Sulphides : characteristic chemical

Electronic conductance is characteristic for the so called conductors of the first class, i. e. for metals (both in solid and fused state) and some metal oxydes, carbides, sulphides, phosphides and borides and it can be explained by assuming the existence of free electrons which act in solid matter as anions. Under the influence of the external electric field these easily movable electrons start an ordered motion while the atoms deprived of their electrons, which are in fact cations, take practically no part in the current conduction and, apart from their vibration within the mean equilibrium positions, remain practically immobile. The passage of the current does not manifest itself by a chemical change of the... 

Filter out the precipitate and wash it on the filter paper with hot water until the filtrate is only faintly acid. Eest the funnel in a clean test tube, poke a hole in the tip of the filter paper, and wash the precipitate through into the test tube with 5 c.c. of ammonium sulphide. (11) What has happened to the precipitate (12) Write an equation for a hypothetical reaction between one molecule of arsenious oxide and three molecules of sodium oxide. (13) Write beneath this equation a similar one in which sulphur is substituted for oxygen and the ammonium radical for sodium. (14) For what reaction which you have carried out is this the equation (15) What chemical characteristic of arsenic is the cause of this reaction ... 

Since the lead smelter owned by OAO Kazzinc has ten years of experience in smelting lead-zinc sulphide concentrates by the Kivcet technology, a method of comparing physical and chemical properties of the bulk concentrate to the characteristics of typical lead-zinc raw materials has been developed. This method was used to decide on the feed composition and process operating conditions. Two major features of the bulk concentrate that affect the results of the smelting in the Kivcet unit were examined the calorific value and the desulphurization rate. 

Combination of more exnaction instfuments, that is, their successive use on the same sample, had first been applied by Gibbs [81], in the course of examination of suspended river material, and afterwards this method, with various modifications and improvements, was used by a number of authors, amongst whom probably the best known are Tessier [82, 83] and Foersmer [84-87], Very quickly the authors adopted the division into phases, which logically ensues from chemical characteristics of applicable extraction instruments, in other words, extraction instruments which meet the criteria of efficiency and selectivity to the maximum. Under phases here are implied discrete physical phases of geological material (i.e. silicate, oxide, carbonate, sulphide, organic phase, as well as fractions of heavy metals associated with them) whilst in the case of non-selectively bound metals an expression sorptive or exchangeable phase. 

The Ryton polyphenylene sulphide compounds are formulated for the encapsulation of semiconductors and discrete components and are particularly suited to this application because of their excellent thermal stability, resistance to chemical environments, flame retardancy and good electrical properties over a wide temperature range. In order to be suitable for the encapsulation of microcircuits and transistors the material must have good flow during moulding, good dimensional stability, low levels of impurities and low moisture absorption characteristics. 

Chemically, the microporous material is composed of a mixture of oxides - and in less proportion of sulphides - of the main elements present in the-substrate and of the alloy itself. Minority elements are also present as dopants. There is a composition gradient from the support up to the surface where the metallic element are entirely in the combined state. In general by adjusting the nature of the substrate alloy and the conditions of treatment it is possible to modify the characteristics of the catalysts. 

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