Hydrogen sulphide analysis

As shown in Section 2.15, in a solution of 0.25M hydrochloric acid saturated with hydrogen sulphide (this is the solution employed for the precipitation of the sulphides of the Group II metals in qualitative analysis),... 

Some indication of risk of employee exposure to airborne chemicals can be gauged from an analysis of the level of exposure for comparison with known human dose/ response data such as those for carbon monoxide and hydrogen sulphide listed in... 

Aspartic Acid.—A portion of the aspartic acid, after separation from phenylalanine ester and after hydrolysis by baryta, may separate as barium salt this is the barium salt of racemic aspartic acid. The remainder is isolated, when the glutamic acid has been removed as hydrochloride, by boiling with lead hydroxide and treating with hydrogen sulphide to remove hydrochloric acid and lead respectively, and by crystallising from water. It maybe characterised by conversion into its copper salt, or by analysis, and is estimated by its weight. 

Under these conditions W. P. Bloxam obtained crystals of sulphur and of the pentasulphide, but no ruby-red crystals of the heptasulphide, and he obtained the enneasulphide by working according to J. Fritzsche s directions. P. Sabatier claims to have made the heptasulphide by digesting sulphur with the warm or cold mother liquid remaining after the separation of crystals of the pentasulphide. P. Sabatier s analysis corresponds with ammonium octomlpkide, (NH Sg. W. P. Bloxam made crystals of the hydrated salt, (NH4)2S7.fH20, by the simultaneous action of sulphur and hydrogen sulphide on aqua ammonia rather more cone, than that used in the preparation of the pentasulphide. 

The application of thiocyanogen in volumetric analysis is restricted by the necessity of using anhydrous solvents and dry vessels, to avoid hydrolysis. With a sufficient excess of sodium thiosulphate or hydrogen sulphide, respectively, thiocyanogen reacts quantitatively according to the equations ... 

Qualitative Analysis.—The minium is treated with dilute nitric acid effervescence indicates carbonates in the solution the lead is precipitated by means of hydrogen sulphide, the filtrate being tested for zinc, iron, aluminium, calcium and magnesium by the ordinary methods. The brown residue insoluble in nitric acid is heated further with nitric add in presence of either sugar solution or hydrogen peroxide until the lead dioxide is completely dissolved any insoluble residue then remaining may contain lead sulphate, barium sulphate or clay, which may be identified in the usual way. 

Free Mercury and Mercuric Nitrate.—In absence of lead compounds, free mercury Or -mercuric nitrate may be detected by shaking the vermilion with nitric acid diluted to twice its volume, filtering the solution and treating with hydrogen sulphide in presence of mercury or mercuric nitrate, a black precipitate is obtained. If, however, lead compounds are present, the precipitate should be examined by the ordinary methods of qualitative analysis to ascertain if it contains mercuric sulphide. 

Staszewski, R., Pompowski, T., Janak, J. Analysis of a mixture of carbon dioxide, hydrogen sulphide, carbonyl sulphide, carbon disulphide and sulphur dioxide by gas-liquid chromatography. Chem. Anal. 8, 897 (1963). — Chem. Abstr. 60, 15141 (1964). 

Katoh, T. Gas chromatographic analysis of hydrogen sulphide in air and waste gas. 

Vitenberg et al. [623] have described a gas chromatographic method for the determination of traces (down to l-10pg kg ) of sulphur compounds, such as hydrogen sulphide, mercaptans, sulphides and disulphides, in industrial waste waters (kraft paper mill effluents) by a combination of headspace analysis and microcoulometiy. This method increases the analytical sensitivity 102-103 times without any preliminary concentration of the sample. 

An alternative approach, adopted by Albery et al. [59-61], is to determine the mechanism giving rise to the sensor response and to use this information together with the measured data at short times to calculate the final response. This was used for an electrochemical sensor system incorporating cytochrome oxidase where the steady-state responses of the measurement system were insufficiently fast for useful measurement of respiratory inhibitors such as cyanide, hydrogen sulphide, etc. By using mechanistic information, it was possible to successfully calculate the concentration in a test sample by real-time analysis of the sensor signals at short times after exposure to the test sample. The analysis could cope with the gradual loss of enzyme activity commonly found in these biosensor devices. 

Wet Tests.—In qualitative analysis by Wet Methods, it is usual to precipitate cobalt, along with any nickel, zinc, and manganese that may be present, by passage of hydrogen sulphide through an ammoniacal... 

When dilute reagents are used—for example, nickel sulphate and ammonium sulphide in dilute aqueous solution—probably the a compound is first formed, and then, when the solubility of this substance is exceeded, a precipitate separates out which subsequently more or less completely polymerises to the [3 and y forms. This suffices to explain the well-known fact in qualitative analysis that whilst nickel sulphide cannot be precipitated in acid solution by hydrogen sulphide, yet when once precipitated in alkaline solution it is very difficult to dissolve again completely in dilute mineral acid.11... 

Properties.—Thiophosphoryl chloride is a transparent colourless liquid which fumes in the air and smells of hydrogen sulphide. The formula has been established by analysis and vapour density determination. The density of the liquid is 1-66820 at 0° C. and 1-45.599 at the normal boiling-point, 125-12° C.8 The coefficient of expansion between these temperatures is given by8... 

Precipitation of sulphides Hydrogen sulphide gas is a frequently used reagent in qualitative inorganic analysis. When hydrogen sulphide gas is passed into a solution, metal sulphides are precipitated. For this precipitation the rule mentioned above can be applied precipitation may take place only if the product of concentrations of metal ions and sulphide ions (taken at proper powers) exceed the value of the solubility product. While the concentration of metal ions usually does fall into the range of 1-10 3 mol 1, the concentration of sulphide ion may vary considerably, and can easily be selected by the adjustment of the pH of the solution to a suitable value. 

Hydrogen sulphide H2S Hydrogen sulphide gas or its saturated solution is used as a precipitant in qualitative inorganic analysis. If oxidizing ions, like Cr202-, MnO, Fe3+, AsO - or substances like HN03 or Cl2 are present, it undergoes oxidation, when elementary S is formed ... 

The following interfere with the test strong reducing agents (hydrogen sulphide, dithionites, sulphites and selenites) V, U, Te, Hg, Bi, Au, Pd, Se, Te, Sb, Mo, W, Co and Ni. The reaction is not selective, but is fairly sensitive it can be used in the analysis of the Group IIB precipitate. Since iron(II) ions have no influence on the test, it may be applied to the tin solution which has been reduced with iron wire. 

To avoid the production of sulphur by the reduction of potassium permanganate by hydrogen sulphide in systematic qualitative analysis, the solution may be reduced with formaldehyde solution, or the solid substance may be boiled with concentrated hydrochloric acid. The use of sulphur dioxide is not recommended (see footnote in connection with Chromates, Section IV.33, reaction 5). 

If borate is found to be present, transfer the centrifugate from Group II to a small crucible, heat to expel hydrogen sulphide (do not evaporate to dryness), and allow to cool. Add 2-3 drops concentrated hydrochloric acid and 5-6 drops methanol, and heat on a water bath until the solution is almost evaporated to dryness. Repeat the addition of hydrochloric acid and methanol, and evaporate to dryness on the water bath. If borate is the only interfering ion, dissolve the residue in 2 ml of 2m hydrochloric acid, and continue the analysis for cations. The borate is volatilized as methyl borate (poisonous). 

Qualitative work was accomplished in part by Fresenius s analysis scheme using hydrogen sulphide, or sulphuretted hydrogen, as it was then called. In the annual report for 1906, the purchase of a new Kipp s apparatus was announced ... 

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