Acid Dissociation Constant and Related Thermodynamic Quantities for Triethanolammonium Ion in Water From 0 to 50°C

Earlier studies of the dissociation constants of monoethanolammonium and diethanolammonium ions and the thermodynamic constants for the dissociation processes have been supplemented by a similar study of triethanolammonium ion from 0° to 50° C. The dissociation constant (K_bh) is given by the formula ?log K_bh = 1341.16/T + 4.6252 ? 0.0045666Twhere T is in degrees Kelvin. The order of acidic strengths of the ions is as follows: Triethanolammonium >diethanolammonium>monethanolammonium. Conversely, monoethanolamine is the strongest of the three bases. The thermodynamic constants for the dissociation of one mole of triethanolammonium ion in the standard state at 25° C are as follows: Heat content change (ΔH°) 33.450 joule mole⁻¹; entropy change (ΔS°), −36.4 joule deg⁻¹ mole⁻¹; heat-capacity change (ΔCp°), 52 joule deg⁻¹ mole⁻¹.     

Water availability in +2°C and +4°C worlds

While the parties to the UNFCCC agreed in the December 2009 Copenhagen Accord that a 2°C global warming over pre-industrial levels should be avoided, current commitments on greenhouse gas emissions reductions from these same parties will lead to a 50?:?50 chance of warming greater than 3.5°C. Here, we evaluate the differences in impacts and adaptation issues for water resources in worlds corresponding to the policy objective (+2°C) and possible reality (+4°C). We simulate the differences in impacts on surface run-off and water resource availability using a global hydrological model driven by ensembles of climate models with global temperature increases of 2°C and 4°C. We combine these with UN-based population growth scenarios to explore the relative importance of population change and climate change for water availability. We find that the projected changes in global surface run-off from the ensemble show an increase in spatial coherence and magnitude for a +4°C world compared with a +2°C one. In a +2°C world, population growth in most large river basins tends to override climate change as a driver of water stress, while in a +4°C world, climate change becomes more dominant, even compensating for population effects where climate change increases run-off. However, in some basins where climate change has positive effects, the seasonality of surface run-off becomes increasingly amplified in a +4°C climate.     

Spectrophotometric Determination of the Ionization Constant of 2,4,6-Trinitro-m-cresol in Water at 25 °C

The ionization constant of 2,4,6-trinitro-m-cresol in water at 25 °C was determined by a spectrophotometric procedure. The pK value 0.81 (K ≈ 0.16) was obtained.     

Spectrophotometric Determination of the Thermodynamic pK Value of Picric Acid in Water at 25 °C

The thermodynamic pK value of picric acid was determined spectrophotometrically in water containing hydrochloric acid to repress the ionization. The pK value 0.33 (K ≈ 0.46) was obtained from data at 450 mμ. Attempts to determine the pK value by potentiometric titrations of picric acid and by spectrophotometric measurements of picric acid solutions in the near-saturation range did not yield satisfactory results. The new pK value is compared with previously published values.     

Spectrophotometric Determination of the Ionization Constant of Dimethylpicric Acid (2,4,6-Trinitro-3,5-xylenol) in Water at 25 °C

The ionization constant of dimethylpicric acid (2,4,6-trinitro-3,5-xylenol) in water at 25 °C has been determined by a spectrophotometric method. The pK value 1.38 (K ≈0.042) was obtained. Potentiometric titrations, although less precise, yielded a pK value of the same magnitude.     

Treasure of the Past VI: Standard Potential of the Silver-Silver-Chloride Electrode from 0° to 95° C and the Thermodynamic Properties of Dilute Hydrochloric Acid Solutions

From electromotive-force measurements of the cell without liquid junction: Pt;  H₂,  HCl (m),  AgCl;  Agthrough the range 0° to 95° C, calculations have been made of (1) the standard potential of the silver–silver-chloride electrode, (2) the activity coefficient of hydrochloric acid in aqueous solutions from m (molality) =0 to m=0.1 and from 0° to 90° C, (3) the relative partial molal heat content of hydrochloric acid, and (4) the relative partial molal heat capacity of hydrochloric acid.The extrapolations were made by the method of least squares with the aid of punch-card techniques. Data from at least 24 cells were analyzed at each temperature, and 81 cells were studied at 25° C. The value of the standard potential was found to be 0.22234 absolute volt at 25° C, and the standard deviation was 0.02 millivolt at 0° C, 0.01 millivolt at 25° C, and 0.09 millivolt at 95° C. The results from 0° to 60° C are compared with earlier determinations of the standard potential and other quantities derived from the electromotive force.     

Characteristics of Oxidation and Oxygen Penetration of Alloy 690 in 600°C Aerated Supercritical Water

The oxide films formed on Alloy 690 exposed to 600°C supercritical water were characterized using mass measurement, X-ray diffraction, Raman spectroscopy, scanning electron microscopy equipped with energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. It was found that the mass gain of the alloy in supercritical water decreased with increasing exposure time. The oxide films have a double-layer structure, with an inner layer rich in Cr and outer layer rich in Ni and Fe after short time and long time exposure. The penetration of the oxide along the grain boundaries was observed, and the penetration depth increased with increasing exposure time. The grain boundaries and voids are the short-path of oxygen diffusion into the metal.     

Ionization Constants of Four Dinitrophenols in Water at 25 °C

Thermodynamic ionization constants of 2,3-, 2,5-, 3,4-, and 3,5-dinitrophenols in aqueous solution at 25° C have been determined by a spectrophotometric method. The respective values found, expressed as pK, are 4.95₉, 5.21₀, 5.42₂, and 6.69₂. pK has also been determined potentiometrically for 2,3- and 3,5-dinitrophenols; the respective values obtained are 4.98 and 6.66. The experimental pK values for all six dinitrophenols are lower than the calculated values based on pK data for phenol and the mononitrophenols.Spectral absorption curves are presented for the ionized and unionized forms of the four dinitrophenols.     

Thermodynamic Properties of Magnesium Oxide and Beryllium Oxide from 298 to 1,200 °K

As a step in developing new standards of high-temperature heat capacity and in determining accurate thermodynamic data for simple substances, the enthalpy (heat content) relative to 273 °K, of high purity fused magnesium oxide, MgO, and of sintered beryllium oxide, BeO, was measured up to 1,173 °K. A Bunsen ice calorimeter and the drop method were used. The two samples of BeO measured had surface-to-volume ratios differing by a factor of 15 or 20, yet agreed with each other closely enough to preclude appreciable error attributable to the considerable surface area. The enthalpies found for MgO are several percent higher than most previously reported values. The values are represented within their uncertainty (estimated to average ± 0.25%) by the following empirical equations³ (cal mole⁻¹ at T °K) MgO:HT°−H273.15°=10.7409T+1.2177(10−3)T2−2.3183(10−7)T3+2.26151(105)T−1−3847.94.BeO:HT°−H273.15°=11.1084T+7.1245(10−4)T2+8.40705(105)T−1−5.31245(107)T−2−5453.21.Values of enthalpy, heat capacity, entropy, and Gibbs free-energy function are tabulated from 298.15 to 1,200 °K.     

Multizone Furnace for Analysis of Fixed-Point Realizations in the Range from 1,000°C to 1,700°C

In this article, the development of a laboratory furnace specially designed for analysis of fixed-point plateau realizations in the range from 1,000 °C to 1,700 °C that enables control of various temperature distribution settings along the heating zone length is presented. A total of 13 thermocouples are built into the furnace tube wall to control the temperature as well as to measure the temperature distribution. The furnace is divided into seven independently controlled heating zones. Each heating zone comprises a MoSi₂ heating element and its dedicated DC power supply module. The furnace temperature is controlled by manipulating the output voltage of each power supply to control the temperature of each heating element, as estimated from its electrical resistance. The heating power and temperature measurement are fully controlled by a computer using an application written in Lab VIEW, allowing very flexible furnace control. The furnace can be used in air as well as in an inert atmosphere. Measurements of the temperature distribution of the furnace during a melting-point realization are presented.     

Transformation of tridymite to cristobalite below 1470° C in silica refractories

Because silica refractory has good volume stability and creep properties at high temperature, it has been used in several furnaces. However, silica has three polymorphs (quartz, tridymite and cristobalite) and each polymorph has an- type transformation. It is known that cristobalite is the stable phase of silica between 1470° C and the melting point of silica refractories. However, sometimes cristobalite was found in silica refractories used in the stable temperature region of tridymite. Therefore, the cause and mechanism of this tridymite-to-cristobalite transformation below 1470° C was studied. Although the transformation temperature of tridymite to cristobalite was also 1470° C in the sample used in this research, it decreased on addition of Al₂O₃. The apparent activation energy of the tridymite-to-cristobalite transformation was found to be 787 kJ mol^–1 above 1470° C and 176 kJ mol^–1 below 1470° C with Al₂O₃ by measuring the transformation rate. It was also observed using EPIVIA that the tridymite included CaO; however, CaO and Al₂O₃ were located on the outside of the cristobalite which was produced below 1470°C. Therefore, it is supposed that the liquid phase was produced by the penetration of Al₂O₃, and impurities in the tridymite crystal diffused outside and then silica was precipitated as cristobalite.     

Agriculture and food systems in sub-Saharan Africa in a 4°C+ world

Agricultural development in sub-Saharan Africa faces daunting challenges, which climate change and increasing climate variability will compound in vulnerable areas. The impacts of a changing climate on agricultural production in a world that warms by 4°C or more are likely to be severe in places. The livelihoods of many croppers and livestock keepers in Africa are associated with diversity of options. The changes in crop and livestock production that are likely to result in a 4°C+ world will diminish the options available to most smallholders. In such a world, current crop and livestock varieties and agricultural practices will often be inadequate, and food security will be more difficult to achieve because of commodity price increases and local production shortfalls. While adaptation strategies exist, considerable institutional and policy support will be needed to implement them successfully on the scale required. Even in the 2°C+ world that appears inevitable, planning for and implementing successful adaptation strategies are critical if agricultural growth in the region is to occur, food security be achieved and household livelihoods be enhanced. As part of this effort, better understanding of the critical thresholds in global and African food systems requires urgent research.     

Spectral and Thermodynamic Analysis of Wear Products in a B4C–ShKh15-Steel Friction Couple

We investigate the phase composition of wear products on the sliding surface of boron carbide over steel by means of thermodynamic calculations as well as scanning electron microscopy and Auger electron spectroscopy. We show that graphitization on the friction surface is attributable to the decomposition of carbon monoxide.     

Get 86–2017: State Primary Standard of Units of Radiometric Quantities and Units of Spectroradiometric Quantities in the Range of Wavelengths from 0.2 to 25.0 μm

Measurement Techniques - The composition and metrological characteristics of GET 86–2017, the State Primary Standard of the units of radiometric quantities and units of spectroradiometric...     

Mechanical and structural characterisation of Nicalon SiC fibres up to 1300°C

The resurgence of interest in metal matrix composites has been fuelled by the development of new fibres with high temperature characteristics. The new family of continuous fine ceramic fibres based on SiC or Al₂O₃ offers the possibility of producing high temperature composites with metal or ceramic matrices. The toughening of ceramics by these fibres is a particularly interesting prospect.Two types of continuous silicon carbide Nicalon monofilaments (NLP 101 and NLM 102) have been tested in air and argon up to 1300°C. Tensile and creep tests have shown that the tensile strength falls and the fibres creep above 1000°C. Different behaviour was found for the two types of fibres. The NLM 102 fibre was stronger and crept less at high temperature under small strains. However its creep lifetime was less than that of the NLP 101 fibres.These differences have been interpreted with the aid of a microstructural study. The fibres were found to contain silicon, carbon and oxygen (electron microphobe and Auger spectrometer) and SiC was also detected (X-ray diffraction and transmission electron microscopy). The modification of the amorphous and microcrystalline structures during creep have been investigated. A fine segregation of free carbon particles was detected (X-ray diffraction and ESR) and was seen to disappear during heat treatment in both types of environment studied.