Mutual solubility of n-butanol + water under high pressures

The mutual solubilities of {xCH₃CH₂CH₂CH₂OH+(1-x)H₂O} have been determined over the temperature range 302.95 to 397.75 K at pressures up to 2450 atm. An increase in temperature and pressure results in a contraction of the immiscibility region. The results obtained for the critical solution properties are: T_o(U.C.S.T.) = 397.85 K and x_o = 0.110 at 1 atm; $\text{(}\text{dT}{}_{\mathrm{o}}\text{d}\text{p}\text{) = ?(12.0±0.5)×10}{}^{\mathrm{?3}}\text{K atm}{}^{\mathrm{?1}}$ at p < 400 atm and $\text{(}\text{dT}{}_{\mathrm{o}}\text{d}\text{p}\text{) = ?(7.0±0.7)×10}{}^{\mathrm{?3}}\text{K atm}{}^{\mathrm{?1}}$ at 800 atm < p < 2500 atm; $\text{(}\text{dx}{}_{\mathrm{o}}\text{d}\text{T}\text{) = ?(4.0±0.5)×10}{}^{\mathrm{?4}}\text{K}{}^{\mathrm{?1}}$.     

Hydrodynamic properties and statistical coil dimensions of poly(o-chlorostyrene)

The theta temperature for the system poly(o-chlorostyrene)-methyl ethyl ketone has been determined as 24·5°. The samples used in the determination were prepared by radical polymerization. The dependence of intrinsic viscosity on molecular weight has been measured in methyl ethyl ketone at 24·5° and found to be $\text{η}{}_{\mathrm{\theta }}\text{= 4·68 × 10}{}^{\mathrm{?4}}\text{M}{}_{\mathrm{<mtext>w</mtext>}}{}^{\mathrm{<mtext>M1</mtext><mtext>2</mtext>}}$. The ratio 〈s₌²〉/M was found, by light scattering, to be 5·60 × 10^?18 cm². Analysis of the solution properties indicates that the Kurata-Yamakawa theory is valid in the vicinity of the Flory temperature (UCST).     

Dilute solution properties of poly(N-vinyl-3,6-dibromo carbazole)—III. Phase equilibrium studies

The phase relationships of poly(N-vinyl-3,6-dibromo carbazole) (PVK-3, 6-Br₂) were examined for four solvents, viz, o-chlorophenol, p-chloro-m-cresol, o-dichlorobenzene and bromobenzene. Upper critical solution temperatures (UCST) have been determined for solutions of PVK-3,6-Br, fractions in o-chlorophenol and p-chloro-m-cresol over the molecular weight range $\text{M}{}_{\mathrm{<mtext>w</mtext>}}\text{× 10}{}^{\mathrm{?4}}\text{= 125.0}\text{to}\text{4.8}$. The Flory temperature, θ, obtained from UCST for the PVK-3,6-Br₂/o-chlorophenol and PVK-3,6-Br₂/p-chloro-m-cresol systems are 66.0 and 112.9°C, respectively. The θ-temperatures were checked against molecular weight and viscosity data to determine the Mark-Houwink equations for these two theta solvents, with satisfactory agreement. The relations are

$\text{[ν] = 27.5}{}_4\text{× 10}{}^{\mathrm{?10}}\text{×}\text{M}{}^{0.50}{}_{\mathrm{<mtext>w</mtext>}}\text{(o-}\text{chlorophenol}\text{, 60.0°}\text{C}$

$\text{[ν] = 30.2}{}_4\text{× 10}{}^{\mathrm{?10}}\text{×}\text{M}{}^{0.50}{}_{\mathrm{<mtext>w</mtext>}}\text{(p-}\text{chloro}\text{-m}\text{cresol}\text{, 112.9°}\text{C}$

The characteristic ratio C_∞ = 〈R²〉₀/nl² was found to be 16.6 in o-chlorophenol at 60.0°C and 17.6 in p-chloro-m-cresol at 112.9°C. The value of the characteristic ratio C_∞ of PVK-3,6-Br₂ is of the same order of that for poly(N-vinyl carbazole). This indicates that the bromine atoms at the 3 and 6 (meta) positions have only an inappreciable effect on the hindering potential for rotation about the CC bond. This agreement of C_∞ for both polymers may also be taken as indicating that the effect of interaction between polar groups at the m-position on the hindering potential for rotation is small. The phase diagrams of PVK-3,6-Br₂ obtained in o-dichlorobenzene and bromobenzene seem to be characteristic of organized phase structures such as those found in systems exhibiting thermoreversible gelation. Light scattering measurement on PVK-3,6-Br₂ dissolved in o-dichlorobenzene, a gelation promoting solvent, and tetrahydrofuran, a very good solvent, strongly indicate that the macromolecular species in o-dichlorobenzene contain some extent supermolecular structures (aggregates, association of chain segments, etc.). These characteristic structures of PVK-3,6-Br₂ in o-dichlorobenzene and bromobenzene at 25°C are also characterized by high values of the Huggins' constant k′; for tetrahydrofuran solutions, the k′ values were in the range normally found for many good solvent-polymer systems.     

Hydrodynamic and dynamo-optical properties and conformation of cyanoethyl cellulose molecules in solution

Translational diffusion, velocity sedimentation and viscosity in acetone as well as flow birefringence (FB) and viscosity in cyclohexanone have been investigated for cyanoethyl cellulose (CEC) with degree of substitution 2.6 in the range of M = (24.5?317) × 10³. The dependences of [ν], S_o and D_o on M were obtained. The value of the hydrodynamic constant is $\text{A}{}_0\text{= 3.27 × 10}{}^{\mathrm{?10}}\text{erg deg}{}^{\mathrm{?1}}\text{mol}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>3</mtext>}}$. According to hydrodynamic data, the equilibrium rigidity of CEC molecules is characterized by the length of the Kuhn segment $\text{A = 240 ? 350}\text{A}\text{?}$ and the coefficient of hindrance to intramolecular motion σ = 4.5-5.4. The hydrodynamic diameter of the chain is 8–14 Å. According to the FB data, the value of A is 260 Å. This value is in agreement with hydrodynamic data. The high value of optical anisotropy of the monomer unit, a_| - a_⊥ = 17.8 × 10^?25 cm³, is in agreement with the structure and anisotropy of the substituting groups, and the investigation of orientation angles of FB leads to the conclusion that, apart from high equilibrium rigidity, CEC in solution is characterized by considerable kinetic chain flexibility. The data for CEC are compared with the characteristics of other cellulose esters and ethers.     

Thermophysical properties of the intermetallic Mn3MN perovskites III. Heat capacity of the solid solution Mn3.2Ga0.8N

The heat capacity of the solid solution Mn_3.2Ga_0.8N was measured between 5 to 330 K by adiabatic calorimetry. A sharp anomaly with first-order character was detected at T_A = (160.5±0.5) K, corresponding to a magnetic rearrangement and a lattice expansion. No sharp anomaly was observed at T_c ≈ 260 K where the magnetic ordering takes place; instead, a smooth shoulder was detected. The thermodynamic functions at 298.15 K are $\text{C}{}_{\mathrm{<mtext>p,</mtext><mtext>m</mtext>}}\text{R}\text{= 15.16}$, $\text{S}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{R}\text{= 18.57}$, $\text{{H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(T)?H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(0)}}\text{R}\text{= 2896}\text{K}$, $\text{?{G}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(T)?H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(0)}}\text{RT}\text{= 8.85}$. At low temperatures the coefficient for the linear electronic contribution to the heat capacity was derived: γ = (0.031±0.003) J·K^?2·mol^?1. Moreover, the different contributions to the heat capacity were obtained and the electronic origin of the phase transitions was established.     

Determination of the molecular weight of polyacrylamide fractions by osmometry

The polymerization of acrylamide, initiated with permanganate/oxalic acid, has been studied at 35 ± 0.2 in an aqueous medium under nitrogen. Samples of polyacrylamide were fractionated by the triangular fractionation method using methanol as non-solvent. Molecular weights of the fractions have been determined by viscometry and osmometry. Integral and differential distribution curves were plotted using the fractionation data. The narrow molecular weight distribution for high conversion polymers has been discussed. For fractionated samples of polyacrylamide in water at 30°, the equation $\text{[η]}{}_{\mathrm{ml/g}}\text{= 6.5 × 10}{}^{\mathrm{?3}}\text{M}{}_{\mathrm{n}}{}^{0.82}$ is applicable for the molecular weight range 4 × 10⁴ to 127 × 10⁴. This equation is very similar to the equation $\text{[η]}{}_{\mathrm{ml/g}}\text{= 6.31 × 10}{}^{\mathrm{?3}}\text{M}{}_{\mathrm{/}}{}^{0.80}$ of Scholtan. Other parameters (osmotic second virial coefficient and unperturbed dimension) have also been evaluated.     

Unperturbed dimensions of polystyrene in mixed solvents at high temperature

At 371.5 K, which is the θ-temperature for polystyrene (PS) in 3-methyl cyclohexanol (MC), intrinsic viscosities [η] have been measured for PS samples of different relative molar mass M in mixtures of MC with a thermodynamically good solvent 1,2,3,4-tetrahydronaphthalene over the whole range of solvent composition. Eleven graphical procedures have been utilised and assessed in deriving the unperturbed polymer dimensions expressed as K_θ (in the relation $\text{[η] = K}{}_{\mathrm{\theta }}\text{M}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{α}{}^3$ where α is the expansion factor). For those procedures concluded to be the most reliable, there was no influence of binary solvent composition: the value of K_θ = 78 (±1) × 10^?3 dm³ kg^?1 was the same as that obtained directly under θ-conditions.     

Laser-molecular beam measurement of hyperfine structure in the I2 spectrum

Very high resolution measurements of hyperfine structure on the P(13) and R(15), 43?0, $\text{3}{}_{\mathrm{gp}}{}_0{}^{\mathrm{+}}{}_{\mathrm{u}}\text{←}{}^1\text{Σ}{}_{\mathrm{g}}{}^{\mathrm{+}}$ transitions in iodine 127 were made using laser molecular beam spectroscopy. The observed linewidth was 300 kHz (fwhm) giving a resolution of 5 × 10^?10 The observed spectrum was fitted to obtain a quadrupole coupling strength difference of ΔeQq = 1906 ± 2 MHz and a spin rotation interaction strength difference of ΔC_I = 181 ± 7 kHz between the upper and lower levels of the P(13) transition. For the R (15) transition ΔeQq = 1905 ± 2 MHz and ΔC_I = 167 ± 5 kHz.     

Dilute solution properties of polylaurolactam

For a number of fractions and unfractionated samples of polylaurolactam, molecular weights ($\text{M}{}_{\mathrm{<mtext>w</mtext>}}\text{= 1 × 10}{}^4\text{?12·5 × 10}{}^4$) were measured by the light-scattering method in a mixed solvent of m-cresol with 60 vol. % 2,2,3,3-tetrafluoropropanol; intrinsic viscosities were determined in m-cresol and 96% H₂SO₄, and the constants of the Mark-Houwink equation were calculated. The calculated values of the characteristic ratio of unperturbed dimensions (virtually identical for m-cresol and 96% H₂SO₄) were compared with the respective values for polypyrrolidone and polycaprolactam. It was found that the higher frequency of the CONH-groups reduces the rigidity of the polyamide chain.     

EPR and magnetization of GdGa2

Paramagnetic resonance and magnetic measurements were performed on powdered samples of GdGa₂. The magnetic data indicated ferrimagnetic behavior with $\text{T}{}_{\mathrm{c}}\text{? 181°}\text{K}$. Above 250° K the susceptibility obeys the Curie-Weiss law $\text{χ}{}_{\mathrm{g}}\text{=}\text{2.66}{}_2\text{× 10}{}^{\mathrm{?2}}\text{(T ? 27.6)}\text{emu/g-Oe}$ which corresponds to an effective moment of 7.95 Bohr magnetons. Over the range from 190 to 300°K the data obey a Néel type law, $\text{χ}{}_{\mathrm{g}}{}^{\mathrm{?1}}\text{= 35.95 (T ? 12.5) ?}\text{2.20 × 10}{}^4\text{(T ? 177)}$, which is indicative of ferrimagnetic order. The resonance measurements were performed at 9.013 gHz at 247, 296, and 349°K. The spectra were analyzed with a computerized curve-fitting technique that involves a linear combination of Lorentzian absorption and dispersion susceptibility components. Following demagnetization corrections, the g-factor was found to be 1.983₂ while the half-power, half-linewidth was 592.7 Oersteds.     

Tracer diffusion coefficient of oxide ions in LaCoO3 single crystal

The tracer diffusion coefficient, $\text{D1}{}_{\mathrm{<mtext>O</mtext>}}$, of oxide ions in LaCoO₃ single crystal was determined over the temperature range of 700–1000°C by a gas-solid isotopic exchange technique using ¹⁸O tracer. For the determination, two methods, the gas phase analysis and the depth profile measurement, were employed. Under an oxygen pressure of 34 Torr, the temperature dependence of $\text{D1}{}_{\mathrm{<mtext>O</mtext>}}$ in LaCoO₃ was expressed by

$\text{D1}{}_{\mathrm{<mtext>O</mtext>}}\text{(}\text{cm}{}^2\text{·}\text{sec}{}^{\mathrm{?1}}\text{) = 3.63 × 10}{}^4\text{exp}\text{?}\text{(74 ± 5)}\text{kcal}\text{·}\text{mole}{}^{\mathrm{?1}}\text{RT}$

$\text{D1}{}_{\mathrm{<mtext>O</mtext>}}$ at 950°C was found to be proportional to P^?0.35_O2. The diffusion of oxide ions occurs through a vacancy mechanism. The activation energy for the migration of oxide ion vacancies was estimated as 18 kcal · mole^?1.     

Cryogenic degradation of polystyrene in solution

An ultra-high molecular weight and narrow distribution polystyrene ($\text{M}{}_{\mathrm{<mtext>w</mtext>}}\text{= 7.3 × 10}{}^6$, M_w/M_n = 1.13) was dissolved in a wide range of solvents. Potential degradation by freezing was studied as a function of solvent type, concentration, cooling rate and number of freezing cycles. Cryogenic experiments were conducted in dioxane, tetrahydrofuran, benzene, dichloroethane, cyclohexanone, p-xylene, methyl methacrylate and styrene. The extent of degradation did not relate to a single solvent parameter, but there seemed to be a tendency towards a limited degradation in solvents with low melting points and/or solubility parameters greatly different from that of polystyrene. A low polymer concentration as well as a high cooling rate promoted chain scission, the latter parameter being the most important. In cyclohexanone and p-xylene, linear relationships were observed between the number of scission per molecule and the number of freezing cycles at high polymer concentrations and at high cooling rates. At lower concentrations and slower cooling, the relationships were non-linear suggesting a different degradation mechanism. The most extensive change in molecular weight distribution was observed on freezing in styrene. After 45 freezing cycles, an $\text{M}$_w of only 2.3 × 10⁶ was observed. The results indicate that chain scission occurred together with polymerization and combination reactions. Freezing of suitable solutions of ultra-high molecular weight polymers can thus be used as a new way of initiating polymerizations by cooling rather than heating.     

Absolute bestimmung der molekulargewichtsverteilung von anionisch und radikalisch polymerisierten polystyrolen durch lichtstreuung

The scattering function P₀ for classical elastic light scattering is specified for several molecular weight distribution functions (Schulz-, Square root-, Maxwell-, Normal-, Poisson-, Logarithmic-normal-distribution function). Precision measurements on anionic polymerized polystyrene from Pressure Chemical Co. $\text{(}\text{M}{}_{\mathrm{w}}\text{= 2 · 10}{}^6\text{and}\text{M}{}_{\mathrm{w}}\text{= 6,7 · 10}{}^6\text{)}$ and radical initiated polystyrene were performed in transdecalin with the light scattering photometer Fica 50. Comparison of experimental results with theoretical curves indicate that the anionic polystyrenes exhibit a broader distribution than given by Pressure Chemical Co. The distribution of the radical polystyrene conforms with distributions found by other methods.     

Hydrodynamic properties and equilibrium rigidity of polyamidobenzimidazole molecules in dimethylacetamide and sulphuric acid

Translational diffusion, velocity sedimentation and viscometry of polyamidobenzimidazole (PABI) solutions in the range of M = (1–61) · 10³ have been investigated in N,N-dimethylacetamide (DMA) and 98% H₂SO₄. The dependences of D₀, S₀ and [η] on M were obtained. Tsvetkov-Klenin's hydrodynamic invariant was found to be $\text{A}{}_0\text{= 3.55 · 10}{}^{\mathrm{?10}}\text{erg deg}{}^{\mathrm{?1}}\text{mol}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>3</mtext>}}$. The equilibrium rigidity of PABI molecules was characterized by the length of the Kuhn segment $\text{A = 250 ± 100}\text{A}\text{?}$. The chain diameter was $\text{7 ± 4}\text{A}\text{?}$. The values of A in 98% H₂SO₄ and in an aprotic solvent, DMA, were virtually identical, implying that the rigid-chain conformation of PABI molecules in 98% H₂SO₄ is due to their geometrical structure rather than to the protonization of amide bonds. The significance of the latter evidently increases in PABI solutions in 100% H₂SO₄ in which A is 1.5 times as high. The decrease in rigidity of PABI as compared to that of poly-p-phenylene terephthalamide ($\text{A = 400 ± 100}\text{A}\text{?}$) is in reasonable agreement with the presence of imidazole rings in PABI molecules. The presence of these rings results in kinks in the PABI chain with angles of about 30° and hence, in the depature from parallelism of rotating bonds.     

Size exclusion chromatography of cationic polyelectrolytes

Molecular weight distributions of the cationic polyelectrolyte poly(2-trimethylammonium ethyl methacrylate chloride) were determined via size exclusion chromatography (SEC) for a very broad molecular weight range ($\text{7.7 × 10}{}^3\text{?}\text{M}{}_{\mathrm{<mtext>w</mtext>}}\text{? 1.1 × 10}{}_7$). Non-size exclusion effects (ion inclusion, ion exclusion, adsorption) were controlled by special surface treatment of the stationary phase (DMAE-Fractosil^R, E. Merck) and by proper selection of the mobile phase. A non-linear effective molecular weight calibration procedure was applied to account for the high polydispersity of the polyelectrolyte standard polymers. $\text{M}{}_{\mathrm{w}}$ data from SEC experiments agree with results from light scattering, and the molecular weight distributions obtained from SEC and sedimentation velocity analysis compare well.     

Determination of the vapour pressures of o-, m-, and p-dinitrobenzene by the torsion-effusion method

The vaporization of o-, m-, and p-dinitrobenzenes was investigated by means of the torsion-effusion method and the selected equations for vapour pressure p as a function of temperature T are:

$\text{o-dinitrobenzene: log}{}_{10}\text{(}\text{p}\text{atm}\text{)=(7.03±0.34)?(4270±120)}\text{K}\text{T}\text{,m-dinitrobenzene: log}{}_{10}\text{(}\text{p}\text{atm}\text{)=(7.66±0.28)?(4400±100)}\text{K}\text{T}\text{,p-dinitrobenzene: log}{}_{10}\text{(}\text{p}\text{atm}\text{)=(8.34±0.34)?(4860±120)}\text{K}\text{T}$

The sublimation enthalpies ΔH^o(o-, 298.15 K) = (21.0 ± 0.5) kcal_th mol^?1, ΔH^o(m-, 298.15 K) = (20.8 ± 0.2) kcal_th mol^?1, and ΔH^o(p-, 298.15 K) = (23.0 ± 0.6) kcal_th mol^?1, are also derived by means of the second- and third-law treatments of the results.     

The [ν]-M relationship for linear polydimethylsiloxane (PDMS)

Weight-average molecular weights for PDMS fractions were determined by light scattering and the Archibald method in the range of 3000–300,000; the [ν]-M? relationship for toluene, 25°, was found to be

$\text{[?]=1.87 × 10}{}^{\mathrm{?2}}\text{M}{}_{\mathrm{<mtext>w</mtext>}}{}^{03658}\text{,}\text{cm3/g}$

This relationship was compared with those previously used. No upward curvature of the linear relation, log $\text{[ν] = ?(}\text{M}\text{)}$, at lower molecular weights was observed. Over the whole range of molecular weights, the [ν]-values in toluene were higher than [ν]_θ-values in bromocyclohexane at 28°.     

Standard enthalpy of solution and formation of cesium chromate. Derived thermodynamic properties of the aqueous chromate,bichromate, and dichromate ions,alkali metal and alkaline earth chromates,and lead chromate

Calorimetric measurements of the enthalpy of solution of cesium chromate gave ΔH_soln = (7622 ± 24) cal_th mol^?1 for a dilution of Cs₂CrO₄·21128H₂O. This result, along with the enthalpy of dilution gave the standard enthalpy of solution, ΔH_soln^o = (7512 ± 31) cal_th mol^?1, whence the standard enthalpy of formation, ΔH_f⁰(Cs₂CrO₄, c, 298.15 K), was calculated to be ?(341.78 ± 0.46) kcal_th mol^?1. Recomputed thermodynamic data for the formation of the other alkali metal chromates have been tabulated. From their solubilities and enthalpies of solution, the standard entropies, S⁰(298 K), of BaCrO₄ and PbCrO₄ were estimated to be (38.9 ± 0.9) and (43.7 ± 1.2) cal_th K^?1 mol^?1, respectively. There is evidence that ΔH_f⁰(SrCrO₄, c, 298.15 K) may be in error. Thermochemical, solubility, and equilibrium data, have been combined to update the thermodynamic properties of the aqueous chromate (CrO₄^2?), bichromate (HCrO₄^?), and dichromate (Cr₂O₇^2?) ions. The new values at 298.15 K are as follows:

     

19.

Persulphate initiated polymerisation of methacrylamide—I: Kinetics and molecular weight dependences     

D.R. Burfield  S.C. Ng 《European Polymer Journal》1976,12(12):873-877

A kinetic study of the aqueous persulphate initiated polymerisation of methacrylamide has shown that the rate of polymerisation is represented by the equation $\text{R}{}_{\mathrm{p}}\text{= k [}\text{M}\text{] [}\text{I}\text{]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ where the overall rate constant, $\text{k = 1.3 × 10}{}^9\text{exp}\text{(?18,400/}\text{RT}\text{) 1}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{mol}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}\text{s}{}^{\mathrm{?1}}$. Chain transfer with monomer, where C_M = 5.4 × 10^?3 at 60°, is shown to be the dominant transfer step. Comparison with kinetic studies of the analogous acrylamide polymerisation shed doubt on the ‘cage effect’ interpretation of complex orders with respect to monomer. An alternative explanation is proposed.     

20.

Heat capacity and thermodynamic functions of CsCrCl₃ and RbCrCl₃. Structural phase transitions     

Joaquín García  Juan Bartolomé  Domingo González  Rafael Navarro  Willem Jacobus Crama 《The Journal of chemical thermodynamics》1983,15(12):1109-1126

We present the heat capacities measured by adiabatic calorimetry from 6 to 350 K, and by differential scanning calorimetry from 300 to 500 K, of CsCrCl₃ and RbCrCl₃. A first-order transition at T_c = (171.1±0.1) K was detected for CsCrCl₃. The RbCrCl₃ showed at T_c = (193.3±0.1) K a transition with thermal hysteresis at temperatures just below the maximum. At T₁ = (440±10) K a continuous transition was also detected. Furthermore, at T_N ≈ 16 K, and for both compounds, a small bump due to magnetic long-range ordering was observed. The thermodynamic functions at 298.15 K are

	$\text{S}{}^0\text{/}\text{cal}{}_{\mathrm{th}}\text{K}{}^{\mathrm{?1}}\text{mol}{}^{\mathrm{?1}}$	$\text{ΔH}{}_{\mathrm{f}}{}^0\text{/kcal}{}_{\mathrm{th}}\text{mol}{}^{\mathrm{?1}}$	$\text{ΔG}{}_{\mathrm{f}}{}^0\text{/kcal}{}_{\mathrm{th}}\text{mol}{}^{\mathrm{?1}}$
CrO42?(aq)	(13.8 ± 0.5)	?(210.93 ± 0.45)	?(174.8 ± 0.5)
HCrO4?(aq)	(46.6 ± 1.8)	?(210.0 ± 0.7)	?(183.7 ± 0.5)
Cr2O72?(aq)	(67.4 ± 3.9)	?(356.5 ± 1.5)	?(312.8 ± 1.0)

     

	$\text{C}{}_{\mathrm{<mtext>p,</mtext><mtext>m</mtext>}}\text{R}$	$\text{S}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{R}$	$\text{{H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(T)?H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(0)}}\text{R}\text{K}$	$\text{?{G}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(T)?H}{}_{\mathrm{m}}{}^{\mathrm{o}}\text{(0}}\text{RT}$
CsCrCl3	15.38	26.49	3503.2	14.735
RbCrCl3	15.76	25.99	3556.8	14.384

Persulphate initiated polymerisation of methacrylamide—I: Kinetics and molecular weight dependences

A kinetic study of the aqueous persulphate initiated polymerisation of methacrylamide has shown that the rate of polymerisation is represented by the equation $\text{R}{}_{\mathrm{p}}\text{= k [}\text{M}\text{] [}\text{I}\text{]}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ where the overall rate constant, $\text{k = 1.3 × 10}{}^9\text{exp}\text{(?18,400/}\text{RT}\text{) 1}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}\text{mol}{}^{\mathrm{<mtext>?</mtext><mtext>1</mtext><mtext>2</mtext>}}\text{s}{}^{\mathrm{?1}}$. Chain transfer with monomer, where C_M = 5.4 × 10^?3 at 60°, is shown to be the dominant transfer step. Comparison with kinetic studies of the analogous acrylamide polymerisation shed doubt on the ‘cage effect’ interpretation of complex orders with respect to monomer. An alternative explanation is proposed.     

Heat capacity and thermodynamic functions of CsCrCl3 and RbCrCl3. Structural phase transitions

We present the heat capacities measured by adiabatic calorimetry from 6 to 350 K, and by differential scanning calorimetry from 300 to 500 K, of CsCrCl₃ and RbCrCl₃. A first-order transition at T_c = (171.1±0.1) K was detected for CsCrCl₃. The RbCrCl₃ showed at T_c = (193.3±0.1) K a transition with thermal hysteresis at temperatures just below the maximum. At T₁ = (440±10) K a continuous transition was also detected. Furthermore, at T_N ≈ 16 K, and for both compounds, a small bump due to magnetic long-range ordering was observed. The thermodynamic functions at 298.15 K are