Oxidizing agents arsenic acid

Arsenic is inert at room temperature, but ignites when heated, burning with a lavender flame to produce white clouds of the trioxide. It is oxidized to arsenic acid, HgAsO, by hot nitric acid and other powerful oxidizing agents. Arsenic combines with many other elements, both metallic and non-metallic. 

Cerium(IV) ions are strong oxidizing agents in acidic solution, oxidizing arsenious acid to arsenic acid according to the following equation ... 

Arsenates are oxidizing agents and are reduced by concentrated hydrochloric acid or sulfur dioxide. Treatment of a solution of orthoarsenate with silver nitrate in neutral solution results in the formation of a chocolate-brown precipitate of silver orthoarsenate, Ag AsO, which may be used as a test to distinguish arsenates from phosphates. With hydrofluoric acid, orthoarsenate solutions yield hexafluoroarsenates, eg, potassium hexafluoroarsenate [17029-22-0] (KAsFg)2 H2O. Arsenates of calcium or lead are used as insecticides sodium arsenate is used in printing inks and as a mordant. 

To illustrate case a, ii we may refer to the reduction of chlorate by arsenious acid induced by different 1-equivalent oxidizing reagents. The effect of the oxidizing agent is to form arsenic(IV). Chlorate will be reduced by arsenic(IV) which is a stronger reducing agent than arsenic(III). 

It is striking that reactions of arsenic(III) with 1-equivalent oxidizing agents take place fairly slowly, while reactions with 2-equivalent partners e.g. with iodine, are fast. To interpret this behaviour it was suggested by Waters that arsenious acid has the tautomeric forms... 

Oxidation Trivalent arsenic citric acid or EDTA Potassium permanganate depending on chelating agent, metal chelate is either strongly sorbed to soil or is highly mobile and can be flumbed usinj water or dilute acid solutions. Oxidizes trivalent arsenic to pentavalent... 

The best known exceptions to the general reluctance of bromine to accept a + 7 oxidation stale are perbroinic acid and the perbromate ion, which were unknown prior to 1968 (see Chapter 17). Their subsequent synthesis has made their nonexistence" somewhat less crucial as a topic of immediate concern to inorganic chemists, but bromine certainly continues the trend started by arsenic and selenium Thus the perbromate ion is a stronger oxidizing agent than either perchlorate or periodate. 

Arsenious oxide may be precipitated from acid solutions containing arsenic acid by treatment with reducing agents,5 for example, by passing sulphur dioxide under pressure into the agitated liquid. Precipitation may be assisted by concentration or cooling, or by addition of finely divided arsenious oxide to the well-stirred solution. 

The ugly name of the Skraup reaction appropriately applies to the worst witch s brew of all the heterocyclic syntheses. Some workers have added strange oxidizing agents such as arsenic acid, iron (III) salts, tin (IV) salts, nitrobenzenes of various substitution patterns, or iodine to make it go better . 

---