selenic acid

It is the principal oxoacid of selenium; the other being selenic acid.

In very acidic conditions, it makes selenic acid.

It dissolves in water to make selenic acid.

It is attacked only by boiling selenic acid which, as you must know, dissolves platinum readily.

Selenates and selenic acid are powerful oxidizing agents.

Selenic acid can even dissolve gold!

Selenic acid is a chemical compound.

Selenic acid is made by oxidation of selenium dioxide with hydrogen peroxide.

Sodium selenate is made by reacting sodium hydroxide with selenic acid.

The selenic acid formed when the silver is reduced is being used in the electrolysis vats as an electrolyte.

It can also be made by dehydrating (removing the water from) selenic acid with a strong dessicant, like phosphorus(V) oxide.

Treatment of selenic acid with fluorosulfuric acid gives the dioxydifluoride (b.p. 8.4 C):

It was not attacked by any acid except boiling selenic acid, since it formed a tremendous number of insoluble salts.

It corresponds to the selenic acid, HSeO, which is a strong acid and can in its concentrated form dissolve gold.

Hot, concentrated selenic acid is capable of dissolving gold, forming gold(III) selenate.

Selenoyl fluoride can be formed by the action of warm fluorosulfonic acid on barium selenate or selenic acid.

Another method of preparing selenic acid is by the oxidation of elemental selenium in water suspension by chlorine:

Like sulfuric acid, selenic acid is a strong acid that is hygroscopic and extremely soluble in water.

There are many acids containing chalcogens, including sulfuric acid, sulfurous acid, selenic acid, and telluric acid.

Selenic acid is a stronger oxidiser than sulfuric acid, capable of liberating chlorine from chloride ions, being reduced to selenous acid in the process:

They are made by reacting hydrogen peroxide with selenium(IV) oxide to get selenium(VI) oxide, which dissolves in water to make selenic acid.

Selenium trioxide may be synthesized by dehydrating selenic acid, HSeO, which is itself produced by the oxidation of selenium dioxide with hydrogen peroxide:

However, using chlorine or bromine as the oxidising agent also produces hydrochloric or hydrobromic acid as a side-product, which needs to be removed from the solution since they can reduce the selenic acid to selenous acid.

Due to the instability of selenium trioxide, it is impractical to synthesize selenic acid by dissolving selenium trioxide in water, unlike sulfuric acid, which can be synthesized by dissolving sulfur trioxide in water.

He obtained selenic acid in 1827 and showed that its salts are isomorphous with the sulphates, while a few years later he proved that the same thing is true of the manganates and the sulfates, and of the permanganates and the perchlorates.