Hydrogen sulphates and selenates

Alkali hydrogen sulphates and selenates are frequently ferroelectric in their low temperature phases and may exhibit superionic behaviour and a plastic state in their high temperature phases, usually above 400-450 K. 

is the first crystal among hydrogen sulphates in which a pure though very low protonic conduction, k = 10 

Many hydrogen sulphates and selenates undergo structural phase transitions and the most interesting are CSHSO4 and NH4HSe04. 

CSHSO4. Calorimetric and spectroscopic measurements show that the phase transformations of CSHSO4 depend considerably on the thermal history of the sample and on pressure . On heating a freshly prepared 

Vibrational spectra are consistent with the X-ray diffraction results and confirm the statistical nature of the P2Jm symmetry The external 

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It is evident that telluric acid is notably different from what might be expected by analogy with sulphuric and selenic acids. One is hardly surprised, therefore, that isomorphism is exceedingly rare between the tellurates and the sulphates or selenates.3 The tellurates do not form alums, they do not as a rule form mixed crystals with the sulphates or selenates, the only fairly satisfactory case of mixed-crystal formation being with rubidium hydrogen sulphate and rubidium hydrogen tellurate. 

The di-hydrogen salt CSH2PO4 has been highlighted as a viable fuel cell electrolyte. Problems and progress have recently been assessed, and the relative merits of Cs phosphates, sulphates and selenates compared [83]. 

The purer forms of iron (wrought iron and steel) appear to be much more susceptible to this kind of reaction than cast iron.3 If the attacking acid is readily reducible by hydrogen, many secondary reactions may take place. Thus with nitric acid, oxides of nitrogen and ammonia may be evolved, whilst with selenic acid a deposit of elementary selenium is obtained (see below). When iron is exposed to the action of acids that are also powerful oxidisers—such as, for example, fairly concentrated solutions of nitric and chromic acids,—it is frequently rendered inert or passive.4 Its surface may remain perfectly bright, but the metal does not show any appreciable solution in the acid, and if removed and immersed in dilute solutions of such salts as copper and silver sulphates, no reaction takes place, although ordinary active iron would cause an immediate precipitation of the more electronegative metal. 

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