Sulphuric sulphides

Weaver MJ, Inman D (1975) The sulphur-sulphide electrode in molten salts-1 Chronopotentiometric behaviour in lithium chloride-potassium chloride eutectic. Electrochim Acta 20 929-936... 

Many substances which are used for firework composition more or less have an influence upon the time of consolidation sulphur, sulphide or organic fuels particularly delay the consolidation. 

Amino-/iminoamino-phosphines, cyclotriphosphazene and other P - N Sulphur Sulphides (S)... 

A substantial amount of oxygen is expended for oxidizing sulphur. A larger portion of sulphur comes from rock minerals as native sulphur, sulphides and abiogenic H S and smaller part, as biogenic S or H S. Oxidizing these compounds is accompanied by loss of electrons up to the formation of sulphates ... 

It is now known that the effect of molybdenum is complex, and it is considered that the element exerts its limiting effect on copper retention in the animal only in the presence of sulphur. Sulphide is formed by ruminal microoiganisms from dietary sulphate or organic sulphur compounds the sulphide then reacts with molybdate to form thiomolybdate, which in turn combines with copper to form an insoluble copper thiomolybdate (CUM0S4), thereby limiting the absorption of dietary copper. In addition, it is considered likely that if thiomolybdate is formed in excess, it may be absorbed from the digestive tract and exert a systemic effect on copper metabolism in the animal. 

Prokof ev [18] studied the effects of oligomeric polysulphides on the rate of sulphidation of copper foil in m-xylene. These oligomers contained linear polysulphide chains. It was reported that the polysulphides themselves did not sulphidise the copper at an appreciable rate. However, when used together with elemental sulphur, sulphidation occurred and the sulphide was more homogeneous and finer than by sulphur alone. These results were used to explain the more stable bonding to rubber containing polysulphides. Apparently, linear sulphides are not reactive but they insert sulphide and then become active for sulphidation. 

Sulphur dioxide, SO2, m.p. — 72-7°C, b.p. — I0"C. Colourless gas with characteristic smell. Formed by burning S, metal sulphides, H2S in air or acid on a sulphite or hydrogen sulphite. Powerful reducing agent, particularly in water. Dissolves in water to give a gas hydrate the solution behaves as an acid - see sulphurous acid. Used in the production of SO3 for sulphuric acid. 

Gases which are high in FIjS are subject to a de-sulphurisation process in which H2S is converted into elemental sulphur or a metal sulphide. There are a number of processes based on absorption in contactors, adsorption (to a surface) in molecular sieves or chemical reaction (e.g. with zinc oxide). 

Potassium chloride actually has the same stnicture as sodium chloride, but, because the atomic scattering factors of potassium and chlorine are almost equal, the reflections with the indices all odd are extremely weak, and could easily have been missed in the early experiments. The zincblende fonn of zinc sulphide, by contrast, has the same pattern of all odd and all even indices, but the pattern of intensities is different. This pattern is consistent with a model that again has zinc atoms at the comers and tlie face centres, but the sulphur positions are displaced by a quarter of tlie body diagonal from the zinc positions. 

Arsenates(V) are more powerful oxidising agents than phos-phates(V) and will oxidise sulphite to sulphate, hydrogen sulphide (slowly) to sulphur and, depending on the conditions, iodide to iodine. 

Large deposits of free sulphur occur in America, Sicily and Japan. Combined sulphur occurs as sulphides, for example galena, PbS, zinc blende, ZnS, and iron pyrites, FeSj, and as sulphates, notably as gypsum or anhydrite, CaS04. 

Large quantities of sulphur are recovered from petroleum and natural gas. Naturally occurring hydrogen sulphide, HjS, and that produced in the cracking and catalytic hydrogenation of petroleum is first removed by absorption and the regenerated gas is converted to sulphur by partial combustion with air, the overall reaction being,... 

Oxygen does not read with alkalis. Sulphur dissolves slowly in strong alkalis to give a mixture of sulphite [sulphate(IV)] and sulphide initially ... 

However, the sulphide ion can attach to itself further atoms of sulphur to give polysulphide ions, for example Sj , Sj , and so these are found in solution also. Further, the sulphite ion can add on a sulphur atom to give the thiosulphate ion, S203 which is also found in the reaction mixture. 

Sulphur is less reactive than oxygen but still quite a reactive element and when heated it combines directly with the non-metallic elements, oxygen, hydrogen, the halogens (except iodine), carbon and phosphorus, and also with many metals to give sulphides. Selenium and tellurium are less reactive than sulphur but when heated combine directly with many metals and non-metals. 

In addition to the hydrides of formula HjX, oxygen forms the hydride H2O2, hydrogen peroxide, and sulphur forms a whole series of hydrides called sulphanes. These are yellow liquids which are thermodynamically unstable with respect to hydrogen sulphide and sulphur. 

Sulphur can be reduced directly to hydrogen sulphide by passing hydrogen through molten sulphur the reversible reaction H2 -I-S H2S occurs. In the laboratory the gas is most conveniently prepared by the action of an acid on a metal sulphide, iron(II) and dilute hydrochloric acid commonly being used ... 

Hydrogen sulphide bums in air with a blue flame yielding sulphur dioxide, but if the air supply is limited, preferential combustion to form sulphur occurs ... 

Hence the orange colour of a dichromate is converted to the green colour of the hydrated chromium(III) ion, Cr ", and sulphur is precipitated when hydrogen sulphide is passed through an acid solution.)... 

Since the hydrogen-element bond energy decreases from sulphur to tellurium they are stronger acids than hydrogen sulphide in aqueous solution but are still classified as weak acids—similar change in acid strength is observed for Group Vll hydrides. 

These are ionic solids and can exist as the anhydrous salts (prepared by heating together sulphur with excess of the alkali metal) or as hydrates, for example Na2S.9HjO. Since hydrogen sulphide is a weak acid these salts are hydrolysed in water,... 

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