Hydrogen sulphide methods

Hydrogen Sulphide Method Compounds containing carboxyl liberate hydrogen sulphide from certain metallo-hydrogen sulphides when allowed to react in an atmosphere of hydrogen sulphide, according to flie equation ... 

Watson et al. (15) essentially improved the hydrogen sulphide method by cleaning and storing the acid for the decomposition in the same closed apparatus and by keeping the distillation apparatus as small as possible and combining it directly with the acid stock bottle. The hydrogen sulphide can be determined as well titrimetrically as photometrically. 

When an organic compound is heated with a mixture of zinc powder and sodium carbonate, the nitrogen and halogens are converted into sodium cyanide and sodium hahdes respectively, and the sulphur into zinc sulphide (insoluble in water). The sodium cyanide and sodium hahdes are extracted with water and detected as in Lassaigne s method, whilst the zinc sulphide in the residue is decomposed with dilute acid and the hydrogen sulphide is identified with sodium plumbite or lead acetate paper. The test for nitrogen is thus not affected by the presence of sulphur this constitutes an advantage of the method. 

Ultramodern techniques are being applied to the study of corrosion thus a very recent initiative at Sandia Laboratories in America studied the corrosion of copper in air spiked with hydrogen sulphide by a form of combinatorial test, in which a protective coat of copper oxide was varied in thickness, and in parallel, the density of defects in the copper provoked by irradiation was also varied. Defects proved to be more influential than the thickness of the protective layer. This conclusion is valuable in preventing corrosion of copper conductors in advanced microcircuits. This set of experiments is typical of modern materials science, in that quite diverse themes... combinatorial methods, corrosion kinetics and irradiation damage... are simultaneously exploited. 

In electrochemical cells sample oxidation produces an electric current proportional to the concentration of test substance. Sometimes interferences by other contaminants can be problematic and in general the method is poorer than IR. Portable and static instruments based on this method are available for specific chemicals, e.g. carbon monoxide, chlorine, hydrogen sulphide. 

Neuberg and Tiemann propose the following method, depending on the fact that most aldehydes form a compound with thiosemi-car-bazide. The oil containing aldehyde is heated in alcoholic solution on a water-bath, with thiosemi-carbazide. Various salts of the heavy metals will form insoluble precipitates with the thiosemi-carbazone formed, and such precipitate is dissolved in alcohol, and a current of hydrogen sulphide passed through until the metal is precipitated, leaving the thiosemi-carbazone dissolved in the alcohol. 

Excellent results are obtained by the following method, which is of wider applicability. When excess of standard sodium arsenite solution is treated with hydrogen sulphide solution and then acidified with hydrochloric acid, arsenic(III) sulphide is precipitated ... 

Antimony pyrogallate, Sb(C6H503). Antimony(III) salts in the presence of tartrate ions may be quantitatively predpitated with a large excess of aqueous pyrogallol as the dense antimony pyrogallate. The method fadlitates a simple separation from arsenic the latter element may be determined in the filtrate from the predpitation of antimony by direct treatment with hydrogen sulphide. 

Florin THJ. 1991. Hydrogen sulphide and total acid-volatile sulphide in feces, determined with a direct spectrophotometric method. Clin Chim Acta 196 127-134. 

A method of vulcanising thin rubber articles, now of historical interest only. The products are exposed successively to the gases, sulphur dioxide and hydrogen sulphide, which react to form active sulphur which brings about vulcanisation. 

Two basic methods are used for the manufacture of sulphur dyes. In one, the starting materials are baked either with sulphur alone or with sulphur and sodium sulphide at a temperature between 180 and 350 °C. Alternatively the intermediates are heated under reflux in aqueous or alcoholic sodium polysulphide this process may also be carried out under pressure at temperatures up to about 130 °C. Following sulphurisation the dye is precipitated by means of air or chemical oxidation, acidification or a combination of these methods. The sulphurisation process results in the evolution of hydrogen sulphide, which is usually absorbed in aqueous sodium hydroxide for use elsewhere - in the reduction of nitro compounds, for example. 

Various workers [52, 105, 108] have modified these procedures to improve precision, by employing zinc sulphide as a standard in contrast to the sodium sulphide solution used in earlier methods. The addition of sodium hydroxide to the hydrogen sulphide absorption solution improves recovery. 

Kupec et al. [180] determined total sulphur in sludge by a method involving magnesium reduction in which the sample is heated with magnesium powder to convert all sulphur compounds into magnesium sulphide. The magnesium sulphide is treated with sulphuric acid and the evolved hydrogen sulphide determined by iodometric titration. 

Sulphur, ozone and hydrogen sulphide were investigated as possible causes for the interference. No interference was observed. When the automated method was used, the interferences which were observed for the standards and blank spiked with lOOmg sulphide L-1, occurred when an excess of dichromate did not exist in the solutions. 

As esters the alkyl halides are hydrolysed by alkalis to alcohols and salts of halogen acids. They are converted by nascent hydrogen into hydrocarbons, by ammonia into amines, by alkoxides into ethers, by alkali hydrogen sulphides into mercaptans, by potassium cyanide into nitriles, and by sodium acetate into acetic esters. (Formulate these reactions.) The alkyl halides are practically insoluble in water but are, on the other hand, miscible with organic solvents. As a consequence of the great affinity of iodine for silver, the alkyl iodides are almost instantaneously decomposed by aqueous-alcoholic silver nitrate solution, and so yield silver iodide and alcohol. The important method of Ziesel for the quantitative determination of alkyl groups combined in the form of ethers, depends on this property (cf. p. 80). 

Chloro - pentammino - iridium Chloride, [Ir(NH3)sCl]Cl2, is formed by the action of ammonia on iridium trichloride, iridium tetrachloride, or the ehloro-double salts. It may also be prepared from chloro-pentammino-iridium sulphate by treating it with barium chloride. Prepared by the first method it separates in wine-coloured crystals, whilst by the second method it is yellow. The red colour of the first product is due to a small quantity of iridium trichloride, which separates with the chloro-ehloride and may be removed by heating the hot aqueous solution with hydrogen sulphide. It crystallises in 1 Jorgensen, J. prakt. Ghem., 1888, 34, 394 Palmaer, Ber., 1891, 24, 2090. 

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