Heats of Hydrolysis and Formation of Dimethoxychloroborane

The heat of hydrolysis of dimethoxychloroborane has been measured; for the reaction, (CH3O)2BCl(liq)+3H2O(liq)=H3BO3(c)+2CH3OH(liq)+HCl(g)ΔH(25°C)=−26.6±0.8kj/mole=−6.4±0.2kcal/mole.From this, we have calculated the heat of formation of dimethoxychloroborane: for the liquid, ΔHf° (25 °C) = −782.1 ± 1.8 kj/mole (−186.9±0.4 kcal/mole), and for the gas, ΔHf° (25 °C) = −747.9 ±2.2 kj/mole (−178.8±0.5 kcal/mole).     

Heat of Formation of N-Dimethylaminodiborane

The heat of reaction of N-dimethylaminodiborane with water has been determined according to the reaction: (CH3)2NB2H5(g)+6H2O(liq)=(CH3)2NH(g)+2H3BO3(c)+5H2(g),ΔH(25°C)=−374.99±2.71kj/mole=−89.62±0.65kcal/mole.A combination of this value with the heat of vaporization, and with the heats of formation of boric acid, dimethylamine, and water gives for liquid N-dimethylaminodiborane: ΔHf°(25 °C) = ?36.22 ± 0.75 kcal/mole.     

Heat of Oxidation of Aqueous Sulfur Dioxide With Gaseous Chlorine

The heat of oxidation of aqueous sulfur dioxide with gaseous chlorine has been determined by calorimetric methods. The results correspond to the reaction: Cl2(g)+SO2⋅2500H2O+2502H2O=H2SO4⋅2500H2O+2(HCl⋅1250H2O),ΔH(25°C)=−77.28±0.14kcal/mole.The heat of formation of aqueous sulfuric acid (in 2500 moles of water) has been calculated to be −213.92 kcal/mole.     

Heat of Decomposition of Potassium Perchlorate

The heat of decomposition of potassium perchlorate into potassium chloride and oxygen has been determined in a bomb calorimeter. The process may be represented by the equation: KClO4(c)=KCl(c)+2O2(g),ΔH°(25°C)=−4.02±0.34kj/mole,=−0.96±0.08kcal/mole.Combination of this datum with the heat of formation of KCl(c) gives −103.22 ±0.15 kcal/mole for the standard heat of formation of KClO₄(c) at 25 °C.     

Heats of Hydrolysis and Formation of Potassium Borohydride

The heat of reaction of potassium borohydride with 0.060 molal HCl has been measured by solution calorimetry. The heat of solution of the hydrolysis products has also been measured and combined with certain literature values to calculate the process: KBH4(c)+HCl(g)+3H2O(liq)→KCl(c)+H3BO3(c)+4H2(g),ΔH°(25°C)=−354.06±1.84kj/mole(−84.62±0.44kcal/mole).A combination of this value with literature values for the heats of formation of HCl(g), H₂O(liq), KCl(c), and H₃BO₃(c) gives for KBH₄(c): ΔHf°(25°C) = ?228.86 ± 2.30 kj/mole(?54.70 ± 0.55 kcal/mole).Other data on the heats of formation of the alkali-metal borohydrides are discussed briefly.     

Heat of Formation of Titanium Trichloride

A calorimetric comparison of the heat of hydrolysis of TiCl₄(liq) with the heat of oxidation and hydrolysis of TiCl₃(c) has been made. The following value is reported for the combination of these data according to the process: TiCl3(c)+½I2(c)+HCl(g)→TiCl4(liq)+HI(g),ΔH°(25°C)=8.37±0.30kcal/mole.A combination of this value with −192.3 ±0.7 kcal/mole for the heat of formation of TiCl₄(liq) and with the standard heats of formation of HCl(g) and HI(g) gives for TiCl₃(c), ΔHf°(25 °C) = −172.4±0.8 kcal/mole.     

Heat of Formation of Titanium Tetraiodide

The heat of formation of titanium tetraiodide was determined relative to that of titanium tetrabromide by comparison of their heats of hydrolysis in dilute sulfuric acid. The difference in the heats of formation may be expressed by the equation: TiI4(c)+2Br2(liq)=TiBr(c)+2I2(c),ΔH(25°C)=−230.91±0.75kj/mole(−55.19±0.18kcal/mole).By taking the heat of formation of TiBr₄(c) as −616.72 ±4.60 kj/mole, the heat of formation of TiI₄(c) is calculated to be −385.81 ±4.64 kj/mole (−91.21 ±1.11 kcal/mole). The heats of hydrolysis of TiBr₄ and TiCl₄ were similarly measured; the value obtained for the difference (186.77 ±1.34 kj/mole) is in good agreement with the difference between the directly determined heats of formation (187.11 ±5.35 kj/mole).     

Precipitation and Solubility of Calcium Hydrogenurate Hexahydrate

Solid phases formed in the quaternary system: uric acid—calcium hydroxide —hydrochloric acid—water aged for 2 months at 310 K were studied to determine conditions for calcium hydrogenurate hexahydrate, Ca(C₅H₃N₄O)₂ · 6H₂O precipitation. The precipitates were identified by chemical and thermogravimetric analyses, x-ray powder diffraction, infrared spectroscopy, light microscopy, and scanning electron microscopy. In the precipitation diagram the concentration region in which calcium hydrogenurate hexahydrate precipitated as a single solid phase was established.The solubility of calcium hydrogenurate hexahydrate was investigated in the pH range from 6.2 to 10.1 at different temperatures. The total soluble and ionic concentration of calcium (atomic absorption spectroscopy and Ca-selective electrode), total urate concentration (spectrophotometry), and pH were determined in equilibrated solutions. The data are presented in the form of tables and chemical potential diagrams. By using these data the thermodynamic solubility products of calcium hydrogenurate hexahydrate, K_s = a(Ca²⁺) · a²(C₅H₃N₄O₃⁻), were determined: pKs=10.12±0.07at288K,pKs=9.81±0.09at298K,pKs=9.28±0.04at310K,andpKs=9.01±0.03at318K.The formation of calcium hydrogenurate hexahydrate crystals in urinary tract of patients with pathologically high concentrations of calcium and urates (hypercalciuria and hyperuricosiuria) is possible.     

Heat of Formation of Beryllium Chloride

The heat of formation of beryllium chloride has been determined, by the direct combination of the elements in a calorimeter, according to the process, Be(c)+Cl2(g)=BeCl2(c),ΔH°(25°C)=−493.85±2.35kj/mole,=−118.03±0.56kcal/mole.The data obtained by other investigators are discussed briefly.     

Heat of Combustion of Borazine,B3N3H6

The heat of combustion of liquid borazine has been determined according to the following equation: B3N3H6(liq)+15/4O2(g)+3/2H2O(liq)=3H3BO3(c)+3/2N2(g),ΔH°(25°C)=−2313.3±12.6kj/mole(−552.90±3.0kcal/mole).From this value the heat of formation of liquid borazine may be calculated as ΔHf°(25 °C) = −548.5 ± 13.4 kj/mole (−131.1 ± 3.2 kcal/mole), and for the gas, ΔHf°(25 °C) = −519.2 ± 13.4 kj/mole (−124.1 ± 3.2 kcal/mole).     

Heat of Formation of Decaborane

The heat of formation of crystalline decaborane has been determined by calorimetric measurement of the heat of decomposition: B10H14(c)→10B(am)+7H2(g),ΔH(25°C)=82.8±5.9kj/mole,(19.8±1.4kcal/mole).With the heat of transition of crystalline to amorphous boron taken as 0.40 kcal/mole, we obtain for the heat of formation of decaborane: ΔHf298.15°=−66.1kj/mole,(−15.8kcal/mole).     

Vapor Pressures of Platinum,Iridium, and Rhodium

The vapor pressures of platinum, iridium, and rhodium have been measured using a microbalance technique based on the Langmuir method. Heats of sublimation at 298 °K were calculated with the aid of free energy functions. The least square lines for the vapor pressure data, the heats of sublimation, and the normal boiling points obtained were as follows:

1. Platinum: LogPatm=6.761−27,575T(1,916to2,042°K)ΔHs°(298)=134.9±1.0kcal/molebp=4,100±100°K
2. Iridium: LogPatm=7.139−33,337T(1,986to2,260°K)ΔHs°(298)=159.9±2.0kcal/molebp=4,800±100°K
3. Rhodium: LogPatm=6.894−27,276T(1,709to2,075°K)ΔHs°(298)=132.5±2.0kcal/molebp=4,000±100°K.

The indicated uncertainties are estimates of the overall limits of error. The value of the gas constant R used in the calculation of ΔHs° is 1.98726 cal/degree mole.     

Heats of Formation of Lithium Perchlorate,Ammonium Perchlorate,and Sodium Perchlorate

Calorimetric measurements of the heats of solution of LiClO₄(c), NH₄ClO₄(e), and NaClO₄(c) have been made. The results have been combined with the heats of formation of KClO₄(c), KCl(c), LiCl(c), NH₄Cl(c), and NaCl(c), to obtain the following heats of formation: LiClO4(c),ΔHf°(25°C)=−380.27±1.21kj/mole=−90.89±0.29kcal/mole,NH4ClO4(c),=−295.98±1.35kj/mole=−70.74±0.32kcal/mole,NaClO4(c),=−382.75±0.93kj/mole=−91.48±0.22kcal/mole.A brief summary of other recent data has been included.     

Vapor Pressures of Ruthenium and Osmium

The vapor pressures and heats of sublimation of ruthenium and osmium have been measured using a microbalance technique based on the Langmuir method. Heats of sublimation at 298 °K were calculated with the aid of free energy functions. Least squares lines for the vapor pressure data, heats of sublimation, and normal boiling points were obtained as follows :

1. Ruthenium: LogPatm=7.500−32,769T(1940−2377°K) ΔHs°(298)=156.1±1.5kcal/molebp=4150±100°K
2. Osmium: LogPatm=7.484−39,880T(2157−2592°K) ΔHs°(298)=189.0±1.4kcal/molebp=5300±100°K

The indicated uncertainties are estimates of the overall limits of error.     

Heat of Formation of Calcium Aluminate Monosulfate at 25 °C

The heat of formation of calcium aluminate monosulfate, 3CaO·Al₂O₃·CaSO₄·12H₂O, at 25 °C, and of less completely hydrated samples of the same compound, was determined by the heat-of-solution method, with 2N HCl as the solvent, and 3CaO·Al₂O₃·6H₂O(c) and CaSO₄·2H₂O(c), as the reactants. The results were as follows:

Electron-Impact Total Ionization Cross Sections of Hydrocarbon Ions

The Binary-Encounter-Bethe (BEB) model for electron-impact total ionization cross sections has been applied to CH2+, CH3+, CH4+, C2H2+, C2H4+, C2H6+ and H₃O⁺. The cross sections for the hydrocarbon ions are needed for modeling cool plasmas in fusion devices. No experimental data are available for direct comparison. Molecular constants to generate total ionization cross sections at arbitrary incident electron energies using the BEB formula are presented. A recent experimental result on the ionization of H₃O⁺ is found to be almost 1/20 of the present theory at the cross section peak.     

Dissociation Constant of 4-Aminopyridinium Ion in Water From 0 to 50 °C and Related Thermodynamic Quantities

The dissociation constant of 4-aminopyridinium ion in water at 11 temperatures from 0° to 50° C has been determined from electromotive force measurements of 19 approximately equimolal aqueous buffer solutions of 4-aminopyridine and 4-aminopyridinium chloride. Cells without liquid junction were used; the cell is represented as follows: Pt; H₂(g), H₂NC₅H₄N ? HCl(m₁), H₂NC₅H₄N(m₂), AgCl; Agwhere m is molality.Between 0° and 50° C, the dissociation constant (K_bh) is given as a function of temperature (T) in degrees Kelvin by −logKbh=2575.8T+0.08277+0.0013093TThe changes of Gibbs free energy (ΔG°), of enthalpy (ΔH°), of entropy (ΔS°), and of heat capacity (ΔC_p°) for the dissociation process in the standard state were calculated from the constants of this equation. At 25° C the following values were found: −logKbh=9.114,ΔG°=52,013jmole−1,ΔH°=47,090jmole−1,ΔS°=−16.5jdeg−1mole−1,ΔCp°=−15jdeg−1mole−1.Thermodynamic constants for the basic dissociation of 4-aminopyridine at 25° C were also computed.     

Melting and Vaporization of the 1223 Phase in the System (Tl-Pb-Ba-Sr-Ca-Cu-O)

The melting and vaporization of the 1223 [(Tl,Pb):(Ba,Sr):Ca:Cu] oxide phase in the system (Tl-Pb-Ba-Sr-Ca-Cu-O) have been investigated using a combination of dynamic methods (differential thermal analysis, thermogravimetry, effusion) and post-quenching characterization techniques (powder x-ray diffraction, scanning electron microscopy, energy dispersive x-ray spectrometry). Vaporization rates, thermal events, and melt compositions were followed as a function of thallia loss from a 1223 stoichiometry. Melting and vaporization equilibria of the 1223 phase are complex, with as many as seven phases participating simultaneously. At a total pressure of 0.1 MPa the 1223 phase was found to melt completely at (980 ± 5) °C in oxygen, at a thallia partial pressure (p_Tl2O) of (4.6 ± 0.5) kPa, where the quoted uncertainties are standard uncertainties, i.e., 1 estimated standard deviation. The melting reaction involves five other solids and a liquid, nominally as follows: 1223→1212+(Ca,Sr)2CuO3+(Sr,Ca)CuO2+BaPbO3+(Ca,Sr)O+LiquidStoichiometries of the participating phases have been determined from microchemical analysis, and substantial elemental substitution on the 1212 and 1223 crystallographic sites is indicated. The 1223 phase occurs in equilibrium with liquids from its melting point down to at least 935 °C. The composition of the lowest melting liquid detected for the bulk compositions of this study has been measured using microchemical analysis. Applications to the processing of superconducting wires and tapes are discussed.     

Franck-Condon Factors to High Vibrational Quantum Numbers I: N2 and [... formula ...]

Franck-Condon factor arrays have been computed numerically to high vibrational quantum numbers for the band systems N2:C3II−B3II(Second Positive)N2:B3II−A3∑(First Positive)N2:A3∑−X1∑(Vegard Kaplan)N2:a1II−X1∑(Lyman-Birge-Hopfield)N2+;A2II−X2∑(Meinel)N2+:B2∑−X2∑(First Negative)and for the following ionization transitions N2X1∑→N2+X2∑N2X1∑→N2+A2IIN2X1∑→N2+B2∑