The reactivity of pyridine towards sulphuric acid at elevated temperatures

2010 ◽  
Vol 77 (10) ◽  
pp. 963-971 ◽  
Author(s):  
H. J. Den Hertog ◽  
H. C. van der Plas ◽  
D. J. Buurman
Keyword(s):  
Sulphuric Acid ◽  
Elevated Temperatures

scholarly journals An Electrochemical Study of Hydrothermal Reactions at Elevated Temperatures

2021 ◽  
Author(s):  
◽  
Edward Kazimierz Mroczek
Keyword(s):  
Dissociation Constant ◽  
Sulphuric Acid ◽  
Elevated Temperatures ◽  
Equilibrium Constants ◽  
Sodium Tetraborate ◽  
Liquid Junction ◽  
Solution Ph ◽  
Hydrogen Electrode ◽  
Cell Compartments ◽  
Temperature Variable

<p>A high temperature hydrogen electrode concentration cell based on a design published by Macdonald, Butler and Owen1, was constructed and used to study the following protolytic equilibria. Thermodynamic equilibrium constants were derived by the usual method of extrapolation to zero ionic strength. 1. The ionization of water at temperatures from 75 to 225 degrees C in 0.1, 0.3, 0.5 and 1.0 mol kg-1 KCl solution. pK degrees w = 7229.701 /T + 30.285logT - 85.007 2. The pH calibration of 0.01 and 0.05 mol kg-1 sodium tetraborate at temperatures from 75 to 250 degrees C in O.1, 0.3 and 0.5 mol kg-1 NaCl solution. 0.0l mol kg-1 Sodium Tetraborate Solution pH = -0.4830t1 + 5.5692t2 + 7.7167t3 + 8.6983 0.05 mol kg-1 Sodium Tetraborate Solution pH = -0.0455tl + 8.3987t2 + O.2123t3 8.8156 3. The second dissociation of sulphuric acid at temperatures from 75 to 225 degree C in 0.1, 0.3 and 0.5 mol kg-l KCl solution. pK degrees 2 = 5.3353t1 - 15.9518t2 - 111.4929t3 + 3.8458 pK degrees 2 = 6.1815t*1 + 12.7301t*2. + 3.0660 (up to 150 degrees C) Where the t1 to t3= and t*1 and t*2 are the Clark-Glew temperature variable terms at reference temperatures of 423.15 and 373.15 K respectively2. 4. The acid hydrolysis of K-feldspar to K-mica and quartz at a temperature of 225 degrees C. The determination of the hydrolysis equilibrium constant was limited to one temperature because of the very slow reaction rate at temperatures less than 300 degrees C. log(mK+/mH+) = 4.2 (at 225 degrees C) Where a comparison could be made, the results of this study agreed well with previously published work, with the exception of the second dissociation constant of sulphuric acid at temperatures above 150 degrees C. Accurate values for the molal dissociation constant of the KSO-4 ion pair are required at elevated temperatures before the pK degrees 2 results can be fully evaluated. This research was severely restricted by the unpredictable loss of electrical continuity between the two cell compartments at temperatures above 150 degrees C. The problem appeared to be associated with the non-wettability of the porous Teflon plug which formed the liquid junction.</p>

scholarly journals An Electrochemical Study of Hydrothermal Reactions at Elevated Temperatures

2021 ◽  
Author(s):  
◽  
Edward Kazimierz Mroczek
Keyword(s):  
Dissociation Constant ◽  
Sulphuric Acid ◽  
Elevated Temperatures ◽  
Equilibrium Constants ◽  
Sodium Tetraborate ◽  
Liquid Junction ◽  
Solution Ph ◽  
Hydrogen Electrode ◽  
Cell Compartments ◽  
Temperature Variable

<p>A high temperature hydrogen electrode concentration cell based on a design published by Macdonald, Butler and Owen1, was constructed and used to study the following protolytic equilibria. Thermodynamic equilibrium constants were derived by the usual method of extrapolation to zero ionic strength. 1. The ionization of water at temperatures from 75 to 225 degrees C in 0.1, 0.3, 0.5 and 1.0 mol kg-1 KCl solution. pK degrees w = 7229.701 /T + 30.285logT - 85.007 2. The pH calibration of 0.01 and 0.05 mol kg-1 sodium tetraborate at temperatures from 75 to 250 degrees C in O.1, 0.3 and 0.5 mol kg-1 NaCl solution. 0.0l mol kg-1 Sodium Tetraborate Solution pH = -0.4830t1 + 5.5692t2 + 7.7167t3 + 8.6983 0.05 mol kg-1 Sodium Tetraborate Solution pH = -0.0455tl + 8.3987t2 + O.2123t3 8.8156 3. The second dissociation of sulphuric acid at temperatures from 75 to 225 degree C in 0.1, 0.3 and 0.5 mol kg-l KCl solution. pK degrees 2 = 5.3353t1 - 15.9518t2 - 111.4929t3 + 3.8458 pK degrees 2 = 6.1815t*1 + 12.7301t*2. + 3.0660 (up to 150 degrees C) Where the t1 to t3= and t*1 and t*2 are the Clark-Glew temperature variable terms at reference temperatures of 423.15 and 373.15 K respectively2. 4. The acid hydrolysis of K-feldspar to K-mica and quartz at a temperature of 225 degrees C. The determination of the hydrolysis equilibrium constant was limited to one temperature because of the very slow reaction rate at temperatures less than 300 degrees C. log(mK+/mH+) = 4.2 (at 225 degrees C) Where a comparison could be made, the results of this study agreed well with previously published work, with the exception of the second dissociation constant of sulphuric acid at temperatures above 150 degrees C. Accurate values for the molal dissociation constant of the KSO-4 ion pair are required at elevated temperatures before the pK degrees 2 results can be fully evaluated. This research was severely restricted by the unpredictable loss of electrical continuity between the two cell compartments at temperatures above 150 degrees C. The problem appeared to be associated with the non-wettability of the porous Teflon plug which formed the liquid junction.</p>

Characterization of Rare-Earth Fluoride Anti-Stokes Phosphors by Scanning arid Transmission Electron Microscopy

1971 ◽  
Vol 29 ◽  
pp. 142-143
Author(s):  
N. M. P. Low ◽  
L. E. Brosselard
Keyword(s):  
Electron Microscopy ◽  
Rare Earth ◽  
Elevated Temperatures ◽  
Stoichiometric Composition ◽  
Rare Earth Ions ◽  
Crystalline Solid ◽  
Precipitation Process ◽  
Rare Earth Fluoride ◽  
Earth Fluoride ◽  
Rare Earth Fluorides

There has been considerable interest over the past several years in materials capable of converting infrared radiation to visible light by means of sequential excitation in two or more steps. Several rare-earth trifluorides (LaF3, YF3, GdF3, and LuF3) containing a small amount of other trivalent rare-earth ions (Yb3+ and Er3+, or Ho3+, or Tm3+) have been found to exhibit such phenomenon. The methods of preparation of these rare-earth fluorides in the crystalline solid form generally involve a co-precipitation process and a subsequent solid state reaction at elevated temperatures. This investigation was undertaken to examine the morphological features of both the precipitated and the thermally treated fluoride powders by both transmission and scanning electron microscopy.Rare-earth oxides of stoichiometric composition were dissolved in nitric acid and the mixed rare-earth fluoride was then coprecipitated out as fine granules by the addition of excess hydrofluoric acid. The precipitated rare-earth fluorides were washed with water, separated from the aqueous solution, and oven-dried.

Observations oh Nucleation and Growth of Voids in Nickel

1970 ◽  
Vol 28 ◽  
pp. 414-415
Author(s):  
J. L. Brimhall ◽  
H. E. Kissinger ◽  
B. Mastel
Keyword(s):  
High Purity ◽  
Growth Stage ◽  
Elevated Temperatures ◽  
Early Growth ◽  
Nucleation And Growth ◽  
Pure Nickel ◽  
Different Temperatures ◽  
Total Fluence ◽  
Neutron Exposure ◽  
Growth Of Voids

Some information on the size and density of voids that develop in several high purity metals and alloys during irradiation with neutrons at elevated temperatures has been reported as a function of irradiation parameters. An area of particular interest is the nucleation and early growth stage of voids. It is the purpose of this paper to describe the microstructure in high purity nickel after irradiation to a very low but constant neutron exposure at three different temperatures.Annealed specimens of 99-997% pure nickel in the form of foils 75μ thick were irradiated in a capsule to a total fluence of 2.2 × 1019 n/cm2 (E > 1.0 MeV). The capsule consisted of three temperature zones maintained by heaters and monitored by thermocouples at 350, 400, and 450°C, respectively. The temperature was automatically dropped to 60°C while the reactor was down.

Voids in Irradiated Tungsten and Molybdenum

1969 ◽  
Vol 27 ◽  
pp. 190-191
Author(s):  
Robert C. Rau ◽  
Robert L. Ladd
Keyword(s):  
Melting Point ◽  
Fast Neutron ◽  
Neutron Irradiation ◽  
Elevated Temperatures ◽  
Irradiation Temperature ◽  
The Body ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Metals ◽  
Face Centered

Recent studies have shown the presence of voids in several face-centered cubic metals after neutron irradiation at elevated temperatures. These voids were found when the irradiation temperature was above 0.3 Tm where Tm is the absolute melting point, and were ascribed to the agglomeration of lattice vacancies resulting from fast neutron generated displacement cascades. The present paper reports the existence of similar voids in the body-centered cubic metals tungsten and molybdenum.

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