“Glacial acetic acid” is a name for water-free (anhydrous) acetic acid. Similar to the German name “Eisessig” (“ice vinegar”), the name comes from the solid ice-like crystals that form with agitation, slightly below room temperature at 16.6 °C (61.9 °F).
Acetic acid can never be truly water-free in an atmosphere that contains water, so the presence of 0.1% water in glacial acetic acid lowers its melting point by 0.2 °C.
How Glacial Acetic Acid Is Different
Acetic acid that contains a very low amount of water (less than 1%) is called anhydrous (water-free) acetic acid or glacial acetic acid. The reason it’s called glacial is because it solidifies into solid acetic acid crystals just cooler than room temperature at 16.7 °C. Removing the water from acetic acid lowers its melting point by 0.2 °C.
Glacial acetic acid may be prepared by dripping acetic acid solution over a “stalactite” of solid acetic acid (which could be considered to be frozen). Like a water glacier contains purified water, even if it’s floating in the salty sea, pure acetic acid sticks to the glacial acetic acid, while impurities run off with the liquid.
Caution: Although acetic acid is considered a weak acid, safe enough to drink in vinegar, glacial acetic acid is corrosive and can injure skin on contact.
Difference Between Acetic Acid and Glacial Acetic Acid
The principal difference between acetic acid and glacial acetic acid is how much water it contains. But, there are other differences.
| Acetic Acid | Glacial Acetic Acid |
| Acetic acid is a main component of vinegar apart from water and other trace elements. | Glacial acetic acid is nothing but a concentrated form of acetic acid solution. |
| solution of acetic acid in water | concentrated acetic acid containing very little water |
| Acetic acid contains more water and is in its diluted form. | Glacial acetic acid has less than 1% of water content and is concentrated. |
| safe in food or on skin | highly corrosive, irritates and injures eyes, skin, and mucous membranes |
| does not freeze under ordinary storage conditions | forms ice-like crystals under cool storage conditions |
| naturally-occurring | usually synthesized in a lab |
| commercially produced by carbonylation of methanol using a rhodium-iodine catalyst | obtained by solidifying acetic acid around a “stalactite” of glacial acetic acid |
| Acetic acid is produced via rhodium-iodine catalysed carbonylation of methanol. | Glacial acetic acid is obtained by dipping acetic acid solution in a “stalactite” of solid glacial acetic acid. |
| Acetic acid is naturally occurring and found in plants and animal organisms. | It is usually manufactured in a lab. |
While many organisms produce acetic acid, both the regular variety and glacial acetic acid are petroleum products commercially. It’s also widely recycled. For example, around 1.5 metric tons of the global use of 6.5 metric tons is recycled chemical.
Dilute acetic acid is a source of glacial acetic acid because pure acetic acid stick to “stalactites” of solid glacial acetic acid. This is comparable to the way fresh water forms over icebergs in a salty sea. For example, dripping vinegar over frozen glacial acetic acid further dilutes the vinegar while growing the amount of glacial acetic acid.
Is glacial acetic acid the same as vinegar?
Vinegar is about 4-6% acetic acid in water. More concentrated solutions can be found in laboratory use, and pure acetic acid containing only traces of water is known as glacial acetic acid. Dilute solutions like vinegar can contact skin with no harm, but more concentrated solutions will burn the skin.
Acetic Acid and Ethanoic Acid Naming
The IUPAC name for the chemical is ethanoic acid, a name formed using the convention of dropping the final “e” in the alkane name of the longest carbon chain in the acid (ethane) and adding the “-oic acid” ending.
Even though the formal name is ethanoic acid, most people refer to the chemical as acetic acid. In fact, the usual abbreviation for the reagent is AcOH, partly to avoid confusion with EtOH, a common abbreviation for ethanol. The common name “acetic acid” comes from the Latin word acetum, which means vinegar.
Acidity and Use as a Solvent
Acetic acid has an acidic character because the hydrogen center in the carboxyl group (-COOH) separates via ionization to release a proton:
CH3CO2H → CH3CO2− + H+
This makes acetic acid a monoprotic acid with a pKa value of 4.76 in aqueous solution. The concentration of the solution greatly affects the dissociation to form the hydrogen ion and the conjugate base, acetate (CH3COO−).
At a concentration comparable to that in vinegar (1.0 M), the pH is around 2.4 and only around 0.4 percent of the acetic acid molecules are dissociated. However, in very dilute solutions, over 90 percent of the acid dissociates.
Acetic acid is a versatile acidic solvent. As a solvent, acetic acid is a hydrophilic protic solvent, much like water or ethanol. Acetic acid dissolves both polar and nonpolar compounds and is miscible in both polar (water) and nonpolar (hexane, chloroform) solvents. However, acetic acid is not fully miscible with higher alkanes, such as octane.
Application & Usage Of Glacial acetic acid
- Glacial acetic acid is used as a condiment and acidity regulator in the food industry. It is also utilized for the production of vinegar.
- Glacial acetic acid used to manufacture acetic anhydride, vinyl acetate monomer, acetate ester, and purify terephthalic acid.
- In the textile industry, ethanoic acid is widely used for printing and processing.
- Glacial acetic acid(CH3COOH) is used to produce synthetic fibers, like rayon and cellulose acetate.
- In the personal care industry, acetone, perfumes, and esters are produced from acetic acid.
- In different industries, glacial Acetic acid use as a solvent in photographic film, in transforming rubber from latex, preparation of dyes and inks, manufacture of substrates, fabrication of polyvinyl acetate for wood glue, production of white lead, manufacture of pesticides, and to produce soft drinking bottles.
- To test blood, clinical laboratories glacial Acetic acid use.
- To preserve and canning pickles and other vegetables, diluted ethanoic acid is used.
- In the medical industry, diluted glacial acetic acid can help to prevent or cure fungal or bacterial outer ear infections.