The ability to purchase nitric acid (\(\text{HNO}_3\)), a potent mineral acid, depends almost entirely on the concentration and volume sought. Nitric acid is a colorless, highly corrosive liquid that acts as both a strong acid and a powerful oxidizing agent. Its aggressive nature means it can cause severe chemical burns and its vapors are hazardous when inhaled. These inherent properties, coupled with its industrial utility, place its commercial availability under significant scrutiny.
The Role of Concentration in Availability
The concentration of nitric acid is the most important factor determining its accessibility. Dilute solutions, typically less than 10% \(\text{HNO}_3\), are generally not subject to heavy regulation and can often be purchased easily. These low-concentration solutions are considered less hazardous and are not readily misused.
Commercial-grade nitric acid, commonly used in laboratories and industry, is typically sold as a concentrated solution of 68\% to 70\% \(\text{HNO}_3\). Products at this strength are heavily regulated due to their corrosive power and potential for misuse.
The highest concentrations are known as fuming nitric acid, containing over 86\% \(\text{HNO}_3\). This grade is extremely volatile and hazardous, and is the most strictly controlled. The jump in concentration significantly increases the regulatory oversight required for purchase, transport, and storage.
Common Applications and Consumer Sourcing
For the average consumer, the need for nitric acid usually centers on specialized applications met with low- to mid-level concentrations. Common uses include:
- Metal etching, particularly for copper, brass, and steel, often combined with water and alcohol to create Nital.
- Metal passivation, which removes free iron from stainless steel surfaces to create a corrosion-resistant oxide layer.
- Separating silver from gold (parting), as the acid dissolves silver and base metals but leaves pure gold untouched.
- pH adjustment in certain industrial water treatment applications, though less aggressive acids are often preferred.
Consumers seeking low-concentration solutions (e.g., 5\% to 10\%) may find them through specialized chemical supply companies or local suppliers after an inquiry about the intended use. Purchasing concentrated acid (68\% or higher) requires sourcing from a dedicated chemical distributor. These vendors implement a rigorous verification process, including proof of a legitimate business or institutional need and detailed identification checks, effectively blocking purchases by private individuals.
Legal Restrictions and Precursor Chemical Status
The legal barriers surrounding the purchase of concentrated nitric acid stem from its classification as a precursor chemical. It can be used in the illicit manufacture of controlled substances or explosives, making its distribution a matter of federal and international concern.
In the United States, the Drug Enforcement Administration (DEA) and other federal agencies closely monitor nitric acid due to its potential for diversion in clandestine operations. Concentrated nitric acid is subject to various federal regulations, including those from the Environmental Protection Agency (EPA), which mandates strict handling and reporting requirements for high-concentration solutions stored in large quantities.
Globally, concentrated nitric acid is regulated under international frameworks designed to prevent the production of explosives. This leads to strict quantity limitations and detailed transaction reporting requirements imposed on vendors. Sellers are legally mandated to maintain records of all regulated transactions, including the purchaser’s identity, the quantity sold, and the intended use. Vendors must also report any suspicious transactions to authorities, creating a significant regulatory hurdle for non-commercial buyers.
Safe Handling and Storage Requirements
Acquiring nitric acid requires a commitment to rigorous safety protocols due to its corrosive and oxidizing nature. Personal protective equipment (PPE) is non-negotiable when handling the chemical. This includes safety goggles, a face shield, and chemical-resistant gloves made of materials like neoprene, since common nitrile gloves offer little protection against high concentrations.
Work with concentrated acid must be conducted in a well-functioning chemical fume hood to prevent the inhalation of toxic nitrogen oxide fumes. Proper storage demands a cool, well-ventilated area, away from direct sunlight and heat, to minimize decomposition.
The acid must be stored separately from incompatible materials, such as organic compounds, bases, and reducing agents, to avoid violent or explosive reactions. Containers should be made of compatible materials like high-density polyethylene (HDPE) or glass, and must be placed within secondary containment trays to capture any leaks or spills.