The general theory of polarographic kinetic currents

A unified mathematical formulation of the transport problem to the dropping electrode, accounting for diffusion, chemical reactions in solution and electrode reactions, is given. The method for the reduction of the problem to a diffusion problem where the effect of chemical reactions is restricted to boundary conditions is described. Conditions are defined for appearance of a kinetic current and, on the contrary, of a diffusion current dependent on equilibrium constants of chemical reactions. The general results are exemplified by the case of a single chemical and a single electrode reaction.     

How graphical analysis helps interpreting optimal experimental designs for nonlinear enzyme kinetic models

Progress curve experiments combined with optimal experimental design (OED) are an efficient approach to determine enzyme kinetics. However, it is hardly possible to verify why specific experiments are suggested for nonlinear enzyme kinetic model identification. Therefore, we systematically investigated the surface and contour plots of the sensitivities and of the OED criteria which are based on sensitivities. The model reaction was an enzyme catalyzed self‐ligation of aldehydes to chiral 2‐hydroxyketones. The visualization improved the understanding of OED and allowed for deducing and confirming five suggestions for kinetic identification: (1) Avoid experiments vicinal to the reaction equilibrium, (2) Choose the design space as large as possible, (3) Prefer D(eterminant)‐ and E(igenvalue)‐criteria over the A(verage)‐criterion, (4) Apply enzyme concentrations such that the reaction does not complete too fast, and (5) Few optimal experiments result in significantly improved parameter estimations. The graphical analysis also provides information about selecting appropriate optimization algorithms. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

Reactor design from batch data by a direct graphical method

A graphical method for reactor design is presented which uses the plot of concentration vs. time. This method can be used to compare stirred tank, plug flow and recycle reactors as well as various reactor combinations. With Monod Kinetics the concept of wash-out can be illustrated. A brief comparison with other graphical methods is made.     

A graphical approach to causes and effects analysis of chemical processing systems

An original method developed for solving the problem of locating the origin of a system failure on the concept of a signed digraph has been extensively applied to the cause and effect analysis of chemical processing systems, whose mathematical models are expressed by differential equations. As an illustrative example, a propane vaporizer has been taken up to show the usefulness of the present approach.     

A graphical approach to cause and effect analysis of chemical processing systems

A method for cause and effect analysis of chemical processing systems has been developed on the concept of a signed directed graph. The signed directed graph, called a “model graph,” is used for representing cause and effect relationships among process variables in a system, and a “Pattern” on the graph is introduced to represent a state of the system, which is specified by “0” for normal state, “ + ” and “ ? ” for larger and smaller deviation from the normal state, respectively. For a given model graph and pattern on it, the cause of state changes and the manner of their propagation are easily found out by the present approach, which is mainly based on the depth-first search algorithm developed by Tarjan. As an illustrative example, a propane vaporizer has been taken to show the usefulness of the present approach.     

Radiation-induced grafting onto wool. A kinetic analysis

The radiation-induced graft copolymerization of styrene onto wool in aqueous methanol was studied over a temperature range of 0°C to 45°C and a radiation dose-rate range of 0.05 to 2.0 Mrad/hr. The rate of grafting was found to obey the classical polymerization equation. Chain transfer to wool was found to play an important role in the grafting process, and the molecular weight of the resulting graft copolymer was found to be independent of the irradiation dose. The activation energy of the graft process changed from a value of 4.7 kcal/mole below 19°C to a value of 18.7 kcal/mole above this temperature. This phenomenon is ascribed to the formation of hydrogen-bonded systems between the protic solvent molecules and the protein chain in the wool.     

Moment analysis of nonlinear systems: A kinetic study

The moment method has been used extensively to evaluate parameters of chemical reactions, adsorption or reactor design, but only for linear systems. Moment analysis of nonlinear systems is studied in the present work. A general complicated reaction system involving nonlinear terms in a batch slurry reactor is chosen to demonstrate the method. The first and second improved solutions in Laplace domain and moment expressions are obtained. The improved solution can converge to the exact solution if the iterative procedures are repeated several times.     

用于反应精馏过程可行性分析的立体图解法

开发了一种用于反应精馏可行性分析和概念设计研究的新方法—立体图解法,该方法创新之处在于温度参数的加入,解决了传统判断方法中无法考虑温度因素的难题.立体图解法依据研究体系的气液相平衡方程和反应平衡方程得到泡点曲面和反应平衡曲面,进而得到精馏边界及反应精馏曲线.依据目标产物的质量分数在立体图中画出反应精馏路径,分析体系反应精馏过程的可行性,同时得到初步概念设计的相关信息,如反应精馏是否需要精馏段和提馏段、反应精馏过程可行的进料组成范围、进料位置等.以假定的通式化三元反应体系阐述立体图解法的应用方法及普适性.通过与传统平面图解法的对比,得出该立体图解法能够更加准确地计算反应精馏过程可行的进料组成范围.     

A polarographic study of some complexes of molybdenum

The catalytic current due to the reduction of perchlorate by Mo (IV) or of nitrate by Mo(III) can be decreased by complexing these molybdenum species. When only one complex forms, the instability constant and the ratio of complexing agent to molybdenum can be evaluated. When the catalytic waves are completely suppressed, only the normal polarographic waves appear. The latter can be used to determine molybdenum quantitatively without the necessity of a calibration curve.     

A kinetic analysis of the exchange of deuterium with hydrides

In the exchange reaction between deuterium and hydride molecules, the consecutive single-step mechanism is characterized by interactions only between the ith deutero-isomer and the (i + 1) and (i − 1) isomers. Rate equations have been set up on this basis and their exact and unique solutions found. This permits the deutero-isomer distribution to be expressed analytically as a function of the time. If the initial state contains only undeuterated hydride or a binomial distribution of isomers, the distribution has been shown to maintain its binomial character to equilibrium.An application of the analysis to two exemplary cases has been made.     

A kinetic analysis of the thermal-oxidative decomposition of expandable polystyrene

The kinetics of the thermal-oxidative decomposition of expandable polystyrene (EPS) was studied by a conventional thermogravimetric technique in various concentrations of oxygen from 0 to 21%. A kinetic model that accounts for the effects of oxygen concentration was proposed to describe the thermal-oxidative decomposition of EPS. The thermogravimetric analysis curve and its derivative have been analyzed by using differential and integral methods with modification of the Friedman and Coats-Redfern methods. The activation energy, the pre-exponential factor, and the reaction order for unreacted material and oxygen concentration have been determined. When oxygen was present, the activation energy was reduced significantly.     

A direct volumetric method for the analysis of soap

Summary Glycol, or preferably its mixture with a solvent for hydrocarbons, such as isopropyl alcohol or chloroform, possesses high solvent power for soaps, which may be directly titrated with strong acids, either potentiometrically or with the use of methyl red or methyl orange. The ionization of the organic acid is suppressed so that salts of weak acids can be directly titrated by this method. The colors of the indicators are brighter and the end-point sharper than those in alcohol or water. Presented at the 19th Annual Fall Meeting of The American Oil Chemists’ Society, Nov. 7–9, 1945, in Chicago. Bristol-Myers Company post-doctorate fellow in chemistry.     

Supplementary graphical analysis for the multi-density expansion of associating fluids

We present a detailed analysis of Wertheim’s multi-density formulation for the thermodynamic properties of associating fluids with a single attraction site. Graphical expressions are explicitly illustrated for the partition function, multi-densities and direct correlation functions, and they are compared with those from the classical single-density formulation of simple fluids. The steric incompatibility among three monomers greatly simplifies cluster integrals of associating fluids, which allows dimerizing association only. Graphical expressions for the pressure and the Helmholtz energy are derived by using functional derivatives, which provide a theoretical base for TPT and SAFT equations of state.     

Measurement and differential kinetic analysis of wall temperatures in monolith converters—I kinetic analysis

It is possible to measure axial wall temperature profiles in adiabatic monolith converters under actual reaction conditions. By applying a differential method of kinetic analysis, axial profiles of concentrations at the wall as well as of reaction rates can be derived with proper computation methods. The data thus obtained may serve for further kinetic evaluation, that is for model building and parameter estimation by proven and well-known methods. The whole procedure looks also promising for performing activity tests on fresh and partly deactivated monolith converters. The slightly greater effort of measuring wall temperatures compared with the usual method only to record inlet and outlet temperatures and integral conversions might more than pay off. In the present first part of the paper the differential method of kinetic analysis is developed and tested by some simulation studies. The second part will deal with actual experiments.     

A direct method for regiospecific analysis of TAG using alpha-MAG

An analytical procedure was developed for regiodistribution analysis of TAG using α-MAG prepared by an ethyl magnesium bromide deacylation. In the present communication, the deacylation procedure is shown to lead to representative α-MAG, allowing the composition of the native TAG in the α-position to be determined directly. The composition in the β-position can then be estimated from the composition of the α-MAG and TAG according to the formula, 3×TAG-2×α-MAG. The estimates are superior to those obtained using the α,β-DAG and Brockerhoff calculations as they come closer to the theoretical value and have smaller SD. The present procedure, first demonstrated on a synthetic TAG, was then successfully applied to the analysis of borage oil, milkfat, and tuna oil.