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Nitric acid, a danger lurking

Nitric acid is a strong acid, found in the nature in salt forms (nitrates), with the formula HNO3.

Nitric acid is a strong oxidant that attacks almost all metals.

By its ability to separate the gold from silver upon dissolution of this, it was once known as “aqua fortis”.

Aqua fortis should not get mixed up with “aqua-regia”, which is a mixture of nitric acid and hydrochloric acid at a ratio of one part nitric acid for three parts of hydrochloric acid which presents this designation because it dissolves gold, the king of metals.

In the past, nitric acid was obtained by adding sulphuric acid to nitrate salts such as sodium nitrate (NaNO3). Among the many technical applications, there is the nitrification of organic compounds (manufacture of explosives, artificial fertilizers, pulp and varnishes).

Synonyms : Aqua fortis; Azotic acid; Nitric acid

Properties of nitric acid

The production of nitric acid is extremely polluting, releasing gases that contribute to outbreak of acid rain and greenhouse effect worsening.

Nitric acid, among its peculiarities, becomes an offending agent extremely peculiar, delegating a sui generis aspect, as the skin reaction of xantochromia (yellowish appearance of the skin after a certain contact time, resulting from reaction with cysteine of our skin).

During this phenomenon, the deepening and worsening of the lesions are clear, as well as the progressive and the end aspects, turning an injury apparently superficial in a 3 degree burn in a few hours or days. Washing with water, acting by mechanical removal but also by dilution, which facilitates in a manner that an aggressor goes deeper into the skin, rinsing is not enough and acid reactivity is not stopped, worsening injury more. In the case of a contact time greater than one minute and consequently, a deeper corrosive attack, the use of Diphoterine® solution can and should be extended for longer, so there is a more active and deep penetration, seeking to block the intracellular sub-epidermic chemical process reaction development.

In dermatological surgery the nitric acid is used to cauterize warts and corns, causing a gradual and 3rd degree burn in a controlled manner, with good results.

All aggression by nitric acid even being properly decontaminated with Diphoterine® solution, should be observed for about 5 to 7 days, because of these peculiarities (progressive injuries).

Dr Carlos Yoshimura,
Plastic Burn Surgeon and Intensive Care, Cubatao – Sao Paulo, Brazil