Conductometric titrations of polyprotic acids in nonaqueous mixed solvents.  Effects of temperature and composition of the solvent mixture

The problem of proton mobility has been considered in H2O–CH3OH, H2O–D2O, and H2O–H2O2 solvents from the current viewpoint of the mechanism of proton mobility for aqueous solutions. Mixed solvents are more complicated in that one must consider the relative basicity and acidity of the species competing for the protons. It is concluded that for dilute solutions of HClO4, where water is replaced by hydrogen peroxide, the decrease in equivalent conductance relative to that of KCl in the same solvent mixture is due to the partial elimination of the proton transfer process.For highly acidic non-aqueous solvents of high dielectric constants such as HF, HCN, and HCOOH, the problem of the weakness of the usual "strong" acids of aqueous solution makes a direct determination of the limiting equivalent conductances difficult. In the case of anhydrous hydrogen fluoride the available experimental evidence indicates that the limiting conductance of the lyonium ion is approximately the same as that of the potassium ion but the lyate ion has a higher limiting conductance than other stable anions.The higher proton mobility in ice leads one to expect that hydrogen-bonded systems may be found where the conductivity may approach that of electronic semiconductors.

Download Full-text

The Interaction of Plasticizers and Polymers

Rubber Chemistry and Technology ◽

10.5254/1.3546778 ◽

1945 ◽

Vol 18 (4) ◽

pp. 790-802

Author(s):

Elizabeth M. Frith

Keyword(s):

Linear Function ◽

General Problem ◽

Mixed Solvent ◽

Polymer Solutions ◽

Mixed Solvents ◽

Previous Theory ◽

Effect Of Solvent ◽

Dilute Polymer Solutions ◽

Effects Of Temperature ◽

Comparative Measure

Abstract The general problem of plasticizer compatibility is discussed, and it is suggested that a comparative measure of compatibility can be obtained from experiments which measure polymer-plasticizer interactions (w). Experiments are described which measure the viscosity of dilute polymer solutions in suitable mixed solvents containing the plasticizer in question. The slope of the ηsp/c−c curve is shown to be related to the equilibrium extent of swelling of the polymer in the pure plasticizer and, in general, the slope of the curve is a good comparative measure of the plasticizer's compatibility. The effects of temperature and composition of the mixed solvent are also discussed. The experiments are considered in the light of a previous theory of the effect of solvent on the ηsp/c ratio: the results do not support the suggested view that the slope of the ηsp/c−c curve is a simple linear function of w/kT.

Download Full-text

Characterization of Synthesized Sodium Carboxymethyl Cellulose with Variation of Solvent Mixture and Alkali Concentration

Open Access Macedonian Journal of Medical Sciences ◽

10.3889/oamjms.2019.524 ◽

2019 ◽

Vol 7 (22) ◽

pp. 3878-3881

Author(s):

Henny Sri Wahyuni ◽

Sri Yuliasmi ◽

Hanifah Siti Aisyah ◽

Devi Riati

Keyword(s):

Carboxymethyl Cellulose ◽

Mixed Solvents ◽

Solvent Mixture ◽

Degree Of Substitution ◽

Water Soluble ◽

Synthesis Process ◽

Alkali Concentration ◽

Infrared Analysis ◽

Coarse Powder ◽

Organoleptic Test

BACKGROUND: CMC is one of the water-soluble polysaccharide derivatives obtained from cellulose. Alkalization and carboxymethylation process will influence the quality of the CMC. The use of a combination of mixed solvents and varying alkali concentrations in the synthesis process of CMC needs to be studied so that CMC can be synthesized with the proper characteristics. AIM: This study was conducted to determine the characteristics of carboxymethyl cellulose synthesized using various solvents and NaOH concentrations. METHODS: Carboxymethyl cellulose (CMC) was synthesized using solvent mixture, namely isopropanol: isobutanol (30: 70) and isopropanol:ethanol (50: 50) with varied concentration of NaOH of 5%, 10%, 15%, 20%, 25%, respectively. Synthesized CMC was characterized by an organoleptic test, pH, infrared analysis, and degree of substitution (DS). RESULTS: The result showed that characteristics of synthesized CMC were different from one another. The organoleptic test showed that synthesized CMC uses isopropanol: isobutanol (30: 70) was coarse powder, odourless and tasteless, ivory until burlywood along with increasing NaOH concentration; while the synthesized CMC with isopropanol: ethanol (50: 50) was a colourless, odourless, tasteless and fine powder. The pH of synthesized CMC was neutral. Infrared profile of synthesized CMC indicated the existence of carboxyl functional groups in 1600-1640 cm-1 region. The degree of substitution value of formula II-5, II-10, II-15, II-20, II-25, IE-5, IE-10, IE-15, IE-20, and IE-25 were 0.885;0.757; 0.685; 0.592; 0.575; 0.611; 0.906; 0.603; 0.671; 0.751, respectively. CONCLUSION: Characteristics of CMC vary depending on the type of solvent mixture and NaOH concentrations used in synthesis. The more polarity of a solvent mixture the more colourless and higher DS value of synthesized CMC. On the other hand, the more alkali concentration in synthesis CMC the more colour and higher DS value was acquired.

Download Full-text

Formation of 2D and 3D multi-tori mesostructures via crystallization-driven self-assembly

Science Advances ◽

10.1126/sciadv.aaz7301 ◽

2020 ◽

Vol 6 (16) ◽

pp. eaaz7301

Author(s):

Gerald Guerin ◽

Menandro Cruz ◽

Qing Yu

Keyword(s):

Self Assembly ◽

Mixed Solvents ◽

Three Dimensional ◽

Solvent Mixture ◽

Second Step ◽

Spherical Shells ◽

Topological Constraints ◽

3D Objects ◽

Multistep Process ◽

2D And 3D

The fabrication of three-dimensional (3D) objects by polymer self-assembly in solution is extremely challenging. Here, multi-tori mesostructures were obtained from the crystallization-driven self-assembly of a coil-crystalline block copolymer (BCP) in mixed solvents. The formation of these structures follows a multistep process. First, the BCP self-assembles into amorphous micrometer-large vesicles. Then, the BCP confined in these mesosized vesicles crystallizes. This second step leads to the formation of objects with shapes ranging from closed 3D multi-tori spherical shells to 2D toroid mesh monolayers, depending on the solvent mixture composition. This approach demonstrates how topological constraints induced by the specific interactions between coil-crystalline BCP and solvents can be used to prepare mesostructures of complex morphologies.

Download Full-text

Effects of temperature and solvent composition on conductometric titrations in nonaqueous mixed solvents

Analytical Chemistry ◽

10.1021/ac00172a009 ◽

1988 ◽

Vol 60 (21) ◽

pp. 2358-2364 ◽

Cited By ~ 14

Author(s):

Giancarlo. Franchini ◽

Carlo. Preti ◽

Lorenzo. Tassi ◽

Giuseppe. Tosi

Keyword(s):

Mixed Solvents ◽

Solvent Composition ◽

Effects Of Temperature

Download Full-text

Application of mixed solvents for elution of organophosphate pesticides extracted from raw propolis by matrix solid-phase dispersion and analysis by GC-MS

Chemical Papers ◽

10.2478/s11696-014-0600-4 ◽

2014 ◽

Vol 68 (11) ◽

Cited By ~ 8

Author(s):

Kati Medina-Dzul ◽

David Muñoz-Rodríguez ◽

Yolanda Moguel-Ordoñez ◽

Cristian Carrera-Figueiras

Keyword(s):

Solid Phase ◽

Mixed Solvents ◽

Solvent Mixture ◽

Binary Solvent ◽

Solvent Mixtures ◽

Organophosphate Pesticides ◽

Experimental Conditions ◽

Matrix Solid Phase Dispersion ◽

Phase Dispersion ◽

Relative Standard

AbstractThe excessive application of organophosphate pesticides (OPPs) in crop fields close to hives and its application in beekeeping practices are potential sources of contamination of propolis. Pesticides were extracted from raw propolis by matrix solid-phase dispersion. Because of the complex chemical composition of propolis, binary solvent mixtures based on acetonitrile and a relatively non-polar solvent in different proportions were tested for the selective elution of OPPs. The effect of mixed solvents on clean-up was evaluated by GC-MS and the main interfering compounds co-eluted with pesticides were identified. In addition, three volumes of the solvent mixture and the volume of the sample were evaluated in an experimental factorial design. The final experimental conditions were 1 mL of dissolved propolis and 8 mL of acetonitrile/dichloromethane (g4 r = 25: 75). Mean recoveries ranged from 55 % to 96 % (relative standard deviation < 8 %) with an inter-day precision lower than 24 %. The proposed method was applied to the analysis of real samples obtained from local beekeepers.

Download Full-text

Mixed Solvent-Lauric Acid Solvent-Exchange Induced In Situ Forming Gel

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.819.195 ◽

2019 ◽

Vol 819 ◽

pp. 195-201

Author(s):

Takorn Chantadee ◽

Wichai Santimaleeworagun ◽

Yaowaruk Phorom ◽

Thawatchai Phaechamud

Keyword(s):

Surface Tension ◽

Contact Angle ◽

Lauric Acid ◽

Mixed Solvent ◽

Mixed Solvents ◽

Antimicrobial Activities ◽

Solvent Mixture ◽

High Ratio ◽

Solvent Exchange

Designing lauric acid (L) solvent-exchange induced in situ forming gel (ISG) was conducted in this study by using mixed solvents (N-methyl pyrrolidone (NMP), 2-pyrrolidone (PYR) and dimethyl sulfoxide (DMSO) at different ratios. The pH, density, viscosity, matrix formation, contact angle/surface tension and antimicrobial activities of 50% w/w L in mixed solvents were determined. The pH and density of solvent decreased apparently with L addition. More amount of PYR in the solvent mixture increased the density and viscosity. High viscous manner of PYR resulted in the high surface tension and contact angle. The solvent mixture of NMP/PYR promoted a higher contact angle than the other mixed solvent systems. L in DMSO, PYR or solvent mixture with high ratio of DMSO or PYR transformed into matrix-like rapidly while those in NMP or high ratio of NMP had slower matrix formation after exposure to aqueous fluid. NMP and PYR showed antimicrobial activities effectively against all test microbes while L matrix retarded their activities. The mixed solvent concept is interesting to use for designing ISG comprising L as matrix former to prolong the drug release.

Download Full-text