What Is Formic Acid?
Formic acid, systematically named methanoic acid, is the simplest carboxylic acid. Its CAS number is 64-18-6 and its formula is CH2O2. It is a colorless liquid with a sharp, penetrating odor, and it is one of the strongest simple organic acids in terms of acid strength. Formic acid is a basic building block in organic chemistry and finds use in agriculture, leather, textile, rubber, pharmaceutical and metal-treatment industries.
The table below lists the properties most often reviewed when specifying the material.
| Property | Typical value |
|---|---|
| Appearance | Clear colorless liquid |
| Formula | CH2O2 (HCOO−H) |
| CAS number | 64-18-6 |
| Molar mass | 46.03 g/mol |
| Density at 20 °C | about 1.22 g/cm³ |
| Boiling point | about 101 °C |
| Common commercial grades | about 85%, 94% and 99% |
| Character | Corrosive; strong, sharp odor |
Grades are normally described by concentration, for example 85 percent, 94 percent and 99 percent, with the more concentrated grades favoured where water must be minimized. Because the material is corrosive, specification and packaging are usually agreed together with the required concentration and impurity limits.
Agriculture and Animal Feed Applications
Formic acid is used as a preservative for silage and stored grain in markets where such use is authorized by local feed regulation. At controlled doses it inhibits the growth of mould and spoilage bacteria and helps maintain feed quality during storage. Users must follow the approved application rates and legal requirements for feed additives in their own market, since direct efficacy claims must be supported by the relevant authorizations.
Leather and Textile Industry Uses
In leather processing formic acid is used for deliming, pickling and acidification after liming. It helps control pH during tanning and dyeing and reduces mildew on stored hides. In textile dyeing it acts as an acidifying and neutralizing agent for dye baths, improving color yield and levelness in acid and reactive dyeing of nylon and other fibers.
Rubber, Metal Treatment and Chemical Synthesis
Formic acid is used as a coagulant in the production of natural rubber latex and in the regeneration of waste rubber. It also serves as a metal surface treatment agent for cleaning and pickling, and as a solvent and auxiliary in rubber compounding. In organic synthesis it is used to prepare formate esters, formamide and its derivatives and pharmaceutical intermediates, and it acts as a hydrogen donor in transfer hydrogenation reactions.
Safety, Handling and Storage
Formic acid is corrosive and can cause severe burns to skin and eyes; it is harmful if inhaled or swallowed.
Wear acid-resistant gloves, goggles and protective clothing and work in a well-ventilated area.
Store in corrosion-resistant containers away from alkalis, oxidizers and heat.
On contact, rinse the affected area with plenty of water and seek medical attention promptly.
Keep containers closed when not in use and label them clearly, since the material is easy to confuse with less aggressive acids.
Frequently Asked Questions
Q: What is formic acid?
Formic acid, or methanoic acid, is the simplest carboxylic acid, with the CAS number 64-18-6 and the formula CH2O2.
Q: What are the main industrial uses of formic acid?
It is used for silage and grain preservation, leather and textile processing, rubber coagulation, metal surface treatment and organic synthesis.
Q: Is formic acid used to preserve silage?
Yes. In markets where it is authorized by feed regulation, it is applied at controlled doses to inhibit mould and spoilage bacteria in stored feed.
Q: Is formic acid the same as methanoic acid?
Yes. Methanoic acid is the systematic name for formic acid; both refer to the same CAS 64-18-6 material.
Q: How is formic acid used in the leather industry?
It is used for deliming, pickling, pH control during tanning and dyeing, and for reducing mildew on stored hides.
Q: How should formic acid be handled safely?
Wear acid-resistant gloves, goggles and protective clothing, work in a ventilated area, and store the product away from alkalis, oxidizers and heat.