Precipitation by hydrogen sulfide

Iron Add 2 mL of hydrochloric acid and 0.1 mL of nitric acid to the residue from Substances Not Precipitated by Hydrogen Sulfide (below), cover with a watch glass, and digest on a steam bath for 20 min. Remove the watch glass, and evaporate to dryness. Dissolve the residue in 1 mL of hydrochloric acid, and dilute to 60 mL with water. Dilute 5 mL of this solution to 40 mL with water, add 2 mL of hydrochloric acid, and dilute to 50 mL with water. Add 40 mg of ammonium peroxydisulfate crystals and 10 mL of ammonium thiocyanate TS, and mix thoroughly. Any red color produced within 1 h shall not exceed that produced by 0.033 mg of iron in an equal volume of solution containing the reagents used in the test. 

Substances Not Precipitated by Hydrogen Sulfide Dissolve 5 g of sample in 200 mL of 1 100 sulfuric acid, heat to 70°, and pass hydrogen sulfide through the solution until the copper is completely precipitated. Dilute to 250 mL, mix thoroughly, allow the precipitate to settle, and filter. Evaporate 200 mL of the filtrate to dryness in a tared dish, ignite at 800° 25° for 15 min, cool, and weigh. 

Cysteine hydrochloride 567 Tin foil is added to a solution of cystine in hydrochloric acid, the metal at first dissolving without evolution of hydrogep. When gas evolution becomes prominent the mixture is diluted and the tin is precipitated by hydrogen sulfide. The filtrate therefrom is evaporated to dryness. 

Antimony trichloride can be prepared from stibnite, Sb2Ss, the chief ore of antimony. The solubility of this sulfide is intermediate between those of copper sulfide and zinc sulfide, so that it can be precipitated by hydrogen sulfide from 0.3M hydrochloric acid but is easily soluble in 12M hydrochloric acid. 

If arsenic is to be detected in the presence of large amounts of colored ions, it is best to carry out the test on the mixture of sulfides precipitated in acid solution. It must be noted, however, that when arsenic is present in the quinquevalent form, it is slowly and incompletely precipitated by hydrogen sulfide in the cold. The precipitation can be remarkably accelerated by the addition of small amounts of potassium iodide. 

Silver sulfide can also be used as a reduction nucleus, provided other metals precipitable by hydrogen sulfide and nitric acid are absent. 

Nickel sulfide, NiS, can be prepared by the fusion of nickel powder with molten sulfur or by precipitation usiag hydrogen sulfide treatment of a buffered solution of a nickel(II) salt. The behavior of nickel sulfides ia the pure state and ia mixtures with other sulfides is of iaterest ia the recovery of nickel from ores, ia the high temperature sulfide corrosion of nickel alloys, and ia the behavior of nickel-containing catalysts. 

Hydrochloric acid digestion takes place at elevated temperatures and produces a solution of the mixed chlorides of cesium, aluminum, and other alkah metals separated from the sUiceous residue by filtration. The impure cesium chloride can be purified as cesium chloride double salts such as cesium antimony chloride [14590-08-0] 4CsCl SbCl, cesium iodine chloride [15605 2-2], CS2CI2I, or cesium hexachlorocerate [19153 4-7] Cs2[CeClg] (26). Such salts are recrystaUized and the purified double salts decomposed to cesium chloride by hydrolysis, or precipitated with hydrogen sulfide. Alternatively, solvent extraction of cesium chloride direct from the hydrochloric acid leach Hquor can be used. 

Co-precipitation of Re S with platinum sulfide from cone, hydrochloric acid solutions of microamounts of technetium and rhenium is suitable for the separation of technetium from rhenium , since technetium is only slightly co-precipitat-ed under these conditions (Fig. 7). At concentrations of 9 M HCl and above, virtually no technetium is co-precipitated with platinum sulfide at 90 °C, whereas rhenium is removed quantitatively even up to 10 M HCl. The reduction of pertechnetate at high chloride concentration may be the reason for this different behavior, because complete co-precipitation of technetiiun from sulfuric acid solutions up to 12 M has been observed. However, the separation of weighable amounts of technetium from rhenium by precipitation with hydrogen sulfide in a medium of 9-10 M HCl is not quantitative, since several percent of technetiiun coprecipitate with rhenium and measurable amounts of rhenium remain in solu-tion . Multiple reprecipitation of Re S is therefore necessary. 

The higher sulfides of tellurium such as TeS2 and TeSs, are obtained from tellurite solutions by precipitation with hydrogen sulfide or sodium sulfide. Tellurium reacts with concentrated sulfuric acid to form red oxysulfide of the composition, TeSOs. With nitric acid, the metal is oxidized to dioxide, Te02. Oxidation of tellurium with chromic acid or potassium permanganate in nitric acid yields orthotelluric acid (HeTeOe). 

In another industrial process, flue dusts from smelting lead and zinc concentrates are boiled in acidified water. Thallium dissolves and is separated from insoluble residues by filtration. Dissolved thallium in solution then is precipitated with zinc. Thallium is extracted from the precipitate by treatment with dilute sulfuric acid which dissolves the metal. The solution may also contain zinc, cadmium, lead, copper, indium, and other impurities in trace amounts. These metals are precipitated with hydrogen sulfide. The pure thallium sulfate solution then is electrolyzed to yield thallium. 

The method is based upon the precipitation of a solution of a stannous salt by hydrogen sulfide. The most available stannous salt is the chloride, which may... 

The chrome yellow pigments [4344-37-2], C.I. Pigment Yellow 34 77600 and 77603, are pure lead chromate or mixed-phase pigments with the general formula Pb(Cr,S)04 [3.131] (refractive index 2.3-2.65, density ca. 6 g/cm3). Chrome yellow is insoluble in water. Solubility in acids and alkalis and discoloration by hydrogen sulfide and sulfur dioxide can be reduced to a minimum by precipitating inert metal oxides on the pigment particles. 

Zinc and Cadmium Sulfides and Sulfoselenides. The raw materials for the production of these sulfide phosphors are high-purity zinc and cadmium sulfides, which are precipitated from purified salt solutions by hydrogen sulfide or ammonium sulfide [5.291], [5.296], [5.307], [5.310], The concentration of contaminants such as Fe, Co, or Ni must be below 1 % of the activator concentration. The Zn, Cd S can be produced by mixing precipitated zinc sulfide and cadmium sulfide. However, coprecipitation from mixed zinc-cadmium salt solutions is preferred because of the better homogeneity. 

A colorless solution is obtained from which the tin is removed by precipitation with hydrogen sulfide. On addition of sodium carbonate solution, 3-Amino-4-propoxybenzoic acid 2-(diethylamino)ethyl ester separates as an oil. When treated with one equivalent of hydrochloric acid it forms a hydrochloride, which is readily soluble in water and crystallizes from a mixture of absolute alcohol and ethyl acetate in white prisms MP 182.0-183.3°C. 

Tin(IV) sulfide can be prepared by hydrogen sulfide precipitation of Sn(IV) from solution, to produce a microcrystalline material that is contaminated with oxide. Mosaic gold is a crystalline form of tin(IV) sulfide prepared by high-tempera-ture sublimation procedures. Mosaic gold is the reported product of heating mixtures of (1) tin and sulfur (2) tin, sulfur, and ammonium chloride (3) tin, sulfur, mercury, and ammonium chloride 9 (4) tin(II) oxide, sulfur, and ammonium chloride 9 (5) tin(II) chloride and sulfur 9 (6) tin(II) sulfide, tin(II) chloride, and sulfur.9... 

The d(—)-tartaric acid was recovered by decomposing the acid salt with excess ammonium hydroxide and removing the base by filtration. The filtrate was made barely acid with acetic acid and lead D-tartrate was precipitated with lead acetate solution. The filtered and washed lead D-tartrate was suspended in water and the lead removed by precipitation with hydrogen sulfide. The clear filtrate was evaporated to a small volume and allowed to crystallize in a desiccator. Recovery of 96.5% of d( — )-tartaric acid from the original acid salt was obtained after one recrystallization from water, it showed a specific rotation [< Pd of —14.2° (H20, l = 4, c = 4.05) and a melting point of 168-170° (corr.), which are the known values for pure d(—)-tartaric acid. 

Zinc salts, in the presence of sodium acetate, yield a white precipitate with hydrogen sulfide. This precipitate, which is insoluble in acetic acid, is dissolved by 2.7 N hydrochloric acid. A similar precipitate is produced by ammonium sulfide TS in neutral or alkaline solutions. Solutions of zinc salts yield with potassium ferrocyanide TS (10%) a white precipitate that is insoluble in 2.7 N hydrochloric acid. 

Chrome yellow is insoluble in water. Solubility in acids and alkalis and discoloration by hydrogen sulfide and sulfur dioxide can be reduced to a minimum by precipitating inert metal oxides on the pigment particles. 

Mercuric sulfide, HgS, is formed as a black precipitate when hydrogen sulfide is passed through a solution of a mercuric salt It can also be made by rubbing mercury and sulfur together in a mortar The black sulfide (w hich also occurs in nature as the mineral metacinna-barite) is converted by heat into the red form (cinnabar). Mercuric sulfide is the most insoluble of metallic sulfides. It is not dissolved even by boiling concentrated nitric acid, but it does dissolve in aqua regia, under the combined action of the nitric acid, which oxidizes the... 

Nickel is deposited quantitatively from ammoniacal solutions, incompletely from weakly acidic solutions, and not at all from strongly acidic ones. (A quantitative separation of copper from nickel requires that the acid concentration be kept high.) Among the important interferences in the determination of nickel are silver, copper, arsenic, and zinc, which can be removed by precipitation with hydrogen sulfide. Iron(II) and chromates are objectionable, but can be removed by precipitation of the hydrous oxides. 

Many substances catalyze the decomposition of organic compounds by sulfuric acid. Mercury, copper, and selenium, either combined or in the elemental state, are effective. Mercury(II), if present, must be precipitated with hydrogen sulfide prior to distillation to prevent retention of ammonia as a mercury(II) ammine complex. 

Tin is left in solution if molybdenum sulfide is precipitated in the presence of oxalic acid by hydrogen sulfide in a pressure bottle. In ores if outsitcrite jH present, it. may Is left with the insoluble residue hy dissolving the molybdenum with an add. 

For the analysis of rhenium, the sample is fused with sodium peroxide and rhenium precipitated from hydrochloric acid solution as Re2S7 by hydrogen sulfide. The precipitate is dissolved in aqueous sodium peroxide and from dilute sulfuric acid solution, rhenium is determined by electrodeposition.8 Chlorine is determined gravimetrically by fusion of the sample with a sodium carbonate/ sodium nitrate mixture (95 5) in a platinum crucible and then precipitating as silver chloride. 

Trithiocyclopentanone and trithiohexanone (trispiro- [j-trithiane-2,1 4,1// 6,l///-tri(cyclo-pentane) and -tri(cyclohexane)] )404 Gaseous hydrogen chloride, followed by hydrogen sulfide to saturation, is passed into a solution of cyclopentanone or cyclohexanone in five times the amount of anhydrous ethanol. A mass of crystals soon separates, which is filtered off and washed with dilute ethanol. When recrystallized from ethanol, trithiocyclopentanone melts at 99° when dissolved in chloroform and precipitated by ethanol, trithiocyclohexanone melts at 101-102°. 

Benzophenone anil (7 g) is dissolved in benzene (50 ml) in a hydrogenation vessel and treated with dry hydrogen chloride, which precipitates the yellow hydrochloride. The hydrogen chloride is then replaced by hydrogen sulfide, and the vessel is shaken for 6 days under the pressure from a Kipps apparatus. The resulting deep blue solution is filtered under carbon dioxide from the precipitated aniline hydrochloride and unchanged benzophenone anil hydrochloride, the benzene is evaporated in a stream of carbon dioxide, and the residue is fractionated. Thiobenzophenone (3 g) distils at 176-178°/18 mm as a deep blue oil, which solidifies on cooling but remelts in the warmth of a hand. 

Crystalline a, a-trehalose has been obtained as the dihydrate (m.p. 96-97°) from various natural sources (see Table II), and, in several cases, the identity of the sugar was confirmed by formation of the crystalline octaacetate (see Table III). Preparation of natural a,a-trehalose from vegetable and fungal sources involves extraction with ethanol, liberation from protein by the addition of lead acetate, removal of lead by precipitation with hydrogen sulfide, filtration, and decolorization with carbon. The sugar crystallizes readily from aqueous ethanol. An excellent method... 

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