Hydrogen sulfide precipitations

At least three pesticide plants use priority pollutant metals separation systems in the United States [7]. One plant uses hydrogen sulfide precipitation to remove copper from its pesticide wastewater. The operating system consists of an agitated precipitator to which the H2S is added, a soak vessel to which sulfur dioxide is added, a neutralization step using ammonia, and a gravity separation and centrifuging process. Copper is removed from an influent level of 4500 mg/L to 2.2 mg/L. 

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 precipitate was again dissolved in hydrochloric add. Now a copper foil was introduced. A precipitate was obtained even now, but small and almost invisible - small, but the carrier of the whole activity. This precipitate was again dissolved in hydrochloric acid and something unknown in the solution was precipitated by addition of stannous chloride SnClj. When filtered off, it was shown that its radioactivity was 3500 times greater than that of pure uranium. A further purification was made by hydrogen sulfide precipitation, dissolution and finally electrolytic precipitation. 

Carbonate is measured by evolution of carbon dioxide on treating the sample with sulfuric acid. The gas train should iaclude a silver acetate absorber to remove hydrogen sulfide, a magnesium perchlorate drying unit, and a CO2-absorption bulb. Sulfide is determined by distilling hydrogen sulfide from an acidified slurry of the sample iato an ammoniacal cadmium chloride solution, and titrating the precipitated cadmium sulfide iodimetrically. 

The precipitated acetyHde must be decomposed with hydrochloric acid after the titration as a safety measure. Concentrated solutions of silver nitrate or silver perchlorate form soluble complexes of silver acetyHde (89). Ammonia and hydrogen sulfide interfere with the silver nitrate method which is less... 

The removal of copper from the pregnant nickel solution in the Sherritt-Gordon process is an example of purification by precipitation of a fairly insoluble compound. First, in the copper boil step, ammonia is driven off by heating the solution, and some copper sulfide precipitates. The residual copper is removed by a dding hydrogen sulfide for the chemical precipitation of mote copper sulfide. 

In the acid-leaching process, the oxide ore is leached with sulfuric acid at elevated temperature and pressure, which causes nickel, but not iron, to enter into solution. The leach solution is purified, foHowed by reaction with hydrogen sulfide and subsequent precipitation of nickel and cobalt sulfides. 

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. 

The iodate is a poison potassium iodide, however, is used in foodstuffs. Thus the iodate must be completely removed frequently by a final reduction with carbon. After re-solution in water, further purification is carried out before recrystallization. Iron, barium, carbonate, and hydrogen sulfide are used to effect precipitation of sulfates and heavy metals. 

Silver Sulfide. Silver sulfide, Ag2S, forms as a finely divided black precipitate when solutions or suspensions of most silver salts are treated with an alkaline sulfide solution or hydrogen sulfide. Silver sulfide has a dimorphic crystal stmcture. Transition from the rhombic (acanthite) to the cubic (argentite) form occurs at 175°C. Both crystal stmctures are found in nature. 

Strontium carbonate also precipitates from strontium sulfide solution with carbon dioxide. Hydrogen sulfide is generated as a by-product of this reaction and reacts with sodium hydroxide to produce sodium hydrosulfide, which is sold as by-product. The abiUty of the black ash process to produce a product exceeding 95% strontium carbonate, from ores containing <85% strontium sulfate, has led to its predorninance. 

Hydrogen sulfide causes the precipitation of sulfides from many heavy-metal salts. The classical quaUtative analysis scheme depends on precipitation of the sulfides of Hg, Pb, Bi, Cu, Cd, As, Sb, and Sn under acid conditions and the sulfides of Co, Ni, Mn, Zn, and Fe under ammoniacal conditions. 

In metallurgy, hydrogen sulfide is used to precipitate copper sulfide from nickel—copper-containing ore leach solutions in Alberta, Canada, or to precipitate nickel and cobalt sulfides from sulfuric acid leaching oflaterite ores in Moa Bay, Cuba (120) (see Metallurgy, extractive metallurgy). 

Both iron and aluminum are particulady troublesome because of their abiUty to act as coagulants. Also, their soluble and insoluble hydroxide forms can each cause precipitation of some water treatment chemicals, such as orthophosphate. Airborne contaminants usually consist of clay and dirt particles but can include gases such as hydrogen sulfide, which forms insoluble precipitates with many metal ions. Process leaks introduce a variety of contaminants that accelerate deposition and corrosion. 

Arsenic pentasulfide (arsenic(V) sulfide), As S q, is stable in air up to 95°C, but at higher temperatures begins to dissociate into arsenous sulfide and sulfur. It is prepared by the fusion of arsenic with sulfur foUowed by extraction with ammonia and reprecipitation at low temperatures by addition of hydrochloric acid. Arsenic pentasulfide is precipitated at low temperatures from strongly acidic arsenate solutions by a rapid stream of hydrogen sulfide. It is hydrolyzed by boiling with water, yielding arsenous acid and sulfur. Salts derived from a number of thioarsenic acids are formed from arsenic pentasulfide and alkaH metal sulfides. 

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. 

In a copper or iron kettle of 4-I. capacity is placed a solution of 200 g. of d-tartaric acid and 700 g. of sodium hydroxide in 1400 cc. of water. A 12-I. flask through which cold water is run is placed in the mouth of the kettle in order to prevent loss of water vapor, and the mixture is boiled gently over an open flame for four hours. The solution is now transferred to a 12-I. flask or crock and partially neutralized with 1400 cc. of commercial hydrochloric acid (density 1.19). To the still alkaline solution is now added just enough sodium sulfide to precipitate all the iron or copper which has been dissolved from the kettle (Note i). The filtered solution is then just acidified with hydrochloric acid, boiled to expel all hydrogen sulfide, and made very faintly alkaline to phenolphthalein with sodium hydroxide solution. To the hot solution is then added a concentrated solution of 300 g. of anhydrous calcium chloride which causes an immediate precipitation of calcium tff-tartrate and mesotartrate. 

B. Aminolhymol.—The crude, wet nitrosothymol so obtained is worked up with a mixture of 900 cc. of 28 per cent ammonia water (sp. g. 0.90) and 1600 cc. of water the brown solution is filtered free of a little resinous matter, and hydrogen sulfide is passed into it. The brown color disappears and a white precipitate of aminothymol forms. The passage of hydrogen sulfide is continued for thirty minutes longer (Note 3), when the base is filtered and washed well with cold water, contact with air being avoided as far as possible (Note 4). 

The resulting -aminocaproic acid hydrochloride is treated in a manner similar to that used in the preparation of df-alanine (Org. Syn. Coll. Vol. i, 20). The hydrochloride is dissolved in r 1. of water in a 1.5-I. beaker and treated successively with 50 g. of powdered litharge, 25 g. of powdered litharge, 5 g. of freshly precipitated lead hydroxide, 25 g. of powdered silver oxide (Note 2), and finally hydrogen sulfide. During this procedure, the original volume is maintained by the addition of small amounts of water. 

The cleavage of the intermediate osmate ester has presented problems in the past, and a variety of procedures have been developed, including the use of mannitol and strong aqueous base, refluxing aqueous alcoholic sodium bisulfite,formaldehyde and ascorbic acid. A much milder method involves simply bubbling hydrogen sulfide into a solution of the osmate ester osmium dioxide is precipitated rapidly, and the desired organic... 

Extension of these studies to medium rings produced interesting results (73). The mercuric acetate oxidation of 1-methyl-1-azacyclooctane (64), when worked up in the usual manner, gave no distillable material. When an equivalent amount of hydrochloric acid was added to the solution which had been saturated with hydrogen sulfide to precipitate the excess mercuric acetate and filtered, evaporation of the solution to dryness gave a solid which was subsequently identified as 2,4,6-tris(6 -methylaminohexyl)-trithiane trihydrochloride (65). Two plausible routes to the observed... 

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