Thiosulfates. Thiosulfates are readily obtained by boiling solutions of sulfites with sulfur. The free acid is unstable at ordinary temperatures. The alkali thiosulfates are manufactured for use in photography where they are used to dissolve unreacted silver bromide from emulsion by formation of the complexes [Ag(S2O3)]-and [Ag(S2O3)2]3-; the thiosulfate ion also forms complexes with other metal ions.
The thiosulfate ion has the structure S—SO3 2-
Dithionates. The reduction of sulfites in aqueous solutions containing an excess of SO2, by zinc dust, gives ZnS204. The Zn2+ and Na+ salts are commonly used as powerful and rapid reducing agents in alkaline solution:
In the presence of 2-anthraquinonesulfonate as catalyst aqueous Na2S2O4 efficiently removes oxygen from Inert gases. The ion has the structure O2S—SO 22-with a long weak S—S bond.
Polythionates. These anions have the general formula [O3SSnSO3]2-.The corresponding acids are not stable, decomposing rapidly into S, SO2 and sometimes SO42- The well-established polythionate anions are those with n= 1—4. They are named according to the total number of sulfur atoms and are thus called: trithionate S3062-, tetrathionate S4062-, and so on. There is evidence for anions having chains with up to 20 sulfur atoms.
Tetrathionates are obtained by treatment of thiosulfates with iodine in the reaction used in the volumetric determination of iodine:
Peroxodisulfates. The NH4+ or Na+ salts are obtained by electrolysis of the corresponding sulfates at low temperatures and high current densities. The S2O82- ion has the structure O3S-O-O-SO3, with approximately tetrahedral angles about each S atom.
The ion is one of the most powerful and useful of oxidizing agents:
However, the reactions are complicated mechanistically. Oxidations by S2O82-are slow and are usually catalyzed by addition of Ag+ which is converted to Ag2+, the actual oxidant.
Study Questions
A
1.What are the two principal forms in which sulfur occurs in nature?
2. Ordinary solid sulfur consists of what species? Summarize briefly what is observed when sulfur is heated from below its melting point to above its boiling point and explain the reasons for these changes.
Thiosulfates. Thiosulfates are readily obtained by boiling solutions of sulfites with sulfur. The free acid is unstable at ordinary temperatures. The alkali thiosulfates are manufactured for use in photography where they are used to dissolve unreacted silver bromide from emulsion by formation of the complexes [Ag(S2O3)]-and [Ag(S2O3)2]3-; the thiosulfate ion also forms complexes with other metal ions.
The thiosulfate ion has the structure S—SO3 2-
Dithionates. The reduction of sulfites in aqueous solutions containing an excess of SO2, by zinc dust, gives ZnS204. The Zn2+ and Na+ salts are commonly used as powerful and rapid reducing agents in alkaline solution:
In the presence of 2-anthraquinonesulfonate as catalyst aqueous Na2S2O4 efficiently removes oxygen from Inert gases. The ion has the structure O2S—SO 22-with a long weak S—S bond.
Polythionates. These anions have the general formula [O3SSnSO3]2-.The corresponding acids are not stable, decomposing rapidly into S, SO2 and sometimes SO42- The well-established polythionate anions are those with n= 1—4. They are named according to the total number of sulfur atoms and are thus called: trithionate S3062-, tetrathionate S4062-, and so on. There is evidence for anions having chains with up to 20 sulfur atoms.
Tetrathionates are obtained by treatment of thiosulfates with iodine in the reaction used in the volumetric determination of iodine:
Peroxodisulfates. The NH4+ or Na+ salts are obtained by electrolysis of the corresponding sulfates at low temperatures and high current densities. The S2O82- ion has the structure O3S-O-O-SO3, with approximately tetrahedral angles about each S atom.
The ion is one of the most powerful and useful of oxidizing agents:
However, the reactions are complicated mechanistically. Oxidations by S2O82-are slow and are usually catalyzed by addition of Ag+ which is converted to Ag2+, the actual oxidant.
Study Questions
A
1.What are the two principal forms in which sulfur occurs in nature?
2. Ordinary solid sulfur consists of what species? Summarize briefly what is observed when sulfur is heated from below its melting point to above its boiling point and explain the reasons for these changes.
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