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1

The influence of chromium dopant of transport properties of [alfa]-MnS

Gilewicz-Wolter J., Grzesik Z., Wolter M., Dąbek J., Dudała J.

Bulletin of the Polish Academy of Sciences. Chemistry

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2003

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Vol. 51, No. 2

127-134

EN

The influence of chromium on self-diffusion of cations in metal-deficit man-ganous sulphide, Mn1_yS, has been studied as a function of temperature and sulphur activity, using radio-tracer technique. It has been found that the rate of Mn self-diffusion in chromium doped Mn1_yS is higher than that in pure manganous sulphide and does not depend on equilibrium sulphur pressure. In addition, the activation energy of self-diffusion in Mn1_yS-Cr2S3 solid solution is lower than that in pure Mn1_yS. Both these results are in agreement with theoretical predictions based on simple defect model in Mn1_yS, assuming that the predominant defects in this sulphide are non-interacting, doubly ionized cation vacancies and electron holes.

2

Thioammeline and thioammeline disulfide as analytical reagents. Determination of sulfides and cyanides

Kurzawa J., Janowicz K., Krzymińska A.

Chemia Analityczna

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2000

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Vol. 45, No. 2

265-271

EN

The application of thioammeline for the determination of traces of several species by the induced iodine-azide reaction is summarised. The methods are based on the estimation of the decrease in thioammeline concentration caused by the reaction with Cu2+, C12, la, and O3. The paper presents the results of application of thioammeline disulfide for the determination of sulfide and cyanide at the ng g-1 level. The method is based on the determination of thioammeline formed in the reaction of cleavage of the -S-S- bond in disulfide by S2- or CN-. The proposed method permits the determination of sulfide at concentration from 1.5 to 25 ug 1-1 and cyanides from 3 to 70 ug 1-1. The determination of both species in the presence of each other is also possible thanks to different influence of pH on the cleavage reaction.

PL

W pracy podsumowano zastosowanie tioameliny jako odczynnika do oznaczania Cu2+, Cl(2), I(2) i O(3). Oznaczenia te polegają na pomiarze za pomocą indukowanej reakcji jodo-azydkowej ilości tioameliny zużytej w reakcji kompleksowania lub utleniania. Oznaczenie za pomocą tej samej reakcji ilości tioameliny powstałej w wyniku reakcji rozszczepienia wiązania -S-S- w disiarczku tioameliny przez S2- lub CN- umożliwia oznaczanie tych jonów w zakresie od 1.5 do 25 ug1-1 jonów siarczkowych oraz od 3 do 70 ug1(-1) jonów cyjankowych. Ponieważ pH środowiska wpływa na przebieg reakcji rozszczepienia disiarczku możliwe jest współoznaczanie obu jonów bez konieczności ich selektywnego wydzielania z analizowanej próbki.

3

Mechanistic studies on the oxidation of some organic sulphides with quinolinium fluorochromate in nonaqueous medium

Meenakshisundaram S., Sathiyendiran V.

Bulletin of the Polish Academy of Sciences. Chemistry

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1999

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Vol. 47, No. 2

167-174

EN

The oxidation kinetics of diphenyl, dialkyl and methyl phenyl sulphides has been investigated under pseudo-first-order conditions with quinolinium fluorochromate (QFC), a newly developed Cr(VI) reagent in acetonitrile medium. p- Toluene sulphonic acid (TsOH) is used for catalyzing the reaction. Initial-rate methods are used for determining the orders with respect to reactants in dialkyl sulphides. The oxidation is first-order with respect to [QFC] and second-order dependence is observed on [TsOH]. [Sulphide] has no effect on the reaction rate. Diphenyl sulphide (DPS) oxidation follows the rate law, v = k2Rrl [S][Ox][TsOH]. Acrylonitrile retards the rate of oxidation significantly in diphenyl sulphides indicating the involvement of free radical cation sulphur intermediate in the rate-limiting step. The Michaelis-Menten dependence each on [sulphide] and [TsOH] can be well explained by a two-pathway mechanism in methyl phenyl sulphide oxidation. The derived rate law, v = k1[Ox][TsOH] -+ k3[OX][S] is consistent with experimental observations.