Hydrolysis of Co(II) at elevated temperatures

1978 ◽  
Vol 56 (4) ◽  
pp. 435-440 ◽  
Author(s):  
Gaétan Giasson ◽  
Param H. Tewari
Keyword(s):  
Elevated Temperatures ◽  
Initial Solution ◽  
Cobalt Concentration ◽  
Liquid Junction ◽  
Solution Ph ◽  
Concentration Cell ◽  
Hydrolysis Of

Hydrolysis of Co(II) has been studied up to 200 °C using a concentration cell with liquid junction of the type Pt(H2)|H+(a1)||H+(a2)|(H2)Pt. The effect of varying the initial solution pH and cobalt concentration has been studied at different ionic strengths. The hydrothermal hydrolysis for cobalt solutions between pH 3.9 and 9.6 is consistent with the equilibrium Co2+ + H2O → CoOH+ + H+. Higher hydrolytic species are not important. Hydrolysis increases with temperature and produces a buffering action at 200 °C. Thermodynamic quantifies for the hydrolysed species are reported.

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>

scholarly journals The Hsp60 Protein of Helicobacter Pylori Exhibits Chaperone and ATPase Activities at Elevated Temperatures

BioChem ◽  
2021 ◽  
Vol 1 (1) ◽  
pp. 19-25
Author(s):  
Jose A. Mendoza ◽  
Julian L. Ignacio ◽  
Christopher M. Buckley
Keyword(s):  
Helicobacter Pylori ◽  
Heat Stress ◽  
Molecular Chaperone ◽  
Elevated Temperatures ◽  
Citrate Synthase ◽  
Gastric Epithelium ◽  
Acidic Conditions ◽  
H Pylori ◽  
Induced Aggregation ◽  
Hydrolysis Of

The heat-shock protein, Hsp60, is one of the most abundant proteins in Helicobacter pylori. Given its sequence homology to the Escherichia coli Hsp60 or GroEL, Hsp60 from H. pylori would be expected to function as a molecular chaperone in this organism. H. pylori is a type of bacteria that grows on the gastric epithelium, where the pH can fluctuate between neutral and 4.5, and the intracellular pH can be as low as 5.0. We previously showed that Hsp60 functions as a chaperone under acidic conditions. However, no reports have been made on the ability of Hsp60 to function as a molecular chaperone under other stressful conditions, such as heat stress or elevated temperatures. We report here that Hsp60 could suppress the heat-induced aggregation of the enzymes rhodanese, malate dehydrogenase, citrate synthase, and lactate dehydrogenase. Moreover, Hsp60 was found to have a potassium and magnesium-dependent ATPase activity that was stimulated at elevated temperatures. Although, Hsp60 was found to bind GTP, the hydrolysis of this nucleotide could not be observed. Our results show that Hsp60 from H. pylori can function as a molecular chaperone under conditions of heat stress.

scholarly journals Purification and properties of three (1→3)-β-d-glucanase isoenzymes from young leaves of barley (Hordeum vulgare)

1993 ◽  
Vol 289 (2) ◽  
pp. 453-461 ◽  
Author(s):  
M Hrmova ◽  
G B Fincher
Keyword(s):  
Hordeum Vulgare ◽  
Elevated Temperatures ◽  
Gel Filtration ◽  
Degree Of Polymerization ◽  
Exchange Chromatography ◽  
Purification And Properties ◽  
Young Leaves ◽  
Monomeric Proteins ◽  
Ph Range ◽  
Hydrolysis Of

Three (1->3)-beta-D-glucan glucanohydrolase (EC 3.2.1.39) isoenzymes GI, GII and GIII were purified from young leaves of barley (Hordeum vulgare) using (NH4)2SO4 fractional precipitation, ion-exchange chromatography, chromatofocusing and gel-filtration chromatography. The three (1->3)-beta-D-glucanases are monomeric proteins of apparent M(r)32,000 with pI values in the range 8.8-10.3. N-terminal amino-acid-sequence analyses confirmed that the three isoenzymes represent the products of separate genes. Isoenzymes GI and GII are less stable at elevated temperatures and are active over a narrower pH range than is isoenzyme GIII, which is a glycoprotein containing 20-30 mol of hexose equivalents/mol of enzyme. The preferred substrate for the enzymes is laminarin from the brown alga Laminaria digitata, an essentially linear (1->3)-beta-D-glucan with a low degree of glucosyl substitution at 0-6 and a degree of polymerization of approx. 25. The three enzymes are classified as endohydrolases, because they yield (1->3)-beta-D-oligoglucosides with degrees of polymerization of 3-8 in the initial stages of hydrolysis of laminarin. Kinetic analyses indicate apparent Km values in the range 172-208 microM, kcat. constants of 36-155 s-1 and pH optima of 4.8. Substrate specificity studies show that the three isoenzymes hydrolyse substituted (1->3)-beta-D-glucans with degrees of polymerization of 25-31 and various high-M(r), substituted and side-branched fungal (1->3;1->6)-beta-D-glucans. However, the isoenzymes differ in their rates of hydrolysis of a (1->3;1->6)-beta-D-glucan from baker's yeast and their specific activities against laminarin vary significantly. The enzymes do not hydrolyse (1->3;1->4)-beta-D-glucans, (1->6)-beta-D-glucan, CM-cellulose, insoluble (1->3)-beta-D-glucans or aryl beta-D-glycosides.

Enhanced red upconversion emission and its mechanism in Yb3+–Er3+ codoped α-NaLuF4 nanoparticles

2017 ◽  
Vol 41 (3) ◽  
pp. 1193-1201 ◽  
Author(s):  
Hao Lin ◽  
Dekang Xu ◽  
Anming Li ◽  
Zhiren Qiu ◽  
Shenghong Yang ◽  
...  
Keyword(s):  
Upconversion Luminescence ◽  
Upconversion Emission ◽  
Initial Solution ◽  
Solution Ph

Red upconversion luminescence is greatly enhanced through manipulation of the initial solution pH.

Immobilization of Chaetomium erraticum dextranase (CED) by adsorption on carboxylated multi walled carbon nanotubes (c-MWCNT)

2021 ◽  
Author(s):  
Yakup Aslan ◽  
Barzan Ismael Ghafour
Keyword(s):  
Storage Conditions ◽  
Reducing Sugar ◽  
Solution Ph ◽  
Multi Walled Carbon Nanotubes ◽  
Activity Yield ◽  
Walled Carbon Nanotubes ◽  
Hydrolysis Of ◽  
Dextran Solution ◽  
Burk Plot

Abstract In this study, CED was immobilized onto c-MWCNT by adsorption. Optimization of immobilization conditions (immobilization buffer's pH and molarity, c-MWCNT amount, and immobilization time) was resulted in 100% immobilization yield and 114.13% activity yield. Further, characterization of FCED and ICED was also studied. After immobilization, the optimum pH shifted from 5.0 to 6.0, while the optimum temperature (55 °C) did not change. Furthermore, kinetic constants for FCED and ICED were also determined using the Lineweaver-Burk plot. The Km value for both FCED and ICED were 54.35 g / L, while Vmax values for FCED and ICED were 2.77 μmol reducing sugar / L.mg.min and 3.19 μmol reducing sugar / L.mg.min, respectively. Moreover, there was no reduction in the initial activity of ICED after 20 consecutive uses and 30 days of storage at optimal storage conditions. Finally, 17.15% and 17.53% of the dextran in 10% dextran solution (pH 6.0) were converted to reduced sugars (IMOs and Glucose) in 12 hours using FCED and ICED, respectively. Consequently, it can be concluded that ICED obtained in this study can be effectively used for industrial production of IMOs and for hydrolysis of dextran.

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