Shape Of Isotherms Research Articles

Effects of salt concentration and spreading amounts on surface pressures of layers of latex particles grafted to polymer chains at interfaces between air and aqueous salt solutions

Polystyrene (PS) latex particles grafted to diacetone acrylamide chains were spread in layers at the air-aqueous interfaces of NaCl solutions. Their surface pressures were investigated as a function of the NaCl concentration in the water phase, at different initial surface concentrations of PS latex particles. At low initial surface concentrations of PS latex particles, the isotherms of the monolayers measured during compression-expansion cycles exhibited slightly a negative hysteresis, i.e. a decrease in surface pressure as the number of compression-expansion cycles increased, irrespective of the NaCl concentration. The isotherm obtained upon expansion was almost the same as the compression isotherm for three repeated compression-expansion cycles. On the other hand, at high initial concentrations of latex particles, in which the surface area per particle could reach much smaller values upon compression, the compression-expansion isotherms clearly showed a plateau region. In this region, PS latex particles were laterally close packed at the interface, irrespective of NaCl concentration as well as the number of cycles. The isotherm shape was strongly dependent on NaCl concentration; negative hysteresis was observed when NaCl concentrations were lower than 0.001 M and higher than 0.15 M, except for the plateau region in the expansion cycles. The isotherm recorded using a 0.025 M NaCl subphase exhibited negative hysteresis below the plateau region.

Impact of climatic factors on the release of E-β-caryophyllene from alginate beads

Description of the subject. Alginate beads that release semiochemical compounds are interesting biological control devices used to attract the natural enemies of aphids in infested crops. Little information, however, is available about the impact of climatic factors on the release of semiochemicals from this diffusive system. Objectives. The objective of this scoping study was to investigate the impact of temperature, relative humidity and wind speed, on the release of E-β-caryophyllene from alginate beads. Method. The impact of the three climatic factors on the release of E-β-caryophyllene from alginate beads was evaluated using a Box-Behnken experimental design and a laboratory scale volatile collection system. The influence of relative humidity on bead water content and size, with and without this semiochemical, was also investigated using a gravimetric method and an easy-to-use photographic device, respectively. Results. The results showed that an increase in temperature caused a significant increase in the E-β-caryophyllene release rate. Neither relative humidity nor airflow, however, had a significant effect on the release of this semiochemical when relative humidity and wind speed ranged from 33% to 75% and from 6.61 x 10-4 m·s-1 to 2.05 x 10-2 m·s-1, respectively. The isotherm curves obtained were characteristic of food products and biopolymer materials. The isotherm shapes were not modified by the incorporation of the semiochemical into alginate beads, and showed an important increase in water content when relative humidity values exceeded 85%. Fortunately, this water content increase did not affect bead size, which facilitates the calculation of E-β-caryophyllene release. Conclusions. The present study shows for the first time the impact of the three main climatic factors on the release of E-β-caryophyllene from alginate beads. It allows learning more about how these biological control devices operate in order to optimize future field trials.

Solvothermal and electrochemical synthetic method of HKUST-1 and its methane storage capacity

A comparison synthetic strategy of Metal-Organic Frameworks, namely, Hongkong University of Techhnology-1 {HKUST-1[Cu3(BTC)]2} (BTC = 1,3,5-benzene-tri-carboxylate) through solvothermal and electrochemical method in ethanol:water (1:1) has been conducted. The obtained material was analyzed using powder X-ray diffraction, Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), Thermo-Gravimetric Analysis (TGA) and Surface Area Analysis (SAA). While the voltage in the electrochemical method are varied, ranging from 12 to 15 Volt. The results show that at 15 V the texture of the material has the best degree of crystallinity and comparable with solvothermal product. This indicated from XRD data and supported by the SEM image to view the morphology. The thermal stability of the synthesized compounds is up to 320 °C. The shape of the nitrogen sorption isotherm of the compound corresponds to type I of the IUPAC adsorption isotherm classification for microporous materials with BET surface area of 629.2 and 324.3 m2/g (for solvothermal and electrochemical product respectively) and promising for gas storage application. Herein, the methane storage capacities of these compounds are also tested.

Assessment of Technical and Economic Feasibility of Activated Charcoal Removal of Organic Matter from Different Streams of Grey Water Through Study of Adsorption Isotherms

The feasibility of household level treatment of grey water with activated charcoal was performed using laboratory batch adsorption testing on locally available charcoal media. The study results indicated that the potential for removal of organic matter was significantly high for the high pH cloth wash water compared to the low pH kitchen wastewater which also contained non-adsorbed organics. The addition of ash considerably improved the removal and projected life length of adsorption media for kitchen wastewater treatment. The adsorption isotherms obtained were all modeled adequately using the Freundlich isotherm while the isotherm shapes display different types of adsorption for the different streams of grey water because of the heterogeneous nature of the adsorbates in grey water. The replacement life length of activated charcoal for single drum household level treatment ranged between 7 and 15 months. For family daily flow rates up to 400 lit/day, the replacement costs of a single drum charcoal per cubic meter of grey water treated were calculated to be below the current tariff levels for acquiring water in cities in Swaziland. A considerable part of the grey water pollutant can be removed through pretreatment by sorption alone such as by filtration through sand or other cheap media before adsorption. For complete household level treatment of grey water, a three-step treatment consisting of sand pre-filtration, activated charcoal adsorption and sand post-filtration are recommended.

Effects of Resin I on Asphaltene Adsorption onto Nanoparticles: A Novel Method for Obtaining Asphaltenes/Resin Isotherms

The main objective of this study is to investigate the effect of resin I on the adsorption behavior of n-C7 asphaltenes onto silica and hematite nanoparticles. It is worthwhile to mention, for the first time, that competitive adsorption of n-C7 asphaltene and resin I over nanoparticles is reported. Indeed, a novel method based on thermogravimetric analysis (TGA) and softening point (SP) measurements was used for the simultaneously construction of adsorption isotherms of n-C7 asphaltenes and resins. The adsorption experiments were conducted in the batch mode at different n-C7 asphaltene to resin I (A:R) ratios of 7:3, 1:1, and 3:7 and different concentrations of the asphaltene–resin mixture from 500 mg/L to 5000 mg/L. The adsorption isotherms were described by the solid–liquid equilibrium (SLE) model. The results showed different shapes of the adsorption isotherms according to the A:R ratio. However, the nanoparticles become more selective for asphaltene at a high asphaltene/resin ratio. In addition, the a...

Combined influence of pore size distribution and surface hydrophilicity on the water adsorption characteristics of micro- and mesoporous silica

Adsorption processes are ubiquitous in nature as well as of great technological importance for gas separation, purification, storage and thermally driven heat pumps. This has led to a strong interest in the fundamental mechanisms governing adsorption phenomena and their exploitation to tailor adsorption systems for specific applications. In particular, the adsorption of water on porous silica exhibits remarkable properties due to the strong polarity of the adsorbate and moderate hydrophilicity of the adsorbent. It is generally accepted that the adsorption of water vapor on porous silica depends upon the concentration of surface silanols and the pore size. In fact, materials with ordered mesopores and a well-defined pore size have been used as model systems to demonstrate that water adsorption occurs predominantly through capillary condensation. While the pore surface chemistry is modified to become more hydrophilic after filling of the pores in these materials, the overall shape of the water adsorption isotherm (Type V) is not significantly affected in subsequent adsorption measurements. The present contribution shows that conservation of the isotherm shape is a unique phenomenon related to ordered mesopores but doesn't apply to materials with a more complex pore structure. For materials with wider pore size distributions including micropores, a synergistic effect of surface hydroxylation and pore size leads to a dramatic change in the water adsorption isotherm after the first adsorption/desorption cycle. In fact, we demonstrate that the water cycling capacity at relative pressures below the onset of capillary condensation increases significantly in these systems. These results contribute to a fundamental understanding of water adsorption in complex systems and have important implications in applications such as adsorption heat pumps where a large water cycling capacity in a specific relative pressure window is required.

Adsorption of copper by ordinary and southern chernozems from solutions of different salts

The aim of this work was to study the effect of the attendant anions and particle-size distribution on the adsorption of copper by chernozems of Rostov region (Russia). The samples of soil in the natural cationic form were treated with solutions of copper nitrates, acetates, chlorides, and sulfates at a soil: solution ratio of 1:10. The concentrations of the initial copper solutions varied in the range from 0.05 to 1mM/L. The suspensions were shaken for 1h, left to settle for a further 24h and then filtered. The metal concentrations in the filtrates were determined by atomic absorption spectrometry. The concentrations of the adsorbed copper cations were calculated from the difference between the metal concentrations in the initial and equilibrium solutions. The effect of the attendant anions Cl−, SO42−, Ac−, and NO3− and particle size distribution on the adsorption of copper by chernozems of the Rostov region has been studied under laboratory conditions. The shape of the adsorption isotherms varies depending on the attendant anion and is described by the Henry, Freundlich, and Langmuir equations. The adsorption of copper by the soil is accompanied by the acidification of equilibrium solutions (рНeq): 0.53≤ΔрНeq≤2.06, which depends on the attendant anion. The highest value of ΔpHeq corresponds to the adsorption of Cu2+ from the copper sulfate solution and its lowest value, from the copper chloride solution. The effect of the attendant anions decreases in the series: Cu(Ac)2>CuCl2>Cu(NO3)2 >>CuSO4. In the southern chernozems, a close correlation is observed between the maximum copper adsorption and the content of clay and silt (R=0.99). No correlation is found between the values of adsorption constants and particle size distribution, which is related to the changes in the chemistry and mineralogy of the soils studied.

Deformation of Microporous Carbon during Adsorption of Nitrogen, Argon, Carbon Dioxide, and Water Studied by in Situ Dilatometry.

Adsorption-induced deformation of a monolithic, synthetic carbon of clearly distinguishable micro- and mesoporosity was analyzed by in situ dilatometry with N2 (77 K), Ar (77 K), CO2 (273 K), and H2O (298 K). A characteristic nonmonotonic shape of the strain isotherm showing contraction of the sample at initial micropore adsorption followed by expansion toward completion of micropore filling was found for all adsorbates. However, the extent of contraction and expansion varied significantly with the adsorbate type. The deformation differences observed were compared with the density ratio of the adsorbates within the micropores and the respective unconfined fluids. In particular, CO2 caused the least contraction of the sample, while in parallel adsorbed CO2 molecules were predicted to be considerably compacted inside carbon micropores compared to bulk liquid CO2. On the contrary, the packing of H2O molecules within carbon micropores is less dense than in the bulk liquid and adsorption of H2O produced the most pronounced contraction. N2 and Ar, both exhibiting essentially the same densities in adsorbed and bulk liquid phase, induced very similar deformation of the sample. These findings support theoretical predictions, which correlate adsorption-induced deformation and packing of molecules adsorbed in micropores. Additionally for the first time, we demonstrated with the N2 strain isotherm the existence of two nonmonotonic stages of subsequent contraction and expansion in the regions of micropore and mesopore filling. This characteristic behavior is expected for any micro- and mesoporous material.

Adsorption of argon on pure silica MEL. Volumetric experiments and grand canonical Monte Carlo simulations

The adsorption isotherm of argon on the zeolite MFI at liquid nitrogen temperature exhibits a sub-step at high loading before saturation that, in spite of much theoretical and experimental effort, is still lacking a definitive microscopic interpretation. In this work, we try to get insight into this peculiar behaviour by investigating the adsorption of argon on MEL, a zeolite that is structurally very similar to the MFI. First, we performed volumetric experiments that confirm that the adsorption of argon on MEL presents the same qualitative behaviour as on the MFI, again a sub-step appearing at high loading before saturation. Subsequently, the microscopic origin of this behaviour was investigated by means of molecular simulation. The simulations indicate that, for loads lower than that of the experimental sub-step, argon atoms can accommodate at low energy positions within the zeolite pores, whereas, above this point, some reordering of the adsorbate is needed to host further argon atoms. Moreover, the flexibility of the zeolite can have a significant impact on the shape of the adsorption isotherm, although the magnitude of this change depends on the zeolite model potential.

Optimizing isothermal titration calorimetry protocols for the study of 1:1 binding: Keeping it simple

BackgroundSuccessful ITC experiments require conversion of cell reagent (titrand M) to product and production or consumption of heat. These conditions are quantified for 1:1 binding, M+X ⇔ MX. MethodsNonlinear least squares is used in error-propagation mode to predict the precisions with which the key quantities — binding constant K, reaction enthalpy ΔH°, and stoichiometry number n — can be estimated over a wide range of the dimensionless quantity that governs isotherm shape, c=K[M]0. The measurement precision σq is estimated from analysis of water–water blanks. ResultsWhen the product conversion exceeds 90%, the parameter relative standard errors are proportional to σq/qtot, where the total heat qtot ≈ ΔH° [M]0V0. Specifically, σK/K×qtot/σq ≈ 25 for c=10−3−10, ≈ 11 c1/3 for c=10−104. For c>1, n and ΔH° are more precise than K; this holds also at smaller c for the product n×ΔH° and for ΔH° when n can be held fixed. Use of as few as 10 titrant injections can outperform the customary 20–40 while also improving productivity. ConclusionThese principles are illustrated in experiment design using the program ITC-PLANNER15. General significanceSimple quantitative guidelines replace the “c rules” that have dominated the literature for decades. This article is part of a Special Issue entitled Microcalorimetry in the BioSciences — Principles and Applications, edited by Fadi Bou-Abdallah.

Enantioselective sorption of the chiral fungicide metalaxyl on soil from non-racemic aqueous solutions: Environmental implications

Mechanisms governing the enantioselectivity of the processes that determine the behavior of chiral pollutants in the environment need to be better understood. Understanding these mechanisms should help improve predictions of the hazards and risks chiral compounds can pose to people and the environment. We report the results of batch sorption experiments indicating that the sorption of the chiral fungicide metalaxyl on soil from non-racemic initial solutions was enantioselective. While from a racemic initial solution the two enantiomers of metalaxyl were sorbed on the soil to the same extent, increasing the fraction of R-enantiomer in the initial solution led to enhanced sorption of this enantiomer and to reduced sorption of the S-enantiomer. Considering the shape of the sorption isotherms (S-type) and the sorption behavior of model sorbents, we attributed this effect to molecular interactions between metalaxyl enantiomer species at the sorbed state, where R-R metalaxyl interactions appeared to be more favorable than R–S metalaxyl interactions. We discuss important environmental implications of the proposed mechanism, such as those related to the fact that the biological degradation of metalaxyl is known to be an enantioselective process that can yield non-racemic residues in soils shortly after application of the fungicide as a racemic mixture.

Experimental and Theoretical Investigations of CO 2 Sorption by a 3D In‐MOF with Multiple 1D Channels

The CO2 sorption capacity of the 3D In-MOF (Et2NH2)[In(2,6-NDC)2]·2H2O·DEF (I) (where 2,6-NDC is 2,6-naphthalenedicarboxylate and DEF is N,N-diethylformamide) was investigated. The solvent-free I contains three distinct types of 1D micropores with different shapes and pore dimensions. The evacuated I sorbed 297.2 cm3 g–1 (13.3 mmol g–1) of CO2 at 196 K, 72.2 cm3 g–1 (3.22 mmol g–1) at 273 K, and 39.8 cm3 g–1 (1.78 mmol g–1) at 298 K. The difference between the uptake at 196 K and those at 273 and 298 K is relatively large. The shapes of the sorption isotherms are also dramatically different. At 196 K, the adsorption–desorption isotherms are S-shaped without significant hysteretic behavior between the adsorption and desorption branches. On the contrary, the adsorption isotherms measured at 273 and 298 K fit well with the Langmuir–Freundlich equation. The low-surface-coverage isosteric heat (Qst) of CO2 adsorption by I is 19.6 kJ mol–1. Detailed estimations of the adsorption sites for CO2 were then performed by DFT calculations. The calculated binding energies were typically dependent on the dimension of the micropores when nonbonding (van der Waals) interactions were considered; the larger the micropore dimensions, the smaller the calculated binding energy. In addition, not only the framework CH···OCO contacts for Ch3 but also the counter-cation CH···OCO contacts for Ch1 and Ch2 were found to be important.

Water vapor adsorption characteristics of starch−albumen powder and rheological behavior of its paste

ABSTRACT This paper concerns the water vapor adsorption properties of starch-albumen powder (SAP), as a new product with many potential food processing applications. The adsorption data were generated at some practical storage temperatures (27, 35 and 40 °C) and water activities, a w (0.11–0.86) using gravimetric method. The data were fitted to some isotherm models (GAB, Peleg, DLP and BET). The values of some thermodynamic parameters based on the Clausius–Clapeyron equation were also calculated. The rheological behavior of SAP paste was also studied at 20, 30, 45 and 60 °C. SAP was found to have type II isotherm shape and is highly hygroscopic. The adsorption data were better fitted by Peleg and DLP models ( r 2 =0.987–0.999). Monolayer moisture capacity ranged between 4.9 and 6.8 g/100 g solid. The water vapor sorption process in SAP is thermodynamically non-spontaneous and enthalpy-driven. SAP paste showed a characteristic shear-thinning behavior. Activation energy of flow ( E a ) was found to be 31.63 kJ/mol.

Adsorption of wood extractives and model compounds onto bentonite

The adsorption of wood extractives and representative model compounds into two different forms of bentonite was studied. The colloidal dispersion showed limited solubility which affected the shape of the adsorption isotherm. Modelling of the adsorption isotherms showed excellent fits with Freundlich and BET isotherm models indicating that multilayer adsorption with cooperative binding was occurring. The wood extractives were found to have greater affinity with the bentonite surface than the model compounds. Bentonite B was found to be a better adsorbent than bentonite A due to the differences in exchangeable cations present and its greater swelling capacity and surface area. The addition of ethanol during the preparation of the colloidal dispersions, as done by previous researchers when studying adsorption of the oleic acid, triolein and abietic acid, appears to reduce the affinity and capacity of the adsorption onto bentonite.

Evaluation study of cobalt(II) and strontium(II) sorption–desorption behavior for selection of soil remediation technology

Sorption–desorption properties of cobalt(II) and strontium(II) ions were studied using a soil sample from the vicinity of the Serbian radioactive waste processing and interim storage facilities. The mobility of the cations in the soil was evaluated and compared with the intention to facilitate the selection of optimal remediation strategy in case of accidental soil contamination with radioactive cobalt-60 and strontium-90 isotopes. A systematic sorption study was performed through a series of batch experiments at different aging times, cation concentrations and pH. Kinetics experiments revealed that sorbed amounts of cobalt(II) continuously increased with contact time until quasi-equilibrium was reached, while initial fast strontium(II) sorption was followed by a desorption step. Based on the shapes of the sorption isotherms and calculated sorption parameters, it was concluded that cobalt(II) sorbed more selectively and strongly than strontium(II). Sequential extraction showed that, regardless of the initial content of contaminants in the soil and the aging time, high amounts of both cations were bonded to relatively mobile fractions: strontium(II) in the exchangeable, while cobalt(II) in the carbonate and ferromanganese oxide fraction. Strontium(II) was readily desorbed in acidic, calcium(II) and ethylenediaminetetraacetic acid-containing media, whereas complexing agents such as citric and tartaric acids at low pH were more effective reagents for cobalt(II) desorption. The results from the present study indicate that chemical extraction can be considered as remediation option for strontium(II)- and cobalt(II)-contaminated soil.

Desorption of Exchangeable Cations at Adsorption of Lead Ions by Chernozem in the Presence of Attendant Anions

The effect of Cl–, Ac‾ and NO3‾ anions on the adsorption of Pb cations by an ordinary chernozem and desorption of exchangeable cations in the soil-solution system has been assessed under model laboratory conditions. It has been shown that the attendant anions affect the shape of the adsorption isotherms, which are described by the Langmuir equation. The greatest influence on the affinity constant of Pb with soil has anion Ac‾. It has been found that the uptake of the Pb cations by chernozem from solutions of different salts is accompanied by the displacement of the exchangeable cations to the solution in the following order: Ca2+ > Mg2+ > Na+ > K+. The sum of the displaced exchangeable cations in most cases exceeds the amount of the adsorbed metal cations. The content of Pb cations desorbed by the ammonium acetate buffer solution (pH 4.8) makes up 6-39% of the total Pb adsorbed cations. According to the effect of the anions on the displacing capacity of cations for Pb the following series are formed: Cl¯ > Ac‾ > NO3¯.

Influence of high pressures on CH4, CO2 and H2S solubility in polyethylene: Experimental and molecular simulation approaches for pure gas and gas mixtures. Modelling of the sorption isotherms

The sorption of methane, carbon dioxide and hydrogen sulphide in polyethylene (PE) was investigated. Data were obtained in a large range of pressures from both experiments and molecular simulation. Monte Carlo (MC) simulations in the osmotic ensemble were used to predict gas concentrations in the amorphous polymer phase. An ad hoc constraint in the osmotic simulations was used to mimic the effect of the crystalline phase. The results obtained from MC simulation compared favourably to experimental results and data from literature. Different sorption mechanisms were evidenced in the low to middle gas pressure range as a function of the gas nature. However, the decrease of gas solubility was evidenced at high pressure. It was assigned to a hydrostatic effect and the bulk modulus of the PE amorphous phase was determined. A simple model allowing the accurate description of gas solubility from low to high gas pressure range was proposed. It was shown to accurately describe the different sorption isotherm shapes obtained for PE and the characteristic parameters of the model were determined for each gas.

The interaction mechanism between lipopeptide (daptomycin) and polyamidoamine (PAMAM) dendrimers

The interaction mechanism of lipopeptide antibiotic daptomycin and polyamidoamine (PAMAM) dendrimers was studied using fluorescence spectroscopy. The fluorescence changes observed are associated with daptomycin-dendrimer interactions. The binding isotherms were constructed by plotting the fluorescence difference at 460 nm from kynurenine (Kyn-13) of daptomycin in the presence and absence of dendrimer. A one-site and two-site binding model were quantitatively generated to estimate binding capacity and affinity constants from the isotherms. The shape of the binding isotherm and the dependence of the estimated capacity constants on dendrimer sizes and solvent pH values provide meaningful insight into the mechanism of interactions. A one-site binding model adequately describes the binding isotherm obtained under a variety of experimental conditions with dendrimers of various sizes in the optimal binding pH region 3.5 to 4.5. Comparing the pH-dependent binding capacity with the ionization profiles of daptomycin and dendrimer, the ionized aspartic acid residue (Asp-9) of daptomycin primarily interact with PAMAM cationic surface amine.

Effect of the presence of pyrite traces on silver behavior in natural porous media

In order to better understand the fate of the toxic element Ag(I), sorption of Ag(I) was studied from batch experiments, at different pHs (2–8) and at 298K. A pure quartz sand (99.999% SiO2) and “natural” quartz sand (99% SiO2, and traces of Fe, Al, Mn (hydr)oxides, of clays and of pyrite) were used as sorbents. The Ag(I) sorption behavior depends strongly on pH with isotherm shapes characteristic of Langmuir-type relationship for initial Ag concentration [Ag(I)], range between 5.0×10−7 and 1.0×10−3M. Even if the Ag (I) sorption capacity on pure quartz sand is very low compared to the natural quartz sands, its affinity is rather high. From speciation calculations, several sites were proposed: at pHi 4, 6 and 8, the first surface site is assumed to be due to iron (hydr)oxides while the second surface site is attributed to silanols. At pHi 2, sorption of Ag(I) was assumed to be on two surface sites of iron (hydr)oxides and a third surface site on silanol groups. Even if the sand is mainly composed of silica, the trace minerals play an important role in sorption capacity compared to silica. The conditional surface complexation constants of Ag(I) depend on pH. On the other hand, it is shown that the Ag speciation depends strongly on the history of “natural” quartz sand due to initial applied treatment, little rinsing or longer washing. In the presence of low amount of pyrite, strong complexes between Ag(I) and sulfur compounds such as thiosulfates due to oxidative dissolution of pyrite are formed what decreases Ag sorption capability. SEM–EDS analyses highlighted the surface complexation–precipitation of Ag2S and Ag(0) colloids which confirmed the important role of pyrite on Ag(I) speciation.

Modeling of Excess Molar Volumes of [Difurylmethane + (Acetonitrile or Propionitrile or Benzonitrile)] Binary Mixtures Using the Prigogine – Flory – Patterson Theory

The recently reported experimental excess molar volume data for {difuryl methane + (acetonitrile or benzonitrile or propionitrile)} binary mixtures as a function of composition at T = 298.15 K under atmospheric pressure, have been used to test the applicability of Prigogine-Flory-Patterson theory. Analysis of each of the three contributions to the experimental excess molar volume vis. the interactional, the free volume and the characteristic pressure terms, show that the interactional and the free volume contributions were negative for all three {difuryl methane + (acetonitrile or benzonitrile or propionitrile)} binary mixtures. The characteristic pressure contribution was negative for {difuryl methane + (acetonitrile or propionitrile)} and positive for (difuryl methane + benzonitrile). The relatively large magnitude of the interactional contribution which arises from dipole-dipole interactions between difurylmethane and the nitrile molecule determined the overall experimental shape of the excess molar volume isotherms for {difuryl methane + (acetonitrile or benzonitrile or propionitrile)} binary mixtures. The correlation between the theoretical and experimental excess molar volumes data was satisfactory for each of the three binary systems.