Flammability Limits of an Oxidation Reaction in a Batch Reactor. II. The Rychlý Mechanism

It is often numerically convenient to reduce models in two-dimensions to one-dimension. This can be done formally through the use of centre manifold techniques, or informally using physical reasoning. We investigate the extent to which flammability limits in a two-dimensional slab are accurately represented by the values in the corresponding one-dimensional slab. We use a simple chemical mechanism containing exothermic and endothermic reactions that has been used to model the combustion of hydrocarbon fragments produced by polymer pyrolysis.     

Syntheses and interconversions of some s-triazolo[3,4-a]isoquinolines

s-Triazolo[3,4-a]isoquinoline (II) and its 3-methyl analogue (III) have been synthesized from 1-isoquinolylhydrazine (I) by cyclisation with formic and acetic acid. The 3-hydroxy derivative (IV) has been shown to exist in the lactam form. Methylation with methyl iodide gave the N-methyl derivative (V). Dimethyl sulphate and diazomethane also led exclusively to the same product. The O-methyl derivative (IX) could be obtained only through the 3-chloro compound (VIII). The chlorine atom in VIII undergoes nucleophilic replacement easily. The 3,6-dichloro derivative (X) has also been prepared. Several interconversions in the series are described. Aryl hydrazones (XVIII) prepared from (I) have been oxidatively cyclised to give 3-aryl-s-triazolo[3,4-a]isoquinolines (XIX). U.V., I.R. and P.M.R. spectra have been recorded and used for assignment of structures in some cases.     

A new colorimetric method for the determination of carbon disulphide and its application to the analysis of some dithiocarbamate fungicides

A new and convenient colorimetric method for determination of carbon disulphide, based on its transformation into bright yellow potassium benzyl trithiocarbonate through reaction with benzyl mercaptan and potassium hydroxide in tert.-butyl alcohol, has been successfully applied to determination of some dithiocarbamate fungicides in their formulations. The method possesses a distinct advantage in that it is free from all sources of errors/problems which are associated with the xanthate method for the analysis of these materials. The proposed method is precise and accurate and hence recommended for routine analysis of technical formulations containing dithiocarbamate fungicides.     

Structure investigations by P.A.C.

The perturbed angular correlation /P.A.C./ technique is employed to investigate the structures of barium ferrite and barium hexaferrite using radioactive¹³³Ba /10.7 Y/ as a probe. The quadrupole interaction frequencies /W_Q'S/ are found to be 9.68 and 12.02 Mrad sec^–1 for barium ferrite and barium hexaferrite, respectively, showing a drift from usual cubic structure.     

Photochemical reduction of uranyl ion with ditertiary phosphines in dry acetone

Time-resolved transient absorption spectra have been observed using monochromatic light (=347.1 nm) from a 25 ns pulsed ruby laser. Collision between optically excited uranyl ion and ditertiary phosphines lead to photochemical reduction of uranyl ion to uranium(V) in non-aqueous medium. Stern-Volmer constants measured from lifetime measurement and quantum yields for uranium(V) formation reveal that electron transfer phenomenon competes with photophysical deactivation because of the presence of phenyl groups. Since ditertiary phosphines have two electron donating phosphorus atoms, are better reductant than monodentate phosphines in non aqueous medium.     

Determination of isoniazid and hydrazine by capillary electrophoresis with amperometric detection at a Pt-particle modified carbon fiber microelectrode

Capillary electrpphoresis (CE)/electrochemical detection (EC) for the simultane-ous determination of hydrazine and isoniazid has been developed.The electrochemical method uses a novel modified electrode dispersed with ultrafine platinum particles on the surface of a 30μm carbon fiber microelectrode.The unique characteristic of the Pt-particles modified carbon fiber microelectrode is its excellent stability.The current measurement for hydrazine is more sensitive than that of isoniazid.Selective determination of trace amount of free hydrazine in isoniazid and its formulation can be achieved at applied potential of 0.5V.     

Trace element analysis of hair of mentally retarded children

Unlike previously reported Zn and Se levels were found to be the same in the hair of mentally retarded children and controls. Non-essential toxic Ag concentration was low whereas that of Hg, Au and Sc rather high in mentally retarded children.     

Analytical applications of mercaptan-carbon disulphide reaction: Determination of mixtures containing mercaptans

Summary A method is described for the determination of mercaptans by alkalimetric titration of trithiocarbonic acids formed through their reaction with carbon disulphide in tert.-butanol. The method has been applied to the analysis, on the same sample solution, of mixtures of mercaptans containing titrable hydrogen and those containing nontitrable hydrogen, mercaptans and alkali mercaptides, and mercaptans and mercaptopyrimidines.

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Analytische Anwendung der Merkaptan-Schwefelkohlenstoff-Reaktion: Bestimmung von Merkaptan in Gemischen

Zusammenfassung Ein Verfahren zur Merkaptanbestimmung durch alkalimetrische Titration der Trithiokohlensäure auf der Grundlage seiner Reaktion mit Schwefelkohlenstoff in tert. Butanol wurde beschrieben. Es eignet sich zur Bestimmung von Gemischen aus Merkaptanen mit titrierbarem Wasserstoff und solchen ohne titrierbaren Wasserstoff sowie von Merkaptanen und Merkaptiden, weiters von Merkaptanen und Merkaptopyrimidinen.

     

Analysis of a Chemostat Model with Variable Yield Coefficient

We investigate a chemostat model in which the growth rate is given by a Monod expression with a variable yield coefficient. This model has been investigated by previous researchers using numerical integration. We combine analytical results with path-following methods. The conditions for washout to occur are found. When washout does not occur we establish the conditions under which the reactor performance is maximised at either a finite or infinite residence time. We also determine the parameter region in which oscillations may be generated in the reactor, which was the primary feature of interest to earlier workers on this problem.