222 P 7 (7
6
J. Chem. Eng. Data 1985, 30, 222-224
density, g cms period of oscillation standard deviation deviation between calculated and experimental Values, om3 mol-'
RogWry No. Methanol, 67-56-1; heptane, 142-82-5; ethyl acetate, 141-78-6 butyraldehyde, 123-72-8; IsobutyraMehyde, 78-84-2.
(5) Goates, J. R.; Otts, J. B.; Moellmer, J. F. J . Chem. Thennodyn. 1977, 9 , 249. (6) Takenaka, M.: Tanaka, R.; Murakaml, S. J . Chem. 7Ywmodyn. 1980, 12, 649. (7) Riddlck, J. A.; Bunger, E. 8. "Organic Solvents. Physicel Propertles and Methods of Purlflcatlon"; Wiley-Intersclence: New York, 1970. (8) Davles, 0. L.; Goldsmith, P. L. "StatlstlcalMethods In Research and Productkn"; k f n e r Publlshlng Co.: New York, 1972. (9) Mlkhall, S. 2.; Klmel. W. R. J. Ct". Eng. Deta 1961, 8 , 533. (10) Groller, J. P. E.; Ballet, D.; Vlallard, A.'J. Chem. 7 7 " d y n . 1974, 6, 895.
Llterature Clted (1) Eng, R.; Sandler, S. 1. J . Chem. Eng. Data 1984, 29, 158. (2) Shsaly, 0. S.; SaMJbr. S. I.J. Chem. Thennodyn., In press. (3) Wllhelm, E.; Qroller. J. P. E.: Karbalal Ghasseml, M. H. Monatsh. Chem. 1978, 109, 369. (4) Qroller, J. P. E.; Karbalal Ghasseml, M. H.: Inglese, A. rnt. Data Ser., Ser. 6 1977, QukleHne 2c.
Recelved for revlew July 9, 1984. Accepted September 15. 1984. The equipment used h thls work was purchased wlth funds provided by a National Science Foundatlon Grant (No. CPE 8305153) to the Unlverslty of Delaware. N.C.P. Is pleased to acknowledge the Ananclal support that he received as a Postdoctoral Fellow from the Department of Chemlcal Englneerlng at the University of Delaware.
Excess Enthalpies of Blnary Mixtures of 2,4-Dimethylpentane with n-Hexane, n-Heptane, n-Octane, and n-Dodecanet Salah E. M. Hamam,$ M. K. Kumaran,§ Mngan Zhang,Il and George C. Benson" Division of Chemlstry, National Research Council of Canade, Ottawa, Ontario, Canada K1A OR6
Cakrkmtrk mea sur^ of excem enthalpies are reported for Unary mMures of 2,rl-dlmahylp.ntsne wlth n-hexane, n-heptrme,noctane, and n-dodeeane at 208.15 K. The rewlk for the mlxtures contalnlng n-hexane and noctane are much lower than prevlous edlmates of excess enthalples obtalned from vapor-llquld equillkla.
The effect of chain branching on the excess thermodynamic properties of binary mixtures has been investigated previously in our laboratory by measuring excess enthalpies for mixtures of nheptane (I), noctene (2),and ndodecane (3) with each of the five hexane isomers. The present paper reports the results of similar measurements for mixtures of a branched isomer of n-heptane, 2,Mlmethylpentane (2,4-DMP), with the n-alkanes: n-hexane, n-heptane, n-octane, and ndodecane.
Table I. Sources, Purities, and Densities, p(T = 298.15 K), of the Component Liquids source and . purity .
2,4-dimethylpentane n-hexane
Phillips Petroleum Co., Research Grade, 99.72 m o l % Phillips Petroleum Co., Research Grade, 99.95 m o l % Phillips Petroleum Co., Pure Grade, >99 m o l % Aldrich Chemical Co., Gold Label, >99 m o l % Phillips Petroleum Co., Pure Grade, >99 m o l %
n-heptane n-octane n-dodecane
obsd
668.44 668.32 654.92 654.84 679.67 679.46 698.61 698.62 745.23 745.18
all cases, x is the mole fraction of 2,4-DMP. The parameters of the smoothing equation HmE/(Jmol-') = x(1 - x ) [ l
Experhentat Sectlon
p l & g m-') lit. (5)
liquid
- k(1 - 2x)I-l
c h,(l m
- 2x)C'
j=1
Excess molar enthalpies, HmE, were determined at 298.15
(1)
K in a modified LKB flow microcalorimeter. Details of the equipment and its operation have been degcrlbed previously ( 7 , 4). For most of the measurements the error In the determiis estimated to be less than 0.5%. However, it nation of HmE (
