Hydrogen bismuth halides

Ionic compounds are usually scarcely soluble, but covalent compounds such as hydrogen halides and many organic compounds are soluble. Examples are hydrocarbons, carboxylic acids, acid chlorides, nitriles, aldehydes, ketones, alcohols, amines and nitrocompounds, but the conductivities of their solutions are very small. Many acceptor halides such as those of aluminium, titanium(IV), tin(IV), phosphorus(V), arsenic(III) and bismuth(III) as well as ferric chloride show reasonable solubilities due to interaction with liquid hydrogen sulphide. Solvates of AICI3, AlBrs, TiCl4, SnCU, BCI3 and others have been described . 

Among other reagents causing fission of tin-carbon bonds are hydrogen halides, mercury halides, bismuth halides, thallium chloride, arsenic halides, phosphorus halides, sulphuric acid, nitric acid, sulphur, sulphur dioxide, sulphuryl chloride and organic acidsis. 

A number of complex bismuth halides are weU-known, eg, disodium bismuth pentachloride [66184-10-9] Na2BiCl sodium dibismuth heptachloride [66184-09-6J, NaBi Cl and trisodium bismuth hexachlotide [66114-82-7J, Na BiCl. The acid, hydrogen dibismuth heptachloride tnhydrate [66124-39-9] HBi Cl 3H20, is a crystalline substance, stable at room temperature, that maybe isolated by cooling a solution of BiCl in concentrated hydrochloric acid to 0°C. 

Tenno and Palm[164] observed a decrease in the slope of the polarization curve for bismuth in the presence of halide ions, especially iodide ions, down to 60 mV. Later, this system was investigated in greater detail in the same laboratory[165]. It was found that in the region b - 60 mV, the overpotential is independent of the solution composition for moderately acidified solutions, while a noticeable dependence was observed for concentrated solutions. In analogy with the data for a mercury cathode (cf. sections 2.1 and 2.2), these results are considered as proof of a barrierless discharge of hydrogen ions and undissociated acid molecules respectively. 

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