Hydrogen Sulphide formation

The basic reaction of amino acids under irradiation conditions is the formation of a radical intermediate on the a-carbon atom. From this, ketoacids, iminoacids and degradation products are formed (Scheme 7.3). Cysteine is decomposed to cystine, with hydrogen sulphide formation causing the off flavour of irradiated protein-rich products. 

Corrosion service Carbon dioxide (CO2) or hydrogen sulphide (H2S) in formation tluids will cause rapid corrosion of standard carbon steel and special steel may be required... 

If produced gas contains water vapour it may have to be dried (dehydrated). Water condensation in the process facilities can lead to hydrate formation and may cause corrosion (pipelines are particularly vulnerable) in the presence of carbon dioxide and hydrogen sulphide. Hydrates are formed by physical bonding between water and the lighter components in natural gas. They can plug pipes and process equipment. Charts such as the one below are available to predict when hydrate formation may become a problem. 

These gases have lower thermal stabilities than hydrogen sulphide as expected from their enthalpies of formation Table 10.2) and they are consequently more powerful reducing agents than hydrogen sulphide. 

Lead formate separates from aqueous solution without water of crystallisation. It can therefore be used for the preparation of anhydrous formic acid. For this purpose, the powdered lead formate is placed in the inner tube of an ordinary jacketed cond ser, and there held loosely in position by plugs of glass-wool. The condenser is then clamped in an oblique position and the lower end fitted into a receiver closed with a calcium chloride tube. A current of dry hydrogen sulphide is passed down the inner tube of the condenser, whilst steam is passed through the jacket. The formic acid which is liberated... 

HCOO)2Pb + H2S 2HCOOH + PbS. collects in the receiver, and is th i purified from dissolved hydrogen sulphide by redistillation over a further quantity of lead formate. 

Arsenic. The presence of arsenie in an organie eompound is generally revealed by the formation of a dull grey mirror of arsenic on the walls of the test-tube when the eompound is fused with sodium in the Lassaigne teat. Usually sufficient arsenic is found in the fusion solution to give a yellow precipitate of arsenic trisulphide when the solution is acidified with hydrochloric acid and treated with hydrogen sulphide. 

The product crystals find industrial application as a component raw material for optical glass, fibreglass, Braun tubes, electric condensers, barium ferrite, etc. Needles shaped crystals are obtained at high pH, while pillar-shaped crystals are formed at neutral pH. The formation of carboxyl ions is via hydroxy ions at high pH, but at neutral pH it may accompany the production of hydrogen sulphide, as... 

The tarnishing of copper and silver in dry air containing traces of hydrogen sulphide (Table 2.6) is another example of film growth by lattice diffusion at ambient temperatures. In these cases defects in the sulphide lattice enable the films to grow to visible thicknesses with the consequent formation of tarnish films which are aesthetically objectionable and may have a significant effect on the behaviour of the metals in particular applications, e.g. electrical contacts. 

Natural sea water is well buffered and normally lies between 8 1 and 8 3 but may fall to 7-0 in stagnant basins with the formation of hydrogen sulphide produced by anaerobic bacteria. 

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. ... 

Some bacteria can give products a rancid smell others can impart the "sweet" odour of dirty drains by the production of certain pyrazine derivatives. Other bacteria, known as sulphate reducers, for example Desulphovibrio desulphuricans, are able, under anaerobic conditions, to utilise oxygen from sulphates leading ultimately to the formation of hydrogen sulphide. Opperman and Goll (1984) in their study of contaminated emulsion paints concluded that more than a quarter were infected with these and other anaerobic organisms. 

The oxidative formation of pyrite from iron and hydrogen sulphide supplied the reduction equivalents vital for the fixation of the carbon to be used in the synthesis of key molecules from simple building blocks (such as CO or CO2). 

The hydrolytic breakdown of the disulphide bonds of cystine liberates some hydrogen sulphide and this can gradually deactivate a vinylsulphone dye by formation of the... 

Doctor et al. (2000) point out the technical problems in the transport infrastructure that could arise from impurities in the C02. Any transport system requires the C02 to be dried to prevent the formation of C02 hydrates. Considerable problems with the formation of iron sulphide in natural gas pipelines indicate that C02 also has to be cleaned of hydrogen sulphide content. 

If the oxidation which leads to the formation of Bindschedler s green takes place in the presence of hydrogen sulphide the process is varied by the entrance of sulphur. In principle, however, the mechanism is the same as before. The following formulae show that an addition of H—8H and a subsequent intramolecular addition of a mercaptan group are stages in the reaction ... 

In contrast with the reactions involving sulphide or hydrogen sulphide anions, aryl alkyl thioethers and unsymmetrical dialkyl thioethers (Table 4.3) are obtained conveniently by the analogous nucleophilic substitution reactions between haloalkanes and aryl or alkylthiols under mildly basic conditions in the presence of a quaternary ammonium salt [9-15] or polymer-supported quaternary ammonium salt [16]. Dimethyl carbonate is a very effective agent in the formation of methyl thioethers (4.1.4.B) [17]. 

In any case, covering may be impracticable for other reasons. Many processes as they are currently designed depend upon at least visual access by operators for process control, and in other instances the production of odorous chemicals such as hydrogen sulphide can be accompanied by the formation of methane, giving a potential fire or explosion hazard. 

The interaction of biguanide (CL) and isothiocyanate esters in dimethyl-formamide under mild conditions (376) gives excellent 3delds of 1-sub-stituted hexahydro-4,6-di-imino-s-triazine-2-thiones (CLII), together with small quantities of thioammeline (CLIII) and monosubstituted melamines (CLIV). Under more severe conditions, the latter (CLIV) become the main products. The production of these triazines is explained by a mechanism involving the primary formation of addition products (CLI), followed by their cydisation with loss of either ammonia, hydrogen sulphide, or primary amine (376). 

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