Alkali Iodates

Reaction (11.4) is really a disproportionation reaction of the halate(I) anion 3XO 2X -E XO. ) Reaction (11.3) is favoured by the use of dilute alkali and low temperature, since the halate(I) anions, XO are thermally unstable and readily disproportionate (i.e. reaction (11.4)). The stability of the halate(I) anion, XO , decreases from chlorine to iodine and the iodate(I) ion disproportionates very rapidly even at room temperature. 

In addition to the stable I2O5 and moderately stable I4O9 and I2O4, several short-lived radicals have been detected and characterized during y-radiolysis and flash photolysis of iodates in aqueous alkali ... 

The modes of thermal decomposition of the halates and their complex oxidation-reduction chemistry reflect the interplay of both thermodynamic and kinetic factors. On the one hand, thermodynamically feasible reactions may be sluggish, whilst, on the other, traces of catalyst may radically alter the course of the reaction. In general, for a given cation, thermal stability decreases in the sequence iodate > chlorate > bromate, but the mode and ease of decomposition can be substantially modified. For example, alkali metal chlorates decompose by disproportionation when fused ... 

In general the iodonium bases are formed from iodoso- and iodoxy-compounds in the presence of alkali, preferably silver oxide the two organic iodine compounds combine with elimination of iodate. 

Intimate mixtures of chlorates, bromates or iodates of barium, cadmium, calcium, magnesium, potassium, sodium or zinc, with finely divided aluminium, arsenic, copper carbon, phosphorus, sulfur hydrides of alkali- and alkaline earth-metals sulfides of antimony, arsenic, copper or tin metal cyanides, thiocyanates or impure manganese dioxide may react violently or explosively, either spontaneously (especially in presence of moisture) or on initiation by heat, friction, impact, sparks or addition of sulfuric acid [1], Mixtures of sodium or potassium chlorate with sulfur or phosphorus are rated as being exceptionally dangerous on frictional initiation. 

Results obtained from the alkali iodides on the isomer shift, the NMR chemical shift and its pressure dependence, and dynamic quadrupole coupling are compared. These results are discussed in terms of shielding by the 5p electrons and of Lbwdins technique of symmetrical orthogonalization which takes into account the distortion of the free ion functions by overlap. The recoilless fractions for all the alkali iodides are approximately constant at 80°K. Recent results include hybridization effects inferred from the isomer shifts of the iodates and the periodates, magnetic and electric quadrupole hyperfine splittings, and results obtained from molecular iodine and other iodine compounds. The properties of the 57.6-k.e.v. transition of 1 and the 27.7-k.e.v. transition of 1 are compared. 

For the iodate method, chlorine in concentrations below 1 mass % does not interfere. The isoprene rubber method can tolerate somewhat higher levels. Nitrogen when present above 0.1 mass % may interfere with the iodate method, the extent depending on the types of nitrogen compounds as well as the combustion conditions. It does not interfere in the infrared method. The alkali and alkaline earth metals, zinc, potassium, and lead do not interfere with either method. 

Salts of very powerful oxidizing acids (eg chromic or permanganic) are unknown, and are unlikely to exist. Hydrazonium iodate may exist in solution at low temp (Ref 27a). Alkali metals, amides and hydrides react with hydrazine to give the corresponding alkali hydrazide. Sodium hydrazide explodes violently in the presence of 02 or when heated above 100°C—a typical behavior of the alkali hydrazides. For other reactions, see Ref 24 Explosive and Combustion Properties... 

Analytical. Hydrazine content in aqueous solutions is determined by reacting with picryl chloride to form the yellow hexanitro hydrazobenzene, which, with alkali forms red or violet salts that can be measured colorimetrically (Ref 3). More concentrated solution of hydrazine can be titrated with either standard iodine or iodate solutions according to the following equations (Ref 4) ... 

Varhelyi Kekedy studied the thermal decomposition of iodates periodates by thermo-gravimetric methods (Ref 2). They found that there is no similarity in the decomposition of univalent iodates, but most divalent iodates -decompose similarly since their decomp temps are similar. The thermal stability (ie their resistance to decomposition into iodates) increases as follows of the alkali periodates Lithermal stability of alkaline earth periodates increases in the order Ca[Pg.381]

The violence of the explosion is feebler with iodates than it is with chlorates or bromates. The chlorates transform lead oxide to the dioxide manganese oxide in fused alkalies to manganates etc. Ammonium iodate explodes when heated alone. Chloric, bromic, and iodic acids with their salts are energetic oxidizing agents. 

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