Hydriodic acid stabilization

Hydrazine dihydrochloride, 92 Hydrazine residues, recovery of, 92 Hydrazine sulfate, 90, 92 Hydrazoic acid, 77, 78 Hydriodic acid, 157, 159 by action of iodine on hydrogen sulfide, 157 constant boiling, 158 fuming, 162 stabilization of, 159 Hydrobromic acid, 151, 152, 155 constant boiling, 155... 

The methylene bridge in the fused oxazoline (203), 6-methyl-2//,6//-oxazolo[5,4,3-j/]quinolin-4-one, shows great stability towards acid cleavage, such as heating in 47% hydriodic acid. It is cleaved by oxidation, however, when treated with activated manganese dioxide in acetic acid (73JA5003). 

If the Pu(in) nitrate is not stabilized against oxidation, hydriodic acid, hydroxylamine or ascorbic and sulfamic acid may be used as a reducii agent. Problems of handling and corrosion result with HI. If appreciable Pu(IV) were present, more stringent care would have to be taken to avoid unmanageable precipitates of Pu(IV) oxalate, as discussed above. 

HI is decomposed by the action of atmospheric oxygen and light and it should be kept in brown, paraffin-coated bottles. For its stabilization 1 g of red phosphorus is added to 100 ml of hydriodic acid. One litre of water dissolves 12 moles of HI at 10°. 

Because of the stability of the complex acid, HI3, iodine is very soluble in the hydriodic acid solution, and cannot be extracted by the usual solvents, such as carbon disulfide. Treatment with hydrogen sulfide at room temperature reduces the iodine to hydriodic acid but the reaction is slow, and after several hours a yellow coloration persists. Furthermore, the liberated sulfur must be coagulated and removed by filtration prior to distillation of the product. 

For the identification of aromatic ethers use is made either of the reactivity of the aromatic nucleus (bromination, chlorosulfonation), or else they can be cleaved with hydriodic acid (see p. 201). In the latter case, however, only the alkyl group bound to oxygen is identified. The oxidation of side chains (compare p. 129) has only a limited use the alkoxy group on the aromatic nucleus increases the stability of addition compounds (see p. 126) with picric acid, which can also be used for identification. 

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