Pertechnetic acid (HTcO₄) is a compound of

technetium Technetium is a chemical element; it has Symbol (chemistry), symbol Tc and atomic number 43. It is the lightest element whose isotopes are all radioactive. Technetium and promethium are the only radioactive elements whose neighbours in the sense ...

that is produced by reacting technetium(VII) oxide (Tc₂O₇) with water or reacting Tc metal or TcO2 with strong oxidizing acids, such as

nitric acid Nitric acid is an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...

, mixture of concentrated

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...

with

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscosity, viscous than Properties of water, water. It is used as an oxidizer, bleaching agent, and antiseptic, usua ...

aqua regia Aqua regia (; from Latin, "regal water" or "royal water") is a mixture of nitric acid and hydrochloric acid, optimally in a molar concentration, molar ratio of 1:3. Aqua regia is a fuming liquid. Freshly prepared aqua regia is colorless, but i ...

. The dark red

hygroscopic Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal or room temperature. If water mol ...

substance is a strong acid, with a p''K''_a of 0.32, as such it exists almost entirely as the

pertechnetate The pertechnetate ion () is an oxyanion with the chemical formula . It is often used as a convenient water-soluble source of isotopes of the radioactive element technetium (Tc). In particular it is used to carry the Technetium-99m, 99mTc isotope ( ...

ion in aqueous solution. The red color in solution is thought to be due to the formation of the

polyoxometallate In chemistry, a polyoxometalate (abbreviated POM) is a polyatomic ion, usually an anion, that consists of three or more transition metal oxyanions linked together by shared oxygen atoms to form closed 3-dimensional frameworks. The metal atoms are ...

, while fresh HTcO₄ is white. Use of strong enough acid solution, for example, concentrated sulfuric acid, can generate the protonated form, which then exists as the octahedral TcO₃(OH)(H₂O)₂ di

hydrate In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...

complex. In aqueous solutions the pertechnic acid is complitely dissociated and therefore it is considered as very strong acid its deviation from ideal activity being due to ion pair and triple ion formation with counter-cation of hydronium. Density and activity values of pertechnetic acid aqueous solutions at ''T'' = 298.15 K are tabulated in.

References

{{Technetium compounds Pertechnetates Mineral acids Transition metal oxoacids

See also

References