Hydrogen sulphide, reaction

Tin(IV) in aqueous acid gives a yellow precipitate with hydrogen sulphide, and no reaction with mercury(II) chloride. 

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,... 

Lead(II) sulphide is oxidised to lead(II) sulphate this reaction has been used in the restoration of old pictures where the white lead pigment has become blackened by conversion to lead sulphide due to hydrogen sulphide in urban air ... 

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 ... 

These two gases can readily be prepared by the action of acids on selenides and tellurides respectively, the reactions being analogous to that for the preparation of hydrogen sulphide. 

Many of the reactions of these acids, however, closely resemble those of hydrogen sulphide, the main difference being one of degree. 

Further reaction between hydrogen sulphide and the sulphite ion yields sulphur together with thionic acids) ... 

Bromine has many oxidising reactions ( = + 1.07 V) and like chlorine it will oxidise sulphur dioxide in aqueous solution to sulphuric acid, and hydrogen sulphide to sulphur. 

Copper(II) ions in aqueous solution are readily obtained from any copper-containing material. The reactions with (a) alkali (p. 430), (b) concentrated ammonia (p 413) and (c) hydrogen sulphide (p. 413) provide satisfactory tests for aqueous copper(II) ions. A further test is to add a hexacyanoferrate(II) (usually as the potassium salt) when a chocolate-brown precipitate of copper(II) hexacyanoferrate(II) is obtained ... 

In a 1 litre round-bottomed flask provided with an efficient double surface condenser, place 40 g. (39 ml.) of aniline, 50 g. (40 ml.) of carbon sulphide CAUTION inflammable) (1), and 50 g. (63-5 ml.) of absolute ethyl alcohol (2). Set up the apparatus in the fume cupboard or attach an absorption device to the top of the condenser (see Fig. 11, 8, 1) to absorb the hydrogen sulphide which is evolved. Heat upon an electrically-heated water bath or upon a steam bath for 8 hours or until the contents of the flask sohdify. When the reaction is complete, arrange the condenser for downward distillation (Fig. 11, 13, 3), and remove the excess of carbon disulphide and alcohol (CA UTION inflammable there must be no flame near the receiver). Shake the residue in the flask with excess of dilute hydrochloric acid (1 10) to remove any aniline present, filter at the pump, wash with water, and drain well. Dry in the steam oven. The yield of crude product, which is quite satisfactory for the preparation of phenyl iao-thiocyanute (Section IV.95), is 40-45 g. Recrystalhse the crude thiocarbanihde by dissolving it, under reflux, in boiling rectified spirit (filter through a hot water funnel if the solution is not clear), and add hot water until the solution just becomes cloudy and allow to cool. Pure sj/m.-diphenylthiourea separates in colourless needles, m.p, 154°,... 

A little hydrogen sulphide is evolved in the reaction and triphenylguanidine is formed as a by-product, probably in accordance with the following scheme ... 

Neutralization of strong mineral acids from metal finishing trades (sulphide and hypochlorite contamination common) Fierce reaction Possibility of mixing with water or organic materials Chlorine Nitrogen dioxide Sulphur dioxide Hydrogen sulphide... 

The mechanism of the Cook-Heilbron reaction between a-aminonitriles and dithioformic ester 6 proceeds via an acyclic intermediate 7, as proven by its isolation in several cases. Nucleophilic attack of the amine function on the sulfur-bearing carbon leads to the elimination of hydrogen sulphide. Cyclization of the acyclic thiacetoamide results in a five membered ring which aromatises favourably to give 5-amino-2-benzylthiazole 8. 

Copper tarnishes rapidly when exposed to atmospheres containing hydrogen sulphide and the reaction is not dependent on the presence of moisture. 

The corrosion of tin by nitric acid and its inhibition by n-alkylamines has been reportedThe action of perchloric acid on tin has been studied " and sulphuric acid corrosion inhibition by aniline, pyridine and their derivatives as well as sulphones, sulphoxides and sulphides described. Attack of tin by oxalic, citric and tartaric acids was found to be under the anodic control of the Sn salts in solution in oxygen free conditions . In a study of tin contaminated by up to 1200 ppm Sb, it was demonstrated that the modified surface chemistry catalysed the hydrogen evolution reaction in deaerated citric acid solution. 

Adsorbed species may also accelerate the rate of anodic dissolution of metals, as indicated by a decrease in Tafel slope for the reaction. Thus the presence of hydrogen sulphide in acid solutions stimulates the corrosion of iron, and decreases the Tafel slope The reaction path through... 

For reasonably satisfactory results, the sulphide solution must be dilute (concentration not greater than 0.04 per cent or 0.01M), and the sulphide solution added to excess of acidified 0.005M or 0.05M iodine and not conversely. Loss of hydrogen sulphide is thus avoided, and side reactions are almost entirely eliminated. (With solutions more concentrated than about 0.01M, the precipitated sulphur encloses a portion of the iodine, and this escapes the subsequent titration... 

Hydrogen sulphide occurs naturally, e.g. in natural gas and petroleum, volcanic gases, and from decaying organic matter. It may be present near oil wells and where petroleum is processed. Commercially it is obtained as a by-product from many chemical reactions including off-gas in the production of some synthetic polymers (e.g. rayon, nylon) from petroleum products, and by the action of dilute mineral acids on metal sulphides. Physical properties are summarized in Table 9.14 and effects of temperature on vapour pressure are shown in Figure 9.5. 

The reaction between [Cl3P=N-PCy BCU" and hydrogen sulphide was also straightforward ... 

A reaction between sodium from the glass and atmospheric water and carbon dioxide can lead to the formation of sodium carbonate, which crystallizes in fine needles. A potash glass forms potassium carbonate, which is too deliquescent to crystallize out. A lead glass can react with hydrogen sulphide, and to a smaller extent with carbon dioxide, sulphur dioxide, and acid vapoiurs. 

The formation of hydrogen sulphide produces -20.6/2 kj ie -10.3 kj per hydrogen atom whereas the formation of methane produces -74.82/4 kJ ie -18.705 kJ per hydrogen atom. Maximum methane has then to be formed in this hypothetical reaction. To be thorough, the potential formation of carbon disulphide has to be analysed, but this substance is endothermic. ... 

Hydrogen sulphide combusts spontaneously in the presence of oxygen when the mixture is at a temperature of 280-360 . Under controlled conditions this reaction is used to make suiphur from hydrogen sulphide. When soda lime is present, the interaction with pure oxygen is explosive whereas air simply causes soda lime to glow. 

Lead peroxide is even more active than the oxide. It reacts violently with sulphur and sulphides. When it is ground up with sulphur, the mixture combusts. With hydrogen sulphide, the reaction is very exothermic and causes peroxide to incandesce and hydrogen sulphide to combust. Finally, it reacts violently with calcium, strontium and barium sulphides on heating. 

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