Cryoscopic Constant Research Articles

Freeze-Vulnerable Plastic Crystal to Cryogenic Liquid Electrolyte for Lithium Batteries by Deep Freezing-Point Depression.

Low-Tf solvents (Tf = freezing point) are considered and employed for low-temperature lithium-ion battery (LIB) electrolytes to keep electrolytes in the liquid phase at low temperatures. Unfortunately, Tf is synchronized with Tb (boiling point) so low Tf brings Tb down and therefore discourages the thermal stability of electrolytes using low-Tf solvents. In this work, 1) the hot wing of LIB-working temperature by employing a high-Tb (inevitably high-Tf) solvent and 2) the cold wing by using a significant Tf depression is secured. Sulfolane is employed as the high-Tf (therefore, high-Tb) and high-Kf (Kf = cryoscopic constant) solvent since its mesomorphic state between solid and liquid. That abnormally and significantly decreases the enthalpy of fusion, and resultantly grants extremely high Kf at 66.4Km-1. By employing sulfolane with 2m lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), the liquid-phase temperature window down to <-80°C for the cold wing and simultaneously guaranteed its flash point at >+150°C for the hot wing is successfully extended. LIB cells with lithium iron phosphate and lithium metal worked in a good stand with 2m LiTFSI/sulfolane at room temperature, -30°C as an ambient cold, -74°C as a deep cold, and +80°C as a deep hot.

CLUSTERS OF WATER IN THE COMPOSITION OF ANTIFREEZES

Antifreezes based on water eutectics are widely spread in engineering and by crio-preservation of biological objects as well. Salts of inorganic and organic acids, alcohols, glycols, glycol ethers, glycerin, acids, bases, amino- acids, and other chemical compounds are suitable here as supplementary means. Part of these compounds is capable to take part in the formation of H-bonds with water molecules, the others do not form H-bonds (CaCl2), but they are united into crystal-hydrates of CaCl2 · 6 Н2О type. In this case H-bond of water molecules can become the bond of intermolecular-cluster type. It is assumed that basic structural components of liquid water are cyclic penta- (H2O)5 and hexamers (H2O6), built with the participation of the long hydrogen bond and capable of producing the crown effect. Cyclic water clusters - short-range order of water in terms of cavity size and the number of oxygen atoms correspond to crown ethers: 15-crown-5 and 18-crown-6, sodium and calcium ions being absorbed into them. Energy estimation of water and ice (snow) interaction with the components of antifreezes: ethylene- and diethylene glycols, ethylene glycol ethers, hydrogen chloride and ammonia is made. Possibility of solution formation with low freezing temperatures is shown. The analysis of the eutectics and diagrams of water antifreeze fusion based on the salts, alcohols, ethylene glycol, ethylene glycol ethers, hydrogen chloride and ammonia by comparison with an ideal solution of water concerning cryoscopic constant is carried out. It is established that the coefficient K in the equation of linear melting curve y = К·x + в for effective antifreezes, in terms of freezing temperature, exceeds the cryoscopic constant of water, that testifies to the destruction of long-range order of water. Penta- and hexamers of water responsible for short-range order of water pass into the eutectics as monomers or oligomers with the degree of cross linking equal to 2-4. To create effective antifreeze it is important to avoid the destruction of cyclic water clusters. It is desirable, as in the case with ethylene, to have the second component of water antifreeze in a cyclic form too. There is an analogy with naphthenic (cyclic) hydrocarbons of oil, which provide mobility of the condensed state. Promising are antifreezes based on mixtures of inorganic and organic compounds.

Estimating the Contribution of Impurities to the Uncertainty of Metal Fixed-Point Temperatures

The estimation of the uncertainty component attributable to impurities remains a central and important topic of fixed-point research. Various methods are available for this estimation, depending on the extent of the available information. The sum of individual estimates method has considerable appeal where there is adequate knowledge of the sensitivity coefficients for each of the impurity elements and sufficiently low uncertainty regarding their concentrations. The overall maximum estimate (OME) forsakes the behavior of the individual elements by assuming that the cryoscopic constant adequately represents (or is an upper bound for) the sensitivity coefficients of the individual impurities. Validation of these methods using melting and/or freezing curves is recommended to provide confidence. Recent investigations of indium, tin, and zinc fixed points are reported. Glow discharge mass spectrometry was used to determine the impurity concentrations of the metals used to fill the cells. Melting curves were analyzed to derive an experimental overall impurity concentration (assuming that all impurities have a sensitivity coefficient equivalent to that of the cryoscopic constant). The two values (chemical and experimental) for the overall impurity concentrations were then compared. Based on the data obtained, the pragmatic approach of choosing the larger of the chemical and experimentally derived quantities as the best estimate of the influence of impurities on the temperature of the freezing point is suggested rather than relying solely on the chemical analysis and the OME method to derive the uncertainty component attributable to impurities.

Determining the thermodynamic melting parameters of sulfamethoxazole, trimethoprim, urea, nicodin, and their double eutectics by differential scanning calorimetry

The literature data on the thermodynamic melting characteristics of sulfamethoxazole, urea, trimethoprim, and nicodin are analyzed for individual compounds. Their enthalpies and melting points, either individually or in the composition of eutectics, are found by means of DSC. The entropies of fusion and the cryoscopic constants of individual compounds are calculated.

Sulfolane as Solvent for Lithium Battery Electrolytes

The properties and applications in lithium batteries of solutions containing lithium perchlorate dissolved in sulfolane have been studied. Due to the high cryoscopic constant of sulfolane (85 K/mole), the freezing point can be considerably decreased. Also the viscosity can be decreased in a way similar to the idea of mixed carbonate solvents. Viscosity and conductivity obey the mified Walden rule. The addition of sulfolane to carbonate solvents increases their flash point fairly considerably.The capacity of experimental cells containing a LiCoO2 cathode and a carbon anode was ca. 33.33 mAh/g (related to anode material). The internal resistance of the cell increased, and an irreversible charge was observed on discharge curves and described. To some extent, the battery had the capability of a rechargeable one.&#x0D; The use of sulfolane (SL) as a highly polar solvent for electrochemical purposes has been the subject of previous studies [1] – [6]. Its advantages are high permittivity, excedent thermal stability and resistance to strong oxidation potentials. However, there are some disadvantages such as rather high viscosity and correspondingly also low conductivity of salt solutions in this solvent, and a rather high freezing point (+ 28.4 °C).&#x0D; A similar problem arises in ethylene carbonate which exhibits excellent electrochemical properties if solvents with a sufficiently low freezing point and viscosity are added. It is commonly known that the loss of conductivity is not so detrimental , and the freezing point depression can make such mixed solvents useful. Therefore the blends of ethylene carbonate (abbreviated as EC) with other solvents (mostly dimethyl carbonate DMC) are used as solvents for preparation of electrolytes for lithium batteries.&#x0D; The main objective of the present paper is to attempt to suppress the weaknesses of sulfolane by adding a solvent with a sufficiently low freezing point and viscosity in order to facilitate the use of sulfolane for various electrochemical applications in electrochemical science and technology.

Determining the main thermodynamic parameters of caffeine melting by means of DSC

The temperature and enthalpy of the melting of caffeine, which are 235.5 ± 0.1°C and 19.6 ± 0.2 kJ/mol, respectively, are determined by DSC. The melting entropy and the cryoscopic constant of caffeine are calculated.

Advances on the Pharmacology Research of Active Component in Humic Acid

The humic acids in young coal are complex compounds of aromatic-fatty group organic acid with content of functional groups like carboxy, phenolic hydroxyl group, benzoquinonyl, alcohol group , ketone group etc. The pharmacology research of humic acid advanced in slow progress as a result of composition complexity and raw material multiplicity. At first it was analysed that terpene, steroids and other bioactive substances existed in natural humic having effects on antibacterial, antiviral, antitumor and microcirculation improvement. A new way of molecular weight determination for fulvic acid was established by modification of cryoscopic constant which was proved by the detection of capillary electrophoresis and LC-MS then. In terms of Fulvic acid which molecular weight of 300-500, pharmacology of humic acid （FA/HA）- pyrones, humic acid (FA)- catechin, humic acid (FA)-saccharide metabolism of insulin, humic acid (FA)-allantoin-glycoconjugates,humic acid (FA)-glycyron-glycoconjugates which are prepared through selective degradation and branching modification were illustrated with similar pharmacophore (functional group) of Terpenoids, steroids by MTT experiment and flow cytometer.

Thermodynamics of 1,4-diisocyanatobutane in the range from T → (0 to 360) K at standard pressure

The temperature dependence of heat capacity of 1,4-diisocyanatobutane in crystalline and liquid states was determined by precision adiabatic vacuum calorimetry in the temperature range (8 to 360) K at standard pressure mainly with an uncertainty of ±0.2%. Thermodynamic characteristics of fusion, the first and the second cryoscopic constants, the isochoric heat capacity C v and its lattice C v,lat, and atomic at C v,at components were estimated. The data were used to calculate the standard thermodynamic functions C p , m ∘ / R , Δ ∘ T H m ∘ / R , Δ ∘ T S m ∘ / R and Φ m ∘ / R = Δ ∘ T S m ∘ / R - Δ ∘ T H m ∘ / TR (where R is the universal gas constant) over the range T → (0 to 360) K. The energy of combustion was measured at T = 298.15 K by the bomb calorimetry. The standard thermodynamic characteristics of formation, namely, the enthalpy Δ f H m ∘ , the entropy Δ f S m ∘ , the Gibbs function Δ f G m ∘ and ln K f ∘ of 1,4-diisocyanatobutane were evaluated at T = 298.15 K.

Thermodynamics of dimethylene urethane and poly(dimethylene urethane) in the range from T → 0 to 490 K at standard pressure

By high-precision dynamic calorimetry the temperature dependences of heat capacity of dimethylene urethane (DMU) between 320 and 370 K and partially crystalline poly(dimethylene urethane) (PDMU) in the range 326–490 K at standard pressure have been determined within ±1.5%. The thermodynamic characteristics of fusion of the substances, namely the temperature interval of melting, temperature, enthalpy and entropy of fusion, as well as the characteristics of devitrification and glassy state for poly(dimethylene urethane) have been estimated. The first and the second cryoscopic constants have been calculated for dimethylene urethane. The experimental data obtained in the present work and literature findings on the heat capacity of the substances were used to calculate their thermodynamic functions: the heat capacity C° p ( T), enthalpy H°( T)− H°(0), entropy S°( T) and Gibbs function G°( T)− H°(0) over the range from T→0 to (370–480) K. Based on the data, the thermodynamic characteristics of polymerization process with five-membered ring opening Δ pol H°, Δ pol S° and Δ pol G° of dimethylene urethane with the formation of linear partially crystalline poly(dimethylene urethane) have been evaluated.

Thermodynamics of hexachlorocyclotriphosphazene and octachlorocyclotetraphosphazene fromT → 0 toT = 450 K

In adiabatic vacuum and dynamic calorimeters, the temperature dependence of the standard molar heat capacity Cp , moof hexachlorocyclotriphospazene and octachlorocyclotetraphosphazene has been determined at temperatures in the range T= 5 K to T= 450 K: from T= 5 K to T= 340 K with an accuracy of about 0.2 per cent, and with an accuracy of 0.5 to 1.5 per cent between T= 340 K and T= 450 K. The temperatures, enthalpies, and entropies of melting of the above compounds have been determined. The experimental data were used to calculate the thermodynamic functions Cp , mo/R , Δ0THmo(R·K), Δ0TSmo/R , and Φmo=ΔT 0 Smo−ΔT 0 Hmo/T( where R is the universal gas constant) in the range T→ 0 to T= 450 K, and the standard thermochemical parameters of formation ΔfSmo, ΔfGmo, and lg Kfof the cyclophosphazenes from the elements at T= 298.15 K. The isochoric heat capacities CV , mof both chlorocyclophosphazenes have been estimated over the range T→ 0 to Tfus. The first and the second cryoscopic constants have been determined. The difference in the thermodynamic properties for one phosphazene group (–NPCl2–) has been explained in terms of the different compositions and structure of the rings.

Thermodynamic properties of 1-trimethylsilyl-1-propyne fromT=8 K toT=330 K

In an adiabatic vacuum calorimeter the temperature dependence of the standard molar heat capacityCp,m° of 1-trimethylsilyl-1-propyne (total mole fraction of impuritiesx=0.0315) has been studied at temperatures between 8 K and 330 K, to within 0.2 per cent. The temperature and enthalpy of melting of the compound have been measured. The experimental data were used to calculate the thermodynamic characteristics of melting of 1-trimethylsilyl-1-propyne of 100 per cent purity:Tfus°=204.42 K, ΔfusHm°/R=1318±6, ΔfusSm°/R=6.45±0.03 (whereRis the universal gas constant) and the thermodynamic functions in the range 0 K to 330 K, forT=298.15 K andp=101.325 kPa,Cp,m°/R=26.76, Δ0THm°/R·K=6023, Δ0TSm°/R=37.04, and Φm°/R=16.84. The isochoric heat capacityCV,mand its components, latticeCV,lat,mand atomicCV,at,m, have been estimated in the rangeT→0 toTfus°. The first (A) and the second (B) cryoscopic constants have been determined.

Cryoscopic behavior in the binary mixtures of acetamide-sodium acetate and acetamide-sodium acetate trihydrate

The melting point depression of acetamide on addition of anhydrous sodium acetate and sodium acetate trihydrate was followed by DSC. Two sets of measurements were made for two crystalline forms in which the melts crystallized. From cryoscopic data, activity coefficients of acetamide were calculated in the concentration range 0 to 0.390 mole fraction of sodium acetate and 0 to 0.376 mole fraction of sodium acetate trihydrate. Activities of the salt components were calculated from the activities of the solvent using a simple analytical method. From melting point depression data and the known molar cryoscopic constant of acetamide, the Van't Hoff dissociation factor was calculated for both anhydrous and hydrated sodium acetate in the concentration ranges studied.

The molecular weight of liquid paraffin by cryoscopy

The number-average molecular weight for spectroscopy-grade liquid paraffin was determined by cryoscopy in benzene to be 348. Attention is drawn to the importance of empirically obtaining the cryoscopic apparatus constant, minimising the error in temperature measurement by ensuring the constancy of ambient conditions and keeping the total freezing-point depression within 0.5 °C.

ChemInform Abstract: PHASE DIAGRAM OF THE SODIUM CHLORIDE‐ALUMINUM CHLORIDE SYSTEM NEAR EQUIMOLAR COMPOSITION, WITH DETERMINATION OF THE CRYOSCOPIC CONSTANT, THE ENTHALPY OF MELTING, AND OXIDE CONTAMINATIONS

Chemischer InformationsdienstVolume 15, Issue 22 Physical Inorganic Chemistry ChemInform Abstract: PHASE DIAGRAM OF THE SODIUM CHLORIDE-ALUMINUM CHLORIDE SYSTEM NEAR EQUIMOLAR COMPOSITION, WITH DETERMINATION OF THE CRYOSCOPIC CONSTANT, THE ENTHALPY OF MELTING, AND OXIDE CONTAMINATIONS R. W. BERG, R. W. BERGSearch for more papers by this authorH. A. HJULER, H. A. HJULERSearch for more papers by this authorN. J. BJERRUM, N. J. BJERRUMSearch for more papers by this author R. W. BERG, R. W. BERGSearch for more papers by this authorH. A. HJULER, H. A. HJULERSearch for more papers by this authorN. J. BJERRUM, N. J. BJERRUMSearch for more papers by this author First published: May 29, 1984 https://doi.org/10.1002/chin.198422019AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume15, Issue22May 29, 1984 RelatedInformation

Phase diagram of the sodium chloride-aluminum chloride system near equimolar composition, with determination of the cryoscopic constant, the enthalpy of melting, and oxide contaminations

Phase diagram of the sodium chloride-aluminum chloride system near equimolar composition, with determination of the cryoscopic constant, the enthalpy of melting, and oxide contaminations

Binary mixtures: CH 3CH 2CONH 2 + (Na, K)/(CNS, ClO 4)

The enthalpy of fusion of propionamide is measured by the DSC method, and liquid—solid equilibrium temperatures are measured for the binary systems CH 3CH 2CONH 2+(Na, K)/(CNS, ClO 4). The cryoscopic thermodynamic constant is compared with the experimental value. It was found that supercooling phenomena in these systems are very limited.

Investigations of sodium acetate trihydrate for solar latent heat storage, controlling the melting point

The addition of different acetate salts and acetamide lowers the melting point of sodium acetate trihydrate. Between 0–10% of lithium acetate dihydrate a linear relationship was observed between the melting point and the modal concentration, and the cryoscopic constant of K f = −6.8° C (±10%) was evaluated. Information on dissociation or dimerization of the various additives could be deduced from the results. The positive properties of sodium acetate trihydrate were retained.

Thermodynamic study of phase transitions in 2-methylpropan-2-ol

The results of an accurate thermal analysis on highly purified samples of 2-methylpropan-2-01 supply evidence for the supposition of the existence of three Crystalline phases, which we indicate as crystal I (mp 25.62 C), crystal I1 (mp 25.00 C), and crystal I11 (mp 21.66 C). A two-slde transltlon: crystal I G I1 has been observed at 14.1 O C . Crystal 111, by cooling, undergoes a sluggish transltlon Into crystal 11 at 9 OC. Cryoscopic behavior of solutions of carbon tetrachloride, n-heptane, and sulfolane is consistent with the above results. Metastable equilibria may be detected owlng to the fact that the freezing points of the three crystalline phases fall withln a narrow temperature range. The cryoscopic constants of the three solid phases have been calculated and fusion entalpies derived. Negative conclusions are drawn concerning the use of 2-methylpropan-2-01 as a reliable solvent in cryoscopy. From thermodynamic data only crystal I1 Is suspected, possessing some globular character.

Use of differential calorimeter for establishing temperature standards

A differential calorimeter was used to set up and critically evaluate a series of organic substances as temperature standards over the range 50–330°. The conditions for acceptance of a standard substance were a sufficient degree of purity, thermal stability, absence of polymorphism, a suitable cryoscopic constant, low volatility and ready availability. Zone refining was mentioned as a method of purification to obtain the minimum degree of required purity at 99.9 mole per cent.

Solvent-solute interactions in dimethylsulfoxide

The osmotic and activity coefficients of six non-electrolytes and ten electrolytes in dimethylsulfoxide have been measured by the depression of the freezing temperature. A cryoscopic constant of (4.40 ± 0.01) K kg mol −1 has been determined for the solvent. The behavior of non-electrolytes both as to solubility and osmotic coefficients is intermediate between that in water and in ethylene carbonate. Ethylene carbonate and dimethylsulfoxide are both polar aprotic solvents but the smaller size of the latter apparently allows it to solvate both electrolytes and non-electrolytes more effectively. Solvent size is apparently more important than dielectric constant or dipole moment in determining the properties of solutions. The osmotic and activity coefficient of salts decrease in the sequence: Li + > NA + > K + > Cs + > NH + 4 > (C 2 H 5 ) 4 N + . The ammonium ion is apparently not solvated by DMSO through hydrogen bonding.