Principal investigators planning to use nitric acid should follow safe use and storage practices, develop an SOP and provide documented training to all lab personnel.
The hazards
Nitric acid is a highly corrosive mineral acid and strong oxidizer used primarily for nitration of organic molecules and washing glassware or metal equipment. Nitric acid reacts violently with alcohols, alkalis, reducing agents, combustible materials, organic materials, metals, acids, cyanides, terpenes, charcoal, and acetone. It produces exothermic reactions, as well as toxic, corrosive, and flammable vapors. Nitric acid can be extremely hazardous in cases of inhalation (lung corrosive), skin contact (corrosive, irritant, permeator), eye contact (corrosive), or ingestion. The violent, reactive nature of nitric acid has led to major incidents at research universities including Tufts, Texas Tech, and at the University of Washington.
Incidents at the UW
There have been two separate waste container explosions at the UW. Luckily, no injuries resulted from these incidents; however, there were chemical spills and broken glass to clean up. Proper handling, storage, and disposal of nitric acid are key to avoiding similar incidents (or worse) in the future.
Reduce your risk
Environmental Health & Safety recommends that labs planning to use nitric acid do a risk assessment to determine whether nitric acid is really needed for their project or process. Vendors offer various cleaning products that may be used as an alternative for glassware washing, and citric acid is a common alternative for metal cleaning. If you determine it is necessary to use nitric acid:
- Use the Nitric Acid SOP template provided by Environmental Health & Safety to develop a standard operating protocol (SOP), and be sure to specify details for waste practices.
- Provide training to all lab personnel and students.
- Follow safe use and storage practices to help avoid a nitric acid incident, including:
- Minimize or eliminate use and storage of nitric acid whenever possible.
- Use in ventilated areas and in proximity to eyewash and safety shower stations, while wearing compatible gloves, safety goggles, and a lab coat.
- Avoid contact with metals! Nitric acid is extremely corrosive in the presence of aluminum, copper, and oxides and attacks all base metals.
- Store in glass containers that are secured, dry, cool (<23'C/73.4'F), away from sources of ignition, combustible materials, other acids, bases, cyanides, and acetone.
- Use secondary containers to segregate nitric acid from other acids in your acids cabinet.
- Storage containers must be dry, as nitric acid can react with water or steam to produce heat, and toxic, corrosive, and flammable vapors.
- Pre-labeled and dated safety-coated glass bottles (PTFE) may be used for nitric acid waste; avoid using empty organic solvent bottles.
- Proper waste segregation can help avoid laboratory accidents and explosions.
- Do not mix nitric acid waste with any other waste streams, including other inorganic acids.
- Segregation of nitric acid waste from different processes or experiments is recommended.
Spills
In the case of a spill, absorb nitric acid with an inert dry material (earth, sand, or other non-combustible material), place in an appropriate waste container, and neutralize with dilute sodium carbonate.
Responsibility for safety
Principal investigators and/or lab managers are responsible for ensuring all laboratory personnel understand and adhere to safety requirements in the laboratory.
- Following safety protocols in the UW Laboratory Safety Manual will help researchers and facilities avoid the health and economic costs of nitric acid accidents.
- Follow the guidance in the Nitric Acid Safety Focus Sheet and contact the EH&S Lab Safety Team for more information on preventing nitric acid incidents.