Ammonium sulphide group

It is convenient to include under Aromatic Amines the preparation of m-nitroaniline as an example of the selective reduction of one group in a polynitro compound. When wt-dinitrobenzene is allowed to react with sodium polysulphide (or ammonium sulphide) solution, only one of the nitro groups is reduced and m-nitroanUine results. Some sulphur separates, but the main reaction is represented by ... 

Groups Dodecacarbonyidi vanadium (Ammonium sulphide) Triethylphosphine... 

In routine analysis arsenic is precipitated from acid solution as sulphide and with antimony, molybdenum and tin is separated from the copper group by dissolution in yellow ammonium sulphide. The sulphides are reprecipitated from this solution by acidifying, and on treatment with concentrated hydrochloric acid all the sulphides, except arsenic, redissolve. The latter dissolves in aqua regia and arsenic may be identified in the solution by applying one of the tests described in the sequel.1... 

On reduction, acid reducing agents attack the a- nitro group preferentially, while sodium and ammonium sulphides reduce the p- nitro group. 

The group reagents used for the classification of most common cations are hydrochloric acid, hydrogen sulphide, ammonium sulphide, and ammonium carbonate. Classification is based on whether a cation reacts with these reagents by the formation of precipitates or not. It can therefore be said that classification of the most common cations is based on the differences of solubilities of their chlorides, sulphides, and carbonates. 

Group III Cations of this group do not react either with dilute hydrochloric acid, or with hydrogen sulphide in dilute mineral acid medium. However they form precipitates with ammonium sulphide in neutral or ammoniacal medium. Cations of this group are cobalt(II), nickel(II), iron(II), iron(III), chromium(III), aluminium, zinc, and manganese(II). 

AU the sulphides of the arsenic sub-group dissolve in (colourless) ammonium sulphide except tin(II) sulphide to dissolve the latter, ammonium polysulphide is needed, which acts partly as an oxidizing agent, thiostannate ions being formed ... 

Group reagent hydrogen sulphide (gas or saturated aqueous solution) in the presence of ammonia and ammonium chloride, or ammonium sulphide solution. 

Group reagent there is no common reagent for the cations of this group. Group reaction cations of the fifth group do not react with hydrochloric acid, hydrogen sulphide, ammonium sulphide or (in the presence of ammonium salts) with ammonium carbonate. Special reactions or flame tests can be used for their identification. 

The wash liquid for the Group IIIB precipitate may consist of 1 per cent NH4C1 to which 1 per cent by volume of ammonium sulphide solution is added. Oxidation of the moist sulphides to the soluble sulphates is thus considerably reduced. 

The filtrate must be acidified immediately and concentrated to remove H2S. Ammonium sulphide solution on exposure to air slowly oxidizes to ammonium sulphate and would then precipitate any barium or strontium present as BaS04 or SrS04. Another reason for the immediate acidification of the filtrate from Group IIIB is to prevent the absorption of C02 from the air with the attendant formation of carbonate ions the latter would also precipitate the ions of Group IV. 

Table V.25 Separation of Group IIIB cations with the hydrochloric acid-potassium chlorate-hydrogen peroxide method The ppt. may contain CoS, NiS, MnS, and ZnS. Wash well with 1 per cent NH4C1 solution to which 1 per cent by volume of yellow ammonium sulphide solution has been added reject the washings. Transfer the ppt. to a porcelain basin, add 5 ml water and 5 ml concentrated HC1 and stir for 2-3 minutes. If a black residue is obtained, the presence of NiS and CoS is indicated if complete dissolution takes place, only small amounts of Ni and Co are likely to be present. Evaporate the mixture to 2-3 ml in the FUME CUPBOARD, add 4 ml concentrated HN03 (1) and concentrate to 2-3 ml. If the solution is not clear, dilute with 8-10 ml water, filter off the sulphur and return the filtrate to the porcelain basin in the fume cupboard. Boil down to 1-2 ml, taking great care not to evaporate to dryness. Add 5 ml concentrated HN03 and evaporate again to 1-2 ml (2).

Any thallium not precipitated in Group I as T1C1, will ultimately be found in the precipitate of Group IIIB. It is best to dissolve the Group IIIB precipitate in dilute nitric acid, boil to expel H2S, add a few drops of sulphurous acid and boil to expel excess S02. The resulting solution is then poured into excess sodium carbonate solution when the carbonates of cobalt, nickel, manganese, and zinc are precipitated. The thallium remains in solution as thallium(I) carbonate and can be precipitated as thallium(I) sulphide, T12S, by the addition of ammonium sulphide solution. 

Separation. Selenium and tellurium are precipitated in Group II as the yellow Se-S mixture and brown Te-S mixture respectively. Both dissolve in ammonium sulphide solution and are precipitated with As2S3 upon the addition of concentrated HC1. They may be identified by the H2S03 tests. 

Some teachers may prefer not to carry out a complete separation of cations, but to hand out separate unknown mixtures containing cations of one analytical group only. In this case precipitation is made of the particular group reagent (hydrochloric acid, hydrogen sulphide, ammonia, ammonium sulphide or ammonium carbonate) and the precipitate is examined by Group Separation Tables V. 12 to V. 19 as well as V.23 to V.28 for each group respectively. 

Wet Tests.— When hydrogen sulphide is passed through an acidified solution containing molybdenum, the trisulphide is thrown dowm. The precipitate dissolves in ammonium sulphide, and it is therefore in ordinary analysis separated with the Group IIb metals, namely, arsenic, antimony, tin, gold, and platinum. The last four metals may be precipitated by addition of metallic zinc, the arsenic expelled by evaporation, and, after taking to dryness with nitric acid, the molybdenum may be extracted from the residue with ammonia. The trisulphide may be reprecipitated directly by the addition of nitric acid to the solution in ammonium sulphide. A soluble sulphide added to a solution of ammonium molybdate gives a blue colour. 

The chloride is very soluble in acetone, soluble in hot alcohol or ether, only slightly soluble in water. W hen treated with bromine in potassium bromide for tw o hours on a shaking machine, and then extracted with ether, o-bromonitrobeiizene, M.pt. 41° to 42° C., is obtained, which shows the mercury to be in the ortho position to the nitro group. No mercuric sulphide is obtained when the chloride is acted upon by ammonium sulphide, but when boiled with hydrochloric acid nitrobenzene results. During the direct mercuration of nitrobenzene, mercury o-o dinitrodi henyl, M.pt. 206° C., is also formed. ... 

Acetoxymercuri-m-dimethylamiiiophenyl acetate is prepared as above, using m-dimethylaminophenyl acetate. Yield 78 per cent. It forms colourless crj stals, M.pt. 110° C. (corr.), readily soluble in hot alcohol. The cold alcoholic solution with ammonium sulphide gives a yellow precipitate which blackens in a few minutes. When the substance is warmed for a few minutes with dilute sodium hydroxide, cooled and neutralised with acetic acid, ammonium sulphide immedi-ately gives mercuric sulphide. This is no doubt due to the hydrolysis of the acetyl group by alkali and the formation of the less stable mercury derivative of m-dimethylaminophenol. The dry acetate blackens when kept for several months,... 

The anhydride of a-hydroxymereuri-j8-hydroxy-j8-phenylpropionic acid in alkaline solutions only yields mercuric sulphide on long standing with ammonium sulphide but if the j3-hydroxy group be replaced by methoxy, the decomposition takes place immeiately. 

Lead dimethyl dichloride,Pb(CH3)2Cl2.— When lead tetra-alkyls are treated with halogen at —20° C. two alkyl groups are removed. The dichloride is practically insoluble in most organic solvents, and has a strong acid reaction in warm water. The oxide dissolves in weak acids and in caustic alkalies. The sulphide is soluble in hydrochloric acid or ammonium sulphide, insoluble in acetic acid, but the chromate is soluble in the latter. The dibromide has similar properties to the dichloride, and a di-iodide has also been prepared. 

Gevekoht [50] obtained indigotin by action of ammonium sulphide on ortho-nitroacetophenoiie, in which the methyl group is brominated. 

The complete reduction of nitto-compounds containing several nitre-groups is conducted in the same way as for mononitro-compounds. If it is desired to reduce but one or two of several nitro-groups, it cannot be done by adding just the calculated amount of the reducing agent for cases of this kind, special methods are necessary. For this purpose, hydrogen sulphide in the presence of ammonia or ammonium sulphide is often used for the reduction ... 

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