Analytical applications of reaction-rate-promoting effects. Tris(1,10-phenanthroline)iron(II)-chromium(VI)indicator reaction

1974 ◽  
Vol 46 (8) ◽  
pp. 1090-1094 ◽  
Author(s):  
V. V. S. Eswara. Dutt ◽  
Horacio A. Mottola
Keyword(s):  
Reaction Rate ◽  
Indicator Reaction ◽  
Chromium Vi ◽  
Analytical Applications

Non-classical hydrogen bond triggered strand displacement for analytical applications and DNA nanostructure assembly

2018 ◽  
Vol 42 (9) ◽  
pp. 6636-6639 ◽  
Author(s):  
Manli Han ◽  
Qingsheng Fan ◽  
Yi Zhang ◽  
Lida Xu ◽  
Changyuan Yu ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Reaction Rate ◽  
Cyanuric Acid ◽  
Strand Displacement ◽  
Fast Reaction ◽  
Dna Nanostructure ◽  
Analytical Applications ◽  
Classical Hydrogen Bond ◽  
Fast Reaction Rate

A novel strand displacement triggered by the non-classical hydrogen bond between cyanuric acid and adenine exhibits a fast reaction rate.

A Kinetic Photometric Method For Benzalkonium Chloride Determination In Eye Drops

2018 ◽  
pp. 177-182
Author(s):  
Mykola Blazheyevskіy ◽  
Olena Koval’ska
Keyword(s):  
Correlation Coefficient ◽  
Linear Dependence ◽  
Peracetic Acid ◽  
Benzalkonium Chloride ◽  
Reaction Rate ◽  
Photometric Method ◽  
Eye Drops ◽  
Indicator Reaction ◽  
Chloride Determination

A novel sensitive kinetic photometric method for the Benzalkonium Chloride (BAC) determination has been developed. The method is based on the ability to inhibit the reaction of Acetylcholine hydrolysis by cholinesterase. The reaction rate is evaluated by the non-hydrolysed Acetylcholine residue, which is determined by the amount of Peracetic acid, produced during the interaction with the excess of H 2 O 2 . Indicator reaction is an interaction of p-phenetidine with Peracetic acid that leads to the formation of 4,4'-azoxyphenetole with λ max = 358 nm (lg ε = 4.2). The conditions affecting the reaction (reagents concentration, pH, order of addition of reagents, stability in time) have been optimized. The linear dependence has been obeyed in the range of (1.4-8.4)·10 -6 mol L -1 of BAC with correlation coefficient of 0.999. The assay LOQ (20 % of the inhibition degree) has been 1.9·10 -6 mol L -1 . The proposed method has been successfully applied to the analysis of the eye drops and has shown an accuracy and reliability of the results obtained.

Oxidation of DL-penicillamine by chromium(VI). Kinetics of formation of the thioester intermediate

1994 ◽  
Vol 72 (7) ◽  
pp. 1637-1644 ◽  
Author(s):  
Joaquin F. Perez-Benito ◽  
Driss Lamrhari ◽  
Conchita Arias
Keyword(s):  
Reaction Rate ◽  
Aqueous Media ◽  
Bimolecular Reaction ◽  
Spectrophotometric Detection ◽  
State Behavior ◽  
Chromium Vi ◽  
Specific Effects ◽  
Kinetics Of Formation ◽  
Kinetics Of ◽  
Catalytic Power

The kinetics of formation of the thioester involved as an intermediate in the reaction between chromium(VI) and DL-penicillamine in aqueous media (pH = 1–8) containing different buffers (acetate, citrate, and phosphate) has been studied by monitoring the disappearance of chromium(VI) at 370 nm and application of the initial-rates method. The initial rate is directly proportional to the initial concentrations of both oxidant and reductant, and the rate vs. pH plots show bell-shaped profiles. The reaction is catalyzed by the buffer present in the medium, the catalytic power of each buffer increasing in the order acetate < citrate < phosphate. This is explained in terms of a mechanism involving the formation of a complex between the acidic form of the buffer and HCrO4− previous to the formation of the thioester. Potassium chloride and sodium sulfate do not seem to have important specific effects on the reaction rate, their effect being that of an acceleration of the reaction as the ionic strength increases. On the contrary, the sulfates of magnesium, manganese(II), and zinc (the latter only in the presence of acetate buffer) have specific effects, indicating the probable formation of several complexes. The spectrophotometric detection of the thioester at 430 nm has allowed to confirm some of the conclusions extracted from the measurement of initial rates, and suggests that this intermediate might approach a steady-state behavior in the three buffers at pH > 6.25, and also that a bimolecular reaction with DL-penicillamine might be involved in its destruction.

A kinetic model that describes removal of chromium VI from rinsing waters of the metal finishing industry by electrochemical processes

2000 ◽  
Vol 42 (5-6) ◽  
pp. 55-61 ◽  
Author(s):  
S.A. Martínez ◽  
M.G. Rodríguez ◽  
C. Barrera
Keyword(s):  
Reaction Rate ◽  
Treatment Time ◽  
Electrochemical Treatment ◽  
Ferrous Ions ◽  
Chromium Vi ◽  
Electrochemical Processes ◽  
Iron Salts ◽  
Sludge Characterization ◽  
Characterization Study ◽  
Electrode Passivation

A study was made to remove Chromium VI (Cr6+), present in large quantities in the rinsing waters from the plating industry, using electrochemical treatment. Large amount of Cr6+ are found. It was found that the reaction rate followed a variable kinetic order at concentrations up to 1700 mg Cr6+/L. It was also noticed that Cr6+ reduction depended on the ferrous ions (Fe2+) released at the anode, the cathode reactions and the acidic corrosion on electrodes. Iron salts produced electrode passivation and it caused a 50% increase in treatment time and power requirements. Eliminating the salt formation at the anode could reduce this effect. Using electrochemical processes it is possible to reuse treated waters in the rising stages of the plating industry owing to the fact that final Cr6+ concentration is less than 0.5 mg/L. Finally, a sludge characterization study revealed that residue generated in the process is not considered dangerous according to Mexican environmental protection standards.

Impact of various inorganic oxyanions on the removal rates of hexavalent chromium mediated by zero-valent iron

2010 ◽  
Vol 7 (3) ◽  
pp. 250 ◽  
Author(s):  
Mario Rivero-Huguet ◽  
William D. Marshall
Keyword(s):  
Soil Solution ◽  
Active Sites ◽  
Reaction Rate ◽  
Soil Extract ◽  
Zero Valent Iron ◽  
Model Decomposition ◽  
Chromium Vi ◽  
Rate Of Reaction ◽  
Mediated Reduction ◽  
Model Reactions

Environmental context.Oxyanions in soil extract can interfere with the zero valent iron induced reduction of chromium(VI) to chromium(III). At pH 6, the reaction rate was decreased (2 to 6-fold) by an equivalent of arsenate, phosphate or silicate but was increased by sulfate and remained unchanged by borate or nitrate. At pH 2, not only was the rate of reaction dramatically increased (∼900-fold) but interferences from the major components of soil solution (nitrate, silicate and sulfate) were minimised. Abstract.The rate of zero-valent iron (ZVI) mediated reduction of CrVI was dependent on the condition of the ZVI surface, the pH of the medium and on the presence of inorganic oxyanions that can interfere with the process by competing for active sites on the ZVI surface. Whereas at pH 2, a single exponential decay provided an acceptable fit to the data, for pH 6 an appreciably better fit to the data was obtained with the sum of two exponential decays. The surface area normalised rate constant (kSA1) corresponding to the first decay was considered to model reactions at exposed active sites and kSA2, corresponding to the second decay, was considered to model decomposition kinetics through an intervening oxyhydroxide layer above the ZVI surface. The rate of CrVI reduction was decreased ∼900-fold when the pH was increased from 2 to 6 in the absence of competing ions. At pH 2, interferences from the major components of soil solution (nitrate, silicate and sulfate) were minimised.

Locating Al in the DABCO catalyst before and after Al extraction

1990 ◽  
Vol 48 (4) ◽  
pp. 265-267
Author(s):  
Kathleen B. Reuter
Keyword(s):  
Active Site ◽  
Inverse Relationship ◽  
Transverse Direction ◽  
Reaction Rate ◽  
Acid Phosphate ◽  
Fracture Surfaces ◽  
Al Content ◽  
Before And After ◽  
Relationship Of

The reaction rate and efficiency of piperazine to 1,4-diazabicyclo-octane (DABCO) depends on the Si/Al ratio of the MFI topology catalysts. The Al was shown to be the active site, however, in the Si/Al range of 30-200 the reaction rate increases as the Si/Al ratio increases. The objective of this work was to determine the location and concentration of Al to explain this inverse relationship of Al content with reaction rate.Two silicalite catalysts in the form of 1/16 inch SiO2/Al2O3 bonded extrudates were examined: catalyst A with a Si/Al of 83; and catalyst B, the acid/phosphate Al extracted form of catalyst A, with a Si/Al of 175. Five extrudates from each catalyst were fractured in the transverse direction and particles were obtained from the fracture surfaces near the center of the extrudate diameter. Particles were also obtained from the outside surfaces of five extrudates.

Direct observation of Fe-Al-Zn ternary intermetallic compound and its transformation during the early stage of hot-dip galvanizing

1993 ◽  
Vol 51 ◽  
pp. 1116-1117
Author(s):  
C. S. Lin ◽  
W. A. Chiou ◽  
M. Meshii
Keyword(s):  
Intermetallic Compound ◽  
Reaction Rate ◽  
Diffusion Rate ◽  
Early Stage ◽  
Zinc Bath ◽  
Steel Sheets ◽  
Direct Observations ◽  
Solid Iron ◽  
Iron And Zinc ◽  
Ternary Intermetallic Compound

The galvannealed steel sheets have received ever increased attention because of their excellent post-painting corrosion resistance and good weldability. However, its powdering and flaking tendency during press forming processes strongly impairs its performance. In order to optimize the properties of galvanneal coatings, it is critical to control the reaction rate between solid iron and molten zinc.In commercial galvannealing line, aluminum is added to zinc bath to retard the diffusion rate between iron and zinc by the formation of a thin layer of Al intermetallic compound on the surface of steel at initial hot-dip galvanizing. However, the form of this compound and its transformation are still speculated. In this paper, we report the direct observations of this compound and its transformation.The specimens were prepared in a hot-dip simulator in which the steel was galvanized in the zinc bath containing 0.14 wt% of Al at a temperature of 480 °C for 5 seconds and was quenched by liquid nitrogen.

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