillate, which was of a light straw color, was then A short closed manometer, well boiled out, was used for recrystallized from methanol. The resultant pure white pressures below 100 mm. Long open manometers were used crystals melted sharply a t 69.2' C. to form a colorless liquid. for pressures up to about 2 meters above atmospheric, the h small sample from the Eastnian Kodak Company was pressures being conveniently obtained by means of an orditwice recrystallized-first from alcohol and then from ethernary tire pump. The barometer was checked by direct comand distilled. This product also melted a t 69.2" C. The parison with the Bureau of Standards instruments a t the Atlanta Station of the U. S. Weather Bureau. Meter bars I Received June 21, 1929.
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INDUSTRIAL A N D ENGIYEERING CHEiVISTRY
Sovember, 1929
1107
The data are fitted by the following equation within the limits of experimental error: log P(mm.) = 7.0220
U
was boiled until a large part of it had distilled over into the U; then b y c a r e f u l manipulation of the p r e s ~ r emost of this was returned to the bulb, the pressure being relieved just in time to prevent air from being forced back into the bulb. The temperature was held as nearly constant as possible while a number of readings were made. the bulb being boiled out before each reading. After satisfactory checks had been obtained, the temperature was lowered and an-
0 0
1 4
EU
u l
-
1723/T - 215700/T2
(2)
The general validity and usefulness of this type of equation will be discussed elsewhere. It is sufficient here to note that it is undoubtedly a more accurate means of expressing vapor pressures bhan any other equation of a like number of ternis. An equation of the same form reproduces the I. C. T. data for water within 0.1 per cent over a range from 30 nnn. to 30 atmospheres. It is believed, therefore, that Equation 2 for diphenyl will prove to be not seriously in error u p to 10 or 1.5 atmospheres. Table I1 shows the vapor pressures at rouiid temperatures interpolated and extrapolated by means of the equation. Extrapolated values are given in parentheses.
During each run the liquid in the U was under close observation and control to prevent the return of air into the bulb. Four runs were made-run 1 starting a t atmospheric pressure, runs 2, 3, and 4 starting at approximately 1500, 2700, and 517 mm., respectively. The liquid in runs 2 and 3 was turned slightly yellow by the prolonged heating and the observed pressures below atmospheric deviated slightly froin corresponding values in runs 1 and 4. For these reasons the lower data of runs 2 and 3 were discarded. In other respects the data were quite concordant. The experimental data are presented in Table I. Each point recorded represents the mean of a group of two to five observations.
Isoteniscope for Vapor Pressure Measurements
Table 11-Vapor
Pressures of Diphenyl a t Round Tempera tures TEMPERATURE PRESSURE Lbs. per sq. i i i . Mm. O F. 0.060 0.82 (200) 0.227 (250) 4.35 0.701 17.2 (300) 1.832 54.2 350 4.197 105.3 400 8.638 191.5 450 16.29 000 329.1 28.54 537.8 550 47.01 842.2 600 73.55 1269 (650) 110.1 1851 (700) 158.6 2621 (750) 221.0 ( 600) 3614 4870 6425 8315
TEMPERATURE PRESSURE
c.
( 70) ( 100)
(130) 160 180 200 220 240 260 280 300 320 (340) (360) (380) (400)
Apparently the only data in the literature on the vapor pressure of diphenyl are those of Jaquerod and Wassmer ( 2 ) . These investigators measured the boiling points of naphthalene, diphenyl, and benzophenone under pressures froin 250 to 800 mm. using a hydrogen thermometer. The boiling points of naphthalene and benzophenone have since been adopted as secondary points on the I. C. T. scale. These points are, respectively, 0.28' and 0.46" C. higher than those recorded by Jaquerod and Wassmer. If we assume that their thermometer was correct a t 100" C. we find that the correction to be applied to their data is a linear function of the temperature, and by interpolation the correction a t 254.93' C. is 0.36" C. With this correction their boiling point of diphenyl is 255.29" C., in excellent agreement with the writers' value, 255.25" C. Similarly corrected, all of their data are in fair agreement with those of the writm. Density of Liquid and Vapor
Table I-Vapor K1.s 4 4 4 4 4 4
1 -1 4
1 -1
Pressure of Diphenyl TEMPERPRESSURE PRESSURE RUN ATURE OBSERVEDBY Ea. 2
T E M P E R - P R E S S U R E PRESSTJRE A T U R E O B S E R V E D B Y
[email protected] C. 162.6 172.3
177.7
183.5 191.6 198.75 203.8 211.15 220.05 220.5 229 8 238,2 247.7
'53.7
Mm. 59.5 82.0 96.9 117.8 149.8 185.2
213.8 260.1 328 2
332.7
422,s 516.8 641.9 735.2
Mm. 59.3
82.2 97.9 117.5 150.1 184.8 213.2 260.6 329.5 333.3 421.0 515.7 642.2 734,3
C. 1 2 3
2 2 3 3
2 2 3 3 3 3 3
255.2268, ia 265.3 266.2 275.3 276.1 285.1
285.9 287,5 294.5 303,6 312.1 320.1 322.3
Mm.
Mm.
758.9 822 5 942.0 964.0 1161 1178
758.9 820.0 942.4 960.0 1167 1175 1402 1423
1406 1427 1467 1677 1963 2286 2630
2727
1466 1674 1975 2292 2626 2724
Discussion of the Data
The data were plotted on a large scale, the logarithm of the pressure against the reciprocal of the absolute temperature. The line was smooth and very slightly curved. The slope at the normal boiling point was found to be - d log P I d ( l / T ) = 2653
(1)
In older to ralculate the heat of vaporization froiii vapor pressure data, it is necessary to know the change in volunie when 1 mol of liquid is converted into vapor. This is readily obtained from the densities of the two phases. The vapor density was determined by the well-known Dumas method. The deterininations mere carried out in bulbs of about 230 cr. capacity, heated in a bath of cottonseed oil. The mean of five determinations a t 260" C. and 740 mm. was 3.615 * 0.01 grams per liter. In the short interval between these conditions and the normal boiling point the gas laws may be aswined to hold. The density of the saturated vapor at the boiling point is thus found to be 3.75 * 0.01 grams per liter. The density of the liquid at the boiling point waa found to be Rpprovimately 0.85 gram per cubic centimeter. Heat of Vaporization
The Clapeyron equation, dP/dT = LH/TAV, was used to calculate the heat of vaporization. The value of dP/dT is obtained from the vapor pressure data, or more directly from Equation 1. The molal volumes of vapor and liquid a t the
I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
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boiling point are found to be, respectively, 41.1 * 0.1 and 0.18 liters. Hence the heat of vaporization is 11,470 * 50 calories per mol, or 74.4 * 0.3 calories per gram. Comparison with Other Hydrocarbons
The entropy of vaporization a t the boiling point is 11,470/528.35 = 21.7 calories per degree. The value predicted by the Kistiakowsky equation (1, 3) is 21.23. The observed is therefore 2.3 per cent higher than the predicted value, in good agreement with the behavior of other hydrocarbons. It can also be shown that the form of the vapor pressure curve is in accord with that of other aromatic hydrocarbons. For this purpose it is only necessary to write the approximate vapor pressure equation, valid in the vicinity of the boiling point, obtained directly from Equation 1. This approximate equation is: log P (atm.) = 7.9020 - 2653/T (3)
Vol. 21, No 11
A method for predicting the constants of this equation when the boiling point is known has recently been described ( 1 ) . The equation used for the prediction is log P ( a h . ) = log(82.07Tb) - g Tb log(82.07rb)/T in which the term g Tb log(82.07Tb) gives the slope of the log P versus 1/T curve, Tb is the absolute boiling point, and g (called the “slope factor”) is a constant for a given class of substances. The values of g for benzene, toluene, naphthalene, anthracene, etc., are all in the neighborhood of 1.08. Solving Equations 3 and 4, it is found that the value of g for diphenyl is 1.083. Literature Cited (1) Chipman, J . Phys. Chem., 32, 1528 (1928); 33, 131 (1929). (2) Jaquerod and Wassmer, B o . , 37, 2531 (1904). (3) Kistiakowsky, J . Russ. Phys. Chem. Soc., 63, 256 (1921). (4) Mortimer and Murphy, IND.Ezio. CHEM.,16, 1140 (1923). (5) Smith and Menzies. J . A m . Chem. Soc., 32, 1412 (1910).
The Flow of Pseudoplastic Materials’ R. V. Williamson EXPERIMENTAL STATION. E. I.
DU
PONTDE NEMOURS & COMPANY, WILMINOTON, DEL.
HE practical i m p o r -
Many dispersions do not exhibit a real yield value flocculates which compose the and cannot be molded; yet their flowing properties tance of distinguishing disperse phase.2 The deforare similar in certain respects to the flowing properties plastic flow from vismation and deflocculation of of ideal plastics. These dispersions are called pseudocousflow has becomegenerally the flocculates r e l e a s e e n plastics. recognized in this country as trapped liquid and also perA graphical method for separating the viscous and t h e r e s u l t of the work of mit an orientation of partiplastic resistances of pseudoplastic dispersions into Bingham ( 1 ) . But, as pointed cles in the direction of flow separate measurable quantities serves as a basis for the out by Bingham (2) in his which would not be possible development of a new equation for pseudoplastic flow. recent papers, certain types if the particles were entangled The equation contains three constants. One of these of dispersions do not flow in in flocculates. The net result constants characterizes the viscous properties of accordance with the laws of of these changes is a decrease pseudoplastic dispersions and is called the viscosity either ideal fluids or ideal in resistance t o flow. As the constant. The ratio of the two other constants is a plastics. The flowing properrate of shear becomes higher constant which characterizes the plastic properties t i e s of such dispersions are and higher, the possibility of of dispersions and is referred to as the plasticity consimilar in many respects to producing further changes in stant. The ratio of the plasticity constant to the the flowing properties of ideal the character of the disperse viscosity constant gives a constant which appears to be phase becomes less and less. plastics; therefore we shall rea quantitative measure of that property commonly fer to them as pseudoplasConsequently, the resistance known as false body. to shear of the dispersion aptics. The primary difference The viscosity and plasticity constants are expressed proaches a constant minimum b e t w e e n pseudoplastic flow in the same units; therefore they may be compared in v a l u e . This value will be and ideal plastic flow is the any manner desired. These two constants seem to considered to represent the absence of a real yield value meet the practical demand for a method of quantitareal viscosity of the disperin pseudoplastic flow. tively evaluating as individual properties the viscous Equations for the flow of sion. Any variation of the and plastic properties of dispersions. ideal fluids a n d f o r i d e a l apparent viscosity from the r e a l o r minimum viscosity plastics have been fairly well established, but a satisfactory equation for pseudoplastic flow will be considered to be due to the plastic character of the has not been formulated although several have been proposed dispersion. A graphical method of resolving the power required t o (3, 4, 5, 7, 8, 9, IO). The object of this paper is to present the development of a new equation for pseudoplastic flow and maintain a given rate of flow into the portion characteristic to show some of the practical results that may be obtained of viscous flow and the portion characteristic of plastic flow is given in Figure 1. Curve O A represents a typical rate from its application. of shear-shearing stress curve of a pseudoplastic dispersion.
T
Development of Equation for Pseudoplastic Flow
In the development of this equation, the plastometer will be considered as a miniature colloid mill in which part of the power required to maintain any given rate of flow is used to overcome the viscous resistance of the dispersion and the remainder is used to deform and deflocculate the July 3. 1929. Contribution No. 12 from Experimental I . du Pant de Nemours & Company, Wilmington, Del.
1 Received
Station,
E.
Note-Rate of shear, instead of rate of flow, is plotted against shearing stress because this method of plotting is independent of the instrument used to obtain the Bow-pressure data. For viscous liquids flowing through a capillary viscometer, rate of shear equals V/1 X 4/sr’, where V/1 equals rate of flow in cubic centimeters per second, and I equals radius of capillary in centimeters. The shearing stress in dynes per square centimeter equals 2 Compare McBain’s theory of neutral colloids as solvated micelles capable of aggregation. J . Phys. Chem., 30, 239 (1926). Kraemer and Williamson, J . Rheology, 1, 76 (1929).
