What Is Formic Acid?
Formic acid, also called methanoic acid, is the simplest carboxylic acid with the molecular formula CH2O2 and the structural formula HCOOH. Its CAS number is 64-18-6 and its molecular weight is 46.03. At room temperature it is a colorless liquid with a sharp, pungent odor. It is named after ants, because ants and some bees and caterpillars secrete formic acid as a defensive chemical.
Formic acid is fully miscible with water and most polar organic solvents. It is a weak acid, but concentrated solutions are strongly corrosive to skin and many materials.
Is Formic Acid a Hazardous Material?
Yes. Formic acid is classified as a hazardous material under major chemical classification systems. The hazards fall into three main groups.
Corrosivity
Concentrated formic acid at 85 percent and above causes severe chemical burns to skin and eyes, with blistering or tissue damage on contact. Its vapors irritate the respiratory tract and mucous membranes and can cause coughing and breathing difficulty.
Acute Toxicity
Formic acid is harmful if swallowed and can damage the gastrointestinal tract and kidneys. Inhalation of high vapor concentrations can also produce systemic effects, because formic acid interferes with normal metabolism.
Combustibility
Formic acid is a combustible liquid with a flash point near 69 degrees Celsius. It will not ignite easily at room temperature, but hot vapors can burn, and the acid can react vigorously with strong oxidizers, releasing heat and gases.
Hazard Classification and Transport
In transport regulations, formic acid with more than 85 percent acid is carried under UN 1779 as a corrosive liquid, while solutions between 10 and 85 percent are carried under UN 3412. Both are assigned to packing groups depending on concentration. The substance is classified as corrosive with additional health hazard labels in the GHS system, and its handling is subject to workplace exposure limits in most countries.
Safe Handling, Storage, First Aid and Spill Response
Workers must wear chemical-resistant gloves, goggles and face protection, and handle formic acid only in well-ventilated areas. Storage should be in corrosion-resistant containers made of suitable plastic or stainless steel, kept away from oxidizers, bases and ignition sources, with secondary containment to catch leaks.
Ventilation must prevent vapor accumulation, and emergency eyewash and shower stations should be available wherever concentrated acid is used.
On skin contact, remove contaminated clothing and rinse the affected area with plenty of water for at least 15 minutes, then seek medical attention. On eye contact, rinse the eyes continuously with water and get immediate medical help. For spills, evacuate the area, use inert absorbent materials, and dispose of the waste according to local regulations. Do not add water to a large spill of concentrated acid without containment, because dilution generates heat.
Industrial Uses of Formic Acid
Despite its hazards, formic acid is widely used in industry. It preserves silage and animal feed, is used in leather tanning and textile dyeing, acts as a descaling and cleaning agent, coagulates rubber latex, and serves as an intermediate in the production of formate salts and other chemicals. These applications rely on strict process controls and trained personnel.
Frequently Asked Questions
What is the CAS number of formic acid? The CAS number of formic acid is 64-18-6.
Is formic acid corrosive? Yes, concentrated formic acid at 85 percent and above causes severe burns to skin and eyes and is classified as corrosive.
Is formic acid flammable? Formic acid is combustible with a flash point near 69 degrees Celsius, so it burns when heated but is not easily ignited at room temperature.
Why do ants contain formic acid? nts and some bees and caterpillars secrete formic acid as a defensive substance, which is how the acid got its name.
What is formic acid used for? Formic acid is used for silage preservation, leather tanning, textile dyeing, cleaning and descaling, rubber coagulation and chemical synthesis.
How should formic acid be transported? Formic acid above 85 percent is transported as UN 1779 and solutions from 10 to 85 percent as UN 3412, both as corrosive liquids with proper dangerous goods documentation.