What Is Propionic Acid Solution?
Propionic acid is a short-chain carboxylic acid with the formula CH3CH2COOH (C3H6O2, molecular weight 74.08 g/mol). At room temperature it is a colourless liquid with a sharp, pungent odour. It is fully miscible with water and with most organic solvents, which is why it is commonly handled and shipped as an aqueous solution as well as in concentrated form. Its carboxyl group is the basis of both its preservative action and its reactivity as a chemical intermediate.
Main Uses of Propionic Acid
Food and feed preservation
Propionic acid and its salts - calcium propionate (E282), sodium propionate (E281) and potassium propionate (E283) - are effective mould inhibitors. In human food they extend the shelf life of bread, bakery products and cheese. In agriculture, propionic acid is applied to high-moisture grain and silage to suppress mould and yeast growth, protecting feed quality and animal health.
Chemical intermediate
Propionic acid is a key building block for cellulose acetate propionate (CAP), a plastic used in films, frames and tool handles; for herbicides, pharmaceuticals and dyes; and for propionate esters such as ethyl and butyl propionate, which are used as flavours, fragrances and solvents. It is also used as a fungicide component and as a bee repellent during honey harvesting.
Industrial uses
In industry, propionic acid serves as a solvent, a plasticiser raw material and an additive in paints, fabrics and rubber goods, demonstrating considerable versatility across formulations.
Key Properties
| Property | Value |
|---|---|
| Molecular formula | C3H6O2 (CH3CH2COOH) |
| CAS / EINECS | 79-09-4 / 201-176-3 |
| Boiling point | ≈141 °C |
| Melting point | ≈−20.8 °C |
| Density | ≈0.993 g/cm³ at 20 °C |
| Flash point (closed cup) | ≈54 °C |
| Solubility in water | Fully miscible |
| UN number | 1848 (class 8, packing group III) |
Safety, Transport and Storage
Propionic acid is corrosive: it causes burns and redness on skin contact (H314) and is harmful if swallowed (H302). Its vapours irritate the respiratory tract, and the liquid is flammable with a flash point near 54 °C, so keep it away from open flames and high temperatures. When handling, wear chemical-resistant gloves, goggles and protective clothing, and work in a ventilated area. Store propionic acid in a cool, dry, well-ventilated place in containers made of compatible materials, and transport it under UN 1848 with class 8 dangerous-goods documentation.
How to Buy Propionic Acid
Specify the concentration you need (for example 99.5% or aqueous solutions for feed treatment), the packaging format and the destination. Request a batch COA covering assay, water content and impurities, together with the SDS. Suppliers with documented quality systems such as ISO 9001:2015 and REACH registration provide the most reliable documentation for international trade.
Frequently Asked Questions
Q: What is propionic acid used for?
Propionic acid is used as a preservative in bread, cheese, grain and animal feed, and as an intermediate for cellulose acetate propionate plastics, herbicides, pharmaceuticals, dyes, fungicides and flavour esters.
Q: Is propionic acid safe in food?
Propionic acid and its calcium, sodium and potassium salts (E280–E283) are approved food preservatives within regulated maximum levels in the EU and other major markets.
Q: What is the difference between propionic acid and propanoic acid?
There is no difference: propanoic acid is the IUPAC systematic name and propionic acid the traditional common name of the same compound, CAS 79-09-4.
Q: Is propionic acid corrosive?
Yes. Concentrated propionic acid is corrosive (H314) and must be handled with gloves, goggles and protective clothing; aqueous solutions are less aggressive but still require care.
Q: Can propionic acid be used for grain preservation?
Yes. Propionic acid is widely applied to high-moisture grain and silage to inhibit mould growth, and it is also used as a feed additive to extend the shelf life of animal feed.
Q: What UN number applies to propionic acid?
Propionic acid is transported under UN 1848, hazard class 8 (corrosive), packing group III.