Alkali sulfides

The solubility in alkali sulfide solutions stems from the presence of disulfide groups —S—S— in ortho position to the terminal amino groups. These disulfide groups are reduced to the mercapto groups —SH, which are soluble in alkaU. 

Nitro-filter cloths are composed of cellulose nitrate, which is an ester of cellulose. Any chemical compound that will saponify the ester will destroy the cloth. Caustic soda or potash in strengths of 2% at 70° C or over alkali sulfides, polysulfides and sulfohydrates or mixtures of ethyl alcohol and ether, ethyl, amyl and butyl acetates, pyridine, ferrous sulfates, and other reducing agents are detrimental to the cloth. 

Selective reduction (e.g., partial reduction of one of two nitro groups) is carried out with an alkali sulfide, such as sodium hydrogen sulfide NaHS ( sodium sulfhy-drate ) or sodium sulfide Na2S, in an aqueous or alcoholic solution. Azo groups are not affected by this method. The reaction converts sodium hydrogen sulfide or sodium sulfide mainly to sodium thiosulfate. 

Similar reducing effects are obtained from alkali sulfides, hydrosulfides and polysulfides [241]. A peculiar reaction believed to be due to sodium polysulfide formed in situ by refluxing sulfur in aqueous-ethanolic sodium hydroxide is a conversion of p-nitrotoluene to p-aminobenzaldehyde [242]. Oxidation of the methyl group by the polysulfide generates hydrogen sulfide which then reduces the nitro group to the amino group. 

The main field of applications of hydrogen and alkali sulfides is reduction of nitrogen functions in nitro compounds [236, 240], nitroso compounds... 

Sulfurized Vat Dyes. These dyes occupy an intermediate position between the true vat colors and sulfur dyes because, like vat dyes, they are dyed preferentially from a sodium dithionite—caustic soda bath. However, some dyes of this class can also be dyed from an alkali sulfide bath or a combination of the two, depending on the dyeing method used and the nature of the substrate to be dyed. This has led to some confusion because Cl Vat Blue 42 and 43 are listed in the constitution section of the Colour Index under sulfur dyes. Although inferior to true vat dyes in fastness properties, they offer the advantage of better fastness, especially to chlorine, than conventional sulfur dyes. 

Direct fusion of the elements yields a number of arsenic sulfides, including AsuS3, AS4S4, As2S3, and As2S , the last two being obtained also by precipitation from arsenic (III) and arsenic (V) solutions, respectively. The disulfide dissolves in alkali sulfide solutions to form diio-arsenites ... 

This however is not the whole story, for resinous products, oxalic acid, and ammonia are also formed. If the reaction with caustic alkali is carried out in the presence of thiophenol, some glycerin is formed and the thiophenol is oxidized to diphenyl sulfide. Alkali sulfides, K2S, KHS, and CaS, also yield glycerin. 

When hydrogen sulfide reacts, with mercuric chloride in neutral or acid solution, or when mercury and sulfur are ground together, black mercuric sulfide is formed. Under certain conditions, this material can be converted into the red modification by the continued action of soluble alkali sulfides. The reaction of mercuric chloride and sodium thiosulfate gives the red form if the ratio of the concentrations is higher than 1 4d The red sulfide is also produced when the substance Hg(SH)NCS is boiled with concentrated ammonium thiocyanate solution or when hydrogen sulfide is conducted into a warm mercuric salt solution in the presence of acetic acid and an excess of ammonium thiocyanate, or thiourea.2,3... 

The different states of polarization of a film of a given substance deposited upon different carriers cause these films to react very differently. Manganous sulfide, for example, dissolves readily in dilute acetic acid, but, according to Feigl (12), MnS is not soluble when precipitated on HgS. This interaction between the surface film of MnS and the carrier HgS is a mutual one. HgS is readily soluble in alkali sulfides. However, HgS precipitated on MnS loses some of its solubility in alkali sulfides. 

Cadmium pigments have been manufactured by both a direct calcination process and a precipitation-calcination process. In the first instance, a mixture of cadmium carbonate and sulfur (and zinc oxide and selenium if the hue to be produced requires their addition) is calcined at 520-600°C for 1-2 h. This direct calcination process is complicated by the volatility of cadmium oxide and selenium, both of which are toxic and require special handling. In the precipitation process, an alkali sulfide solution is added to a solution of cadmium and (in the case of green-shade yellows) zinc salts or to a solution of cadmium and (in the case of deep oranges, reds, and maroon) selenium metal to precipitate the appropriate compound. The precipitate is washed, dried, and calcined at 600-700°C in an inert or reducing atmosphere to convert the precipitated cubic structure to a more stable wurtzite crystal. The calcination conditions control particle size, which ranges from 0.2 to 1.0pm. 

Mercury-cadmium pigments were developed in the early 1950s as a more cost-effective alternative to cadmium sulfoselenides. Mercury replaces part of the cadmium in the cadmium sulfide compound and eliminates the need for selenium. The resulting pigments range from deep orange to a maroon and offer a cleaner, brighter chroma than their cadmium counterparts. Manufacture is the same as for cadmium sulfides, except that mercury salts are added to the cadmium solution that is reacted with the alkali sulfide solution to cause precipitation. 

Nitrogen in organosilicon compounds can be determined by the standard Kjeldahl method. Both silicon and nitrogen can be determined on the same sample by digesting it in concentrated sulfuric acid to which a drop of mercury has been added 18 the silica is filtered from the diluted acid, and ammonia is distilled from the filtrate after alkali sulfide and caustic solution have been added. The distilled ammonia is absorbed in standard acid, and the excess of acid is titrated in the usual manner. 

Only the alkalis and alkaline earths form sulfides that appear to be mainly ionic. They are the only sulfides that dissolve in water and they crystallize in simple ionic lattices, for example, an anti-fluorite lattice for the alkali sulfides and a rock salt lattice for the alkaline earth sulfides. Essentially only SH" ions are present in aqueous solution, owing to the low second dissociation constant of H2S. Although S2" is present in concentrated alkali solutions, it cannot be detected below 8 M NaOH owing to the reaction... 

Although sulfide species are commonly made from sulfur, alkali sulfides, or polysulfides, a useful procedure for converting oxoanions or alkoxides to sulfides is by use of trimethylsilyl sulfide, for example,... 

Brown hydrous M0S3, obtained on passing H2S into slightly acidified solutions of molybdates, dissolves on digestion with alkali sulfide solution to give brown-red thiomolybdates. 

Alkali Sulfide Solution, tion (iron, copper, tin, etc.). 

Two types of by- tfoduots appear durmg the preparation of thietane, windpally when the method employed is the cydlzation of a dihalo derivative with an alkali sulfide. 

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