Glacial Acetic Acid
Definition
Concentrated acetic acid (near 100%), used in the Teichmann reagent to provide an acidic medium that helps oxidise haem and incorporate the halide.
- Concentration
- Approximately 99 to 100 percent acetic acid
- Role in Teichmann test
- Acidic medium promoting haemin crystal formation
- Hazard
- Corrosive; irritates skin, eyes and airways
- Naming note
- Solidifies into ice-like crystals below about 16C
Common questions
Why is acetic acid used instead of another acid in the Teichmann test?+
Acetic acid dissolves haemoglobin and, combined with a halide salt, drives formation of haemin chloride or bromide crystals under gentle heating, a reaction not reliably produced with mineral acids in this particular test.
Why is it called "glacial"?+
Concentrated acetic acid freezes into ice-like crystals at around 16C, close to room temperature in many labs, so chemists named the anhydrous form glacial to distinguish it from dilute vinegar-strength solutions.
What safety precautions apply when handling it in casework?+
It must be used in a fume hood with gloves and eye protection because concentrated vapour irritates the eyes and respiratory tract and direct contact with the liquid causes chemical burns on skin.
Related terms
- Confirmatory Test
- A test with sufficient specificity to establish the identity of a biological fluid for reporting purposes. Examples include Takayama and Teichmann crystal...
- Haemin (Chlorohemin)
- The oxidised, halide-salt form of haem produced in the Teichmann test. Haemin crystals are brown, rhomboid, and form in pairs or groups...
- Haemochromogen
- A reduced haem-nitrogenous-base complex. In the Takayama test, pyridine is the base, giving pyridine haemochromogen: pink, feathery or needle-like crystals.
- Pyridine
- An aromatic nitrogen heterocycle used as a secondary denaturant in Indian denatured spirit formulations (at 1-2% v/v). Its presence in a headspace...
- Sensitivity Limit
- The minimum amount of blood (or age/dilution of stain) at which the crystal test can still produce identifiable crystals. Below this threshold...