Also found in: Dictionary, Thesaurus, Acronyms, Encyclopedia.
Related to HNO3: HC2H3O2

nitric acid (HNO3)

Etymology: Gk, nitron, soda; L, acidus, sour
a colorless, highly corrosive liquid that may give off suffocating brown fumes of nitrogen dioxide on exposure to air. Traces of nitric acid may be found in rainwater during a thunderstorm. Commercially prepared nitric acid is a powerful oxidizing agent used in photoengraving and metallurgy; in the manufacture of explosives, fertilizers, dyes, and drugs; and occasionally as a cauterizing agent for the removal of warts. Organic nitrates or polyol esters of nitric acid such as nitroglycerin and amyl nitrite are effective vasodilators often used in relieving angina, but exactly how they function in dilating arterial and venous smooth muscle is not yet understood. Historically known as aqua fortis.


Formula for nitric acid.
CAS # 7697-37-2

nitric acid

; HNO3 strong, self-limiting, oxidizing agent (see Table 1)
Table 1: Keratolytic and caustic agents
Keratolytic/caustic agentIndicated use
Whitfield's ointment (3% salicylic acid and 6% benzoic acid in white soft paraffin)Treatment of mild tinea pedis
5% salicylic acid ointmentApplied daily for 7 days to soften hyperkeratosis and facilitate its removal
12% salicylic acid in collodionMacerating agent; painted over callosity and left in situ for 7 days, to assist removal of heavy callosity
20-40% salicylic acid plasterApplied topically and left in situ for 1-2 days to aid removal of corns
40-70% salicylic acid ointmentApplied topically in a cavitied pad and left in situ for 7 days for verruca treatment; the lesion should be masked
Calmurid cream (10% urea)To hydrate anhidrotic skin; applied daily to treat dyskeratosis
40% urea creamA strongly keratolytic agent, applied under an occlusive dressing and left in situ for 7 days, to soften, macerate and aid the reduction and removal of hypertrophied nails in patients who are unsuitable for nail avulsion
Monochloroacetic acidA deeply penetrating caustic that is painful in use Applied, retained in situ and reviewed within 3-7 days, for the treatment of verrucae:
1. as a saturated solution to the lesion
2. as a tiny crystal strapped over a masked lesion
3. as a tiny crystal embedded in 40-70% salicylic acid retained by a cavitied pad
Trichloroacetic acidA self-limiting caustic with a superficial action
Applied directly to the verruca, after initial scalpel debridement of the lesion
May be used in conjunction with 75-95% silver nitrate (see below) as a diagnostic or a final treatment of verrucae
75-95% Silver nitrateA self-limiting caustic with a superficial action, causing a dark brown discoloration of the skin to which it is applied; it is used for the treatment of shallow or mosaic verrucae.
Note: Some patients show an idiosyncratic local sensitivity or inflammatory reaction to applied silver nitrate
1. Applied directly to the lesion, after overlying callosity has been debrided off
2. Applied directly to the lesion in alternating layers with trichloroacetic acid
3. As a diagnostic aid to identify verrucous tissue; viral-infected skin cells show up as bright white dots within a few moments of the application of the layers of silver nitrate and trichloroacetic acid
Potassium hydroxide (KOH)A powerful keratolytic caustic with a great affinity for water that penetrates deeply dissolving precipitated protein; used to destroy soft tissues
1. Overlying hyperkeratosis is debrided off the verruca and the foot is immersed in water for 5 minutes to hydrate the skin, then dried; a KOH pellet is rubbed into the lesion; the foot is reimmersed in water and the jelly-like material formed by the KOH on the lesion surface is debrided off. The process is repeated once or twice until the lesion appears to have gone, then glacial acetic acid is applied to neutralize the KOH
2. A similar protocol may be used to ablate nail matrix after removal of the overlying section of nail plate
3. KOH 5% liquid applied to heavy callosity and left in situ for 5 minutes softens heavy callosity to ease its removal
Pyrogallol (pyrogallic acid)A powerful analgesic, non-self-limiting, caustic reducing agent. It may be used in the treatment of recalcitrant verrucae or neurovascular corns in areas of skin overlying a healthy layer of fibrofatty padding. It should only be used with great caution as its action continues after application has ceased and can lead to severe tissue breakdown that is slow to heal. It is incompatible with alkalis, iron salts, oxidizing agents and ammonium salts
1. 20% pyrogallol ointment for the treatment of neurovascular corns
2. 40% pyrogallol ointment for the treatment of VP
3. WP ointment (20% pyrogallol, 20% wheat germ oil) for the treatment of tough, fibrous, hyperkeratotic plantar lesions
PhenolAn analgesic, corrosive caustic. It is used as an 80% solution (liquefied phenol) to destroy soft-tissue lesions such as VP, or nail matrices (three applications, each of 1 minute duration). Its action is quenched by dilution with IMS or isopropyl alcohol. Healing is delayed for several weeks after its application
Glacial acetic acidA weakly acidic mild caustic that is crystalline at 14°C
1. As a paint to hard or vascular corns, or VP (return period 14-21 days)
2. As a paint to VP, alternating with silver nitrate 75% (in a similar manner to trichloroacetic acid)
3. To neutralize KOH (see above: KOH, point 1)
Nitric acidA powerful analgesic oxidizing caustic agent with a superficial action that offers a 'one-off' VP treatment
1. Applied to VP with a glass rod and left in situ for 5 minutes, followed by phenol solution 10%; the skin stains bright yellow
2. The lesion is saturated with phenol solution 5% for 5 minutes, then with nitric acid for 20-30 seconds, then once again with phenol solution 5%
Strong iodine solution (iodine solution 10%; iodine fortis)A strong astringent and vesicant agent. It is incompatible with many topical medicaments, and can cause sensitivity reactions in some patients
1. to shrink nail tufts
2. to shrink hypergranulation tissue
FormaldehydeA strongly astringent and antiseptic agent used in the treatment of VPs (the skin surrounding the lesion should be protected with petroleum jelly; sensitivity is likely)
1. 10% formaldehyde in collodion, painted on daily
2. 36% formaldehyde solution, painted on daily
Thermal caustics
CryosurgeryThe topical application of liquid nitrogen (at -196°C) or nitrous oxide (at -88.5°C) to destroy small soft-tissue lesions; the cell cytoplasm must be reduced to and maintained at -24°C or lower for at least 1 minute, and repeated for two further freezing episodes between which the area has been allowed to thaw. Cryosurgery is more effective when any overlying hyperkeratosis is removed before freezing
HyfrecationTissue destruction by initial fulguration (outlining and superficial charring) of the lesion by the application of high-frequency electrical energy), then electrodesiccation (electrocautery) of the lesion by the release of electrical energy whilst the probe is inserted into the lesion
ElectrosurgeryTissue removal using high-frequency energy waves to incise through tissue

Note: Please also refer to the text entries for each listed agent.

IMS, industrial methylated spirit; VP, verrucae pedis.

Mentioned in ?
References in periodicals archive ?
Furthermore, a blank sample was also prepared simultaneously by transferring 10 mL of concentrated HNO3 acid to one of the empty microwave vessels and placed it in the microwave system after it was sealed tightly.
The metallographic cut was mechanical grinded and polished, chemical etched in 3% HNO3 alcohol solution.
After annealing the samples were subjected to surface passivation treatment, carried out in a solution of 20% HNO3 for 15 min at 600C.
It must allow the treatment of the plates with several different types of chemistry (HNO3 / HCl / DI water, HF, HNO3 / HF, H202 / H2SO4 / DI water, etc.
Table 121: Leading Manufacturers of HNO3 in South Africa
In our previous study, an enriched in kerogen sample of Goynuk oil shale (GOS-R) was prepared by treating with HCl, HNO3 and HF acid [3].
0 g powder of each sample was digested with 10 N HNO3, and for determining sodium (Na) and K contents, a flame photometer (model, JENWAY-PFP7) was used.
On the other hand, upon treatment with HNO3 acid, a new adsorption band emanates with the characteristic absorption peak of carboxylic acid at 3358 cm"1.
fast piece test extraction from electrolytic bath, drying and metallographic attack with 2,3% HNO3 to distinguish the microscopically structure of that;