668 Korean Chem. Eng. Res., 55(5), 668-678 (2017) https://doi.org/10.9713/kcer.2017.55.5.668 PISSN 0304-128X, EISSN 2233-9558 Ultrasonic Speed and Isentropic Compressibility of 2-propanol with Hydrocarbons at 298.15 and 308.15 K Suman Gahlyan, Sweety Verma, Manju Rani* and Sanjeev Maken † Department of Chemistry, Deenbandhu Chhotu Ram University of Science and Technology, Murthal-131 039, India *Department of Chemical Engineering, Deenbandhu Chhotu Ram University of Science and Technology, Murthal-131 039, India (Received 16 May 2017; Received in revised form 15 June 2017; accepted 30 June 2017) Abstract - Intermolecular interactions were studied for binary mixtures of 2-propanol + cyclohexane, n-hexane, ben- zene, toluene, o-, m- and p-xylenes by measuring ultrasonic speeds (u) over the entire range of composition at 298.15 K and 308.15 K. From these results the deviation in ultrasonic speed was calculated. These results were fitted to the Redlich-Kister equation to derive the binary coefficients along with standard deviations between the experimental and calculated data. Acoustic parameters such as excess isentropic compressibility (K s E ), intermolecular free length (L f ) and available volume (V a ) were also derived from ultrasonic speed data and Jacobson’s free length theory. The ultrasonic speed data were correlated by Nomoto’s relation, Van Dael’s mixing relation, impedance dependence relation, and Schaaff’s collision factor theory. Van Dael’s relation gives the best prediction of u in the binary mixtures containing ali- phatic hydrocarbons. The ultrasonic speed data and isentropic compressibility were further analyzed in terms of Jacob- son’s free length theory. Key words: Ultrasonic speed, Oxygenate, 2-Propanol, Hydrocarbon, Jacobson’s free length theory, Graph theoretical approach 1. Introduction Increasing global concern over greenhouse gas emissions has gen- erated much interest in environmentally friendly alternative bio- fuels. Bio-fuels for internal combustion engines as oxygenated com- pounds are also becoming important due to depleting fossil fuel, occasional oil crises and increasing air pollution [1]. Oxygenates produced from renewable sources, including higher alcohol such as propanol, butanol and pentanol, may have acceptable properties as gasoline blend components and could be considered as potential sec- ond generation bio-fuel additives [2]. Propanol can be produced by microbial fermentation of cellulose [3]. This prompted us to study the thermo-physical properties of oxygenate additive with hydrocar- bons that would be of great importance in process engineering design, in formulating motor fuels [4], and also in understanding the nature of intermolecular interactions in these binary mixtures [5-7]. In continuation of earlier work [8-11], ultrasonic speeds of 2-pro- panol + cyclohexane, n-hexane, benzene, toluene, o-, m- and p-xylenes over the entire range of composition at 298.15 K and at 308.15 K are reported in the present paper. The ultrasonic speeds data were cor- related by various correlations like Nomoto’s relation, Van Dael’s mixing relation and impedance dependence relation, and Schaaff’s collision factor theory. The accoustic data were further analyzed in terms of Jacobson’s free length theory (FLT). 2. Experimental 2-1. Chemicals Cyclohexane (Merck 99%) was washed several times with a mix- ture of concentrated nitric acid and concentrated sulfuric acid to nitrate any benzene that may have been present [12]. After repeated washing with NaHCO 3 solution and distilled water, it was fractionally dis- tilled over and dried over 0.3 nm molecular sieves (Merck) in an amber colored bottle for several days before use. n-Hexane (Merck AR grade 99.5%) was treated with concen- trated sulfuric acid, then with a 0.1N solution of potassium perman- ganate in 10% sodium hydroxide [13]. The n-hexane was then washed with water, distilled and dried over type 0.3 nm molecular sieves (Merck). 2-Propanol, benzene, toluene and xylenes were purified as described earlier [14]. The purity of purified samples was checked by measuring densi- ties and refractive indices of the pure compounds, and these agree well with their respective literature values as shown in Table 1 [5,15-23]. The purified samples were also analyzed by gas chromatography for their purity and found to have better than 99.6 wt% (Table 1). 2-2. Apparatus and procedure The ultrasonic speed was measured by using a variable path sin- gle-crystal interferometer (Mittal Enterprises, Model M-81, India). A crystal-controlled high-frequency generator was used to excite the transducer at a frequency of 2 MHz. The interferometer cell was filled with the test liquid, and water was circulated around the measuring cell from a constant temperature bath maintained at (298.15±0.01) K. Details of the ultrasonic speed measurements have been given ear- † To whom correspondence should be addressed. E-mail: sanjeevmakin@gmail.com This is an Open-Access article distributed under the terms of the Creative Com- mons Attribution Non-Commercial License (http://creativecommons.org/licenses/by- nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduc- tion in any medium, provided the original work is properly cited.