Showing papers on "Solvent published in 1975"

Proton-Transfer Reactions

Abstract: 1 Proton acids, Lewis acids, hard acids, soft acids and superacids.- 2 Gas-phase proton-transfer equilibria.- 3 Proton-transfer and the solvation of ammonium ions.- 4 Participation of hydroxylic solvent molecules.- 5 Hydrogen bonding and proton-transfer reactions in non-aqueous solvents.- 6 Fast and slow proton-transfer reactions in solution.- 7 The Bronsted relation significance of the exponent.- 8 Substrate isotope effects.- 9 Solvent isotope effects.- 10 Tunnelling in hydrogen transfer reactions.- 11 Neighbouring group participation.- 12 Proton-transfer in enzymatic catalysis.- 13 Heterogeneous proton-transfer reactions.

The exchange capacities of kaolinite and the preparation of homoionic clays

Abstract: The concepts of cation and anion exchange capacity, as applied to kaolinite, are critically examined. By attention to experimental detail it was possible to obtain reproducible measurements of ion uptake. Contrary to classical ideas the new data show no evidence for any definite cation exchange capacity. The cation uptake depends upon the cation chosen, the electrolyte concentration and pH, and on whether the experiment is done from aqueous or 95%-ethanol solvent. Apparent “capacities” as high as 25 μequiv/g of kaolinite were obtained with Ca 2+ and Cs + from the nonaqueous solvent and as low as 12 μequiv/g of kaolinite with Li + from aqueous solutions. The data suggest complex ion exchange reactions on heterogeneous -SiOH and -A1OH sites. They do not support the simple model of isomorphous substitution charge plus basic edge sites so often assumed in the past.

Process for refining crude glyceride oils by membrane filtration

Abstract: Crude glyceride oils are refined by membrane filtration under pressure in solutions in organic solvents, particularly to separate phosphatides, which may also be refined according to the invention. The solvents are non-acidic, non-hydroxy solvents, e.g., esters, hydrocarbons and halogenated hydrocarbons, particularly in which micelles are formed and the solution is contacted under pressure with a semi-permeable membrane, preferably anisotropic and made from synthetic resin. These pass a permeate fraction of low molecular weight components, eg the glycerides and solvent, and retain a fraction of higher molecular weight, e.g., phosphatide micelles.

Acceleration of DNA renaturation rates

Abstract: The rate of renaturation of DNA may be increased by altering the effective solvent volume available for DNA in solution. Accelerations are demonstrated when neutral and anionic dextran polymers are used to exclude volume in DNA solutions. The logarithm of the DNA renaturation rate constant is shown to be proportional to the concentration of dextran polymer and to be proportional to the intrinsic viscosity of a series of dextran polymers of identical chemical composition. A theory is proposed to account for these results.

Membrane solvent extraction

Abstract: A membrane solvent extraction system is utilized to separate two substantially immiscible liquids and extract a solute through a solvent swollen membrane from one solvent liquid phase to the extracting solvent liquid without direct contact between the liquid phases. The membrane extraction method has advantages over conventional solvent extraction and may be applied as the mechanism in separation, purification, pollutant removal and recovery processes.

Chromatographic Analysis of Hydrocarbons in Marine Sediments and Sea water

Abstract: The low concentration of hydrocarbons anticipated in pollution baseline studies necessitates the development of analytical techniques sensitive at the sub-microgram per kilogram concentration level. The method of analysis developed in this laboratory involves dynamic headspace sampling for volatile hydrocarbon components of the sample, followed by coupled-column liquid chromatography for the non-volatile components. These techniques require minimal sample handling, reducing the risk of sample component loss and/or sample contamination. Volatile sample components are separated from the matrix in a closed system and concentrated on a TENAX-GC packed pre-column, free from large amounts of solvent and ready for GC/GC-MS analysis. Non-volatile compounds, such as the benzpyrenes, may be extracted from large volumes of water and concentrated on a Bondapak C18 packed pre-column for coupled-column liquid chromatographic separation and analysis. Results of the application of these techniques to the analysis of samples from sites of known low level hydrocarbon contamination are presented and discussed.

Temperature, concentration, and molecular weight dependence of the twist elastic constant of cholesteric poly‐γ‐benzyl‐L‐glutamate

Abstract: Aspects of the behavior of the twist elastic modulus K22 of a lyotropic liquid crystal formed by the α‐helical polypeptide poly‐γ‐benzyl‐L‐glutamate of three molecular weights (MW= 300 000, 310 000, and 550 000) in three solvents (dioxane, dichloromethane, and chloroform) were investigated as a function of concentration and temperature. We find that K22 in this system may be made to vary over a wide range by adjustment of solvent and polymer molecular weight. Only a slight concentration dependence of K22 throughout the liquid crystal range was, however, noted. The variations can be at least partially understood in terms of changing macromolecular interactions and recent statistical hard‐rod theoretical treatments of liquid crystal elasticity. The functional form for the temperature dependence of the order parameter was also determined for the system through the clearing point.

Method of preparing microcapsules

Abstract: Void-containing microcapsules are prepared by a method featuring gellation of an organic polymer with the simultaneous precipitation of an organic liquid non-solvent. The method involves the preparation of a solution containing an organic polymer, a good solvent for the polymer and an organic liquid non-solvent which is miscible with the polymer solvent. The solution is then atomized into a bath containing a liquid which is miscible with the good polymer solvent but which is immiscible with the organic liquid non-solvent. The bath liquid extracts out the good polymer solvent, causing gellation of polymer around discrete droplets of the organic liquid non-solvent, which simultaneously precipitates out of the solution as the good polymer solvent is extracted, thereby producing microcapsules having encapsulated therein the non-solvent. The organic liquid non-solvent can then be removed as by evaporation to provide void-containing microcapsules. These void-containing microcapsules may be employed as opacifying agents. In addition to producing void-containing microcapsules, this method can be utilized to produce microcapsules in which pigments are entrapped in the voids or the polymeric walls of the microcapsules or in which certain non-solvents which serve a secondary function remain entrapped in the microcapsules. Such non-solvents include, for instance, vitamins, minerals, biocides, perfumes, chemical reactants, fertilizers, and the like.

Solvent structure. The use of internal pressure and cohesive energy density to examine contributions to solvent-solvent interactions

Abstract: Internal pressures, (∂U/∂V)T, have been obtained at 25° for the solvents dimethyl sulphoxide, propylene carbonate, formamide, dimethylformamide, acetonitrile, methanol and hexamethyl-phosphoramide by measurement of the thermal pressure coefficients. Data in the literature suggest that values of the internal pressure and the cohesive energy density, (ΔU/Vm), are similar for a non-polar solvent. The observed divergence of the two properties in the polar solvents under investigation is discussed in terms of the nature of the solvent-solvent interactions.

Protein-water interaction studied by solvent 1H, 2H, and 17O magnetic relaxation.

Abstract: Previous studies of the magnetic field dependence of the magnetic relaxation rate of solvent protons in protein solutions have indicated that this dependence (called relaxation dispersion) is related to the rotational Brownian motion of the solute proteins. In particular, the dispersion of the longitudinal (spin-lattice) relaxation rate 1/T1 shows a monotonic decrease with increasing field, with an inflection point corresponding to a proton Larmor frequency which is inversely proportional to the orientational relaxation time of the protein. We have now compared the relaxation dispersion of solvent 1H, 2H, and 17O In aqueous solutions of lysozyme (molecular weight 14,700) and 1H and 2H in solutions of hemocyanin (molecular weight 14,7 00) and 1H and 2H in solutions of hemocyanin (molecular weight 9 x 10(6)). The main experimental observation is that the dispersion of the relaxation rates of the three solvent nuclei in lysozyme solutions, normalized to their respective rates in pure water, is essentially the same. This is also true for 1H and 2H relaxation in hemocyanin solutions. These results confirm that entire solvent water molecules, rather than exchanging protons, are involved in the interaction. We have been unable to deduce the correct mechanism to explain the data, but we can eliminate several interaction mechanisms from consideration. For example, all observations combined cannot be explained by a simple two-site model of exchange, in which water molecules are either in sites on the protein with a relaxation rate characteristic of these sites, or else in the bulk solvent (the observed relaxation rate being the weighted average of the two). Also eliminated is the class of models in which the protein molecules induce a preferential partial alignment of neighboring solvent molecules, for example by electrostatic interaction of the electric dipole moments of the water with the electric fields produced by surface charges of the protein molecules. In addition, the idea that relaxation of solvent nuclei is due, in the main, to interactions with protein protons is precluded. Rather, it appears that the protein molecules influence the dynamics of the motion of solvent water molecules in their neighborhood in a manner that imposes on all the solvent molecules a correlation time for their orientational relaxation which equals that of the solute proteins.

Method of extracting useful components from microbial cells

Abstract: Method of extracting a useful component from microbial cells by disrupting microbial cells. Microbial cells are disrupted in one or more stages in a high-pressure multi-stage homogenizer and said disrupted cells are contacted with solvent in one or more remaining stages of the homogenizer to extract a useful component.

Process for the removal of H2 S and CO2 from gaseous streams

Abstract: A cyclic process for the simultaneous removal of hydrogen sulfide and carbon dioxide from a variety of gas streams is disclosed. The gas stream containing the sour gases is contacted with a solution of the Fe (III) chelate of N-(2-hydroxyethyl) ethylene diamine triacetic acid in a CO 2 selective solvent. The hydrogen sulfide is converted to sulfur, the CO 2 is absorbed to produce a purified gas stream, and the Fe (III) chelate is converted to the Fe (II) chelate. The process includes sulfur removal and simultaneous regeneration of the solvent and the Fe (III) chelate.

Inclusion Complexes of Unsaturated Fatty Acids with Amylose and Cyclodextrin

Abstract: The best method for determination of the composition of amylose-fatty acid complexes comprises acid hydrolysis, followed by solvent exrtaction of the fatty acids. The fatty acid content of a cyclodextrin complex can be directly titrated with alcoholic alkali. The complexes were prepared in aqueous solution, and some influences of reaction parameters were observed. A higher fatty acid concentration resulted in every case in a higher fatty acid content of the complex. By washing the complex with dioxane or petroleum ether only the fatty acid adsorbed on its surface was removed. By using ethanol the fatty acid could be removed from the complex. The fraction of the fatty acid mixture incorporated into amylose is enriched in saturated fatty acids. The unsaturated fatty acids included into the complexes are practically completely protected against oxidation.

Percutaneous absorption of organic solvents

Abstract: The percutaneous absorption of 8 chlorinated solvents were studied. The ex-perimental method consisted of the application of the solvent to the abdominal mouse skin and quantitating its absorption through the skin by its presence in whole body and its appearance in expiration. Determination of the solvent in tissues and expiration was carried out by gas chromatographic methods.There was a great diversity of ability among solvents to penetrate the mouse skin. Dichloromethane was absorbed to an amount which was 53 times as large as the amount of tetrachloroethyene. Among tested solvents, those which had the highest solubility in water showed the greatest absorption rate, while those having the lowest solubility in water gave the smallest absorption rate from skin. The linear relationship between the absorption rate from skin and the solubility in water was found: in case of X ?? 16, Y=30.8+2.13X, r=0.87; in case of X ?? 16, Y= -52.8+6.59X, r=1.00; where Y is the percutaneous absorption rate (nM/min/cm2 of skin) and X is the solubility in water of solvent (mM at 25°C).

Thermochemical investigations of nearly idela binary solvents. II. Standard heats of solution in systems of nonspecific interactions

Abstract: Standard heats of solution at 25°C are reported for squalane in mixtures ofn-heptane + iso-octane and in binary mixtures of chloroform, carbon tetrachloride, and cyclohexane; for cyclohexane in chloroform + carbon tetrachloride; and for chloroform in carbon tetrachloride + cyclohexane. General equations based on simple mixing models are developed for the excess thermodynamic properties of a solute at infinite dilution in a binary solvent. For the systems studied, mixing equations based on volume fractions give better agreement than those based on mole fractions, and the agreement is further improved by the use of weighting factors based on the properties of the solute + solvent binary systems.

Multiple solvent heavy oil recovery method

Abstract: Petroleum may be recovered from viscous petroleum-containing formations including tar sand deposits by injecting into the formation a multiple-component solvent for the petroleum. At least one solvent component is gaseous at the temperature and pressure of the petroleum reservoir such as carbon dioxide, methane, ethane, propane, butane or pentane and at least one component is liquid at the reservoir conditions, such as hexane and higher molecular weight aliphatic or aromatic hydrocarbons. The multiple solvent is preferably introduced under sufficient pressure that it is substantially all in the liquid phase. Recovery of petroleum and solvent may be from the same well as is used for injection or from a remotely located well. When the pressure in a portion of the formation contacted by the solvents is reduced below the vapor pressure of the gaseous solvent, it vaporizes to provide drive energy for oil production. The liquid components dissolve in the petroleum and reduce the petroleum viscosity.

Carrier gas vaporized solvent oil recovery method

Abstract: Viscous petroleum may be recovered from viscous petroleum-containing formations including tar sand deposits by injecting into the formation a gaseous mixture of a carrier gas and a solvent which is liquid at reservoir conditions, such as pentane, hexane, heptane, octane, carbon disulfide, etc., and mixtures thereof. The gaseous mixture is formed by contacting a normally liquid solvent with a carrier gas such as nitrogen and introducing the carrier gas having solvent vaporized therein into the formation. Recovery of petroleum and solvent may be from the same well as is used for injection or from a remotely located well. The carrier gas and/or solvent may be heated prior to injection to increase solvency rate and vapor pressure. In throughput operations, the gaseous solvent mixture may be followed by water, hot water or steam to displace the residual solvent from the formation.

Salting-out of alkanols by inorganic electrolytes

Abstract: The free energies, entropies and enthalpies associated with the salting-out of alkanols (mainly butanol) by eight inorganic electrolytes have been determined at 20°C. The results are discussed in terms of the scaled particle theory (in the case of 1 : 1 electrolytes) and the thermodynamic theory of McDevit and Long. It is concluded that alternative approaches to the treatment of salting-out would be desirable. A simple, semi-empirical method for the calculation of salting coefficients is proposed. It is based on the effect which the electrolyte has on the surface tension of the solvent (water) and is found to be relatively successful for many systems.

Intramolecular excimer formation in 1,3‐bis(N‐carbazolyl)propane: Solvent viscosity effects

Abstract: Rate constants for intramolecular excimer formation and dissociation in 1,3‐bis(N‐carbozolyl)propane have been measured in a number of different solvents using time resolved fluorescence decay techniques. It is found that within homologous series of solvents both rate constants decrease progressively with increasing viscosity and obey a relationship originating with the concept of free volume requirements for intramolecular conformational change. Among a group of chemically and structurally different solvents both rate constants are observed to vary randomly with the macroscopic solvent viscosity indicating that other solvent properties are also important. The results are discussed in terms of a qualitative model in which the microstructure of the solvent shell surround the interacting chromophores, as determined by the degree of solvation, ultimately determines the ease with which this intramolecular photophysical process can occur.

Theory of hydrophobic bonding. III. Method for the calculation of the hydrophobic interaction based on liquid state perturbation theory and a simple liquid model

Abstract: In a previous paper, the solubility of liquid hydrocarbons at a pressure of 1 atm in water was correlated with the surface area of the solvent cavity that accommodates the hydrocarbon molecule. In this study, the authors calculate the solubility of gaseous hydrocarbons in water and develop a method to calculate the hydrophobic interactions between hydrocarbon molecules and between hydrocarbon side chains of molecules. The method is based on the first-order perturbation theory of liquid mixtures, and uses a computer-calculated solvent cavity surface area to define solute size. (28 refs.)

Combined multiple solvent and thermal heavy oil recovery

Abstract: Petroleum may be recovered from viscous petroleum-containing formations including tar sand deposits by a process involving injecting into the formation a multiple-component solvent for the petroleum and a thermal fluid. At least one solvent component is gaseous at the temperature and pressure of the petroleum reservoir such as carbon dioxide, methane, ethane, propane, butane or pentane, and at least one component is liquid at the reservoir conditions, such as hexane and higher molecular weight aliphatic hydrocarbons or aromatic hydrocarbons such as benzene. The multiple solvent injection is continued with no production until the pressure is from 50 to 250% above the vapor pressure of the solvent, at which pressure the solvent mixture is substantially all in the liquid phase. Recovery of petroleum and solvent is from a remotely located well by reducing the pressure in the portion of the formation contacted by the solvents to a value from 5 to 100% above the vapor pressure of the gaseous solvent. A fluid heated to a temperature above the boiling point of the solvent, such as steam, is then injected into the same well as was used for solvent injection. The heated fluid raises the temperaure of the solvent on contact therewith, causing vaporization of the gaseous component, which gaseous solvent expands to force viscous petroleum with liquid solvent dissolved therein toward the production well. In formations having oil saturation greater than 50%, this oil saturation should first be reduced to a value below 50% to prevent plugging.