Acetic acid

Please read this explanation about safe working with acetic acid and cleanup of spills.

Wikipedia has an article about acetic acid.

ChemicalAcetic acid
StateColourless fluid
ConcentrationAbout 5%
Fixation timeOvernight
Acid dyesImproves
Basic dyesReduced

Vinegar has been used for centuries to preserve foods by pickling. The acetic acid in vinegar was produced by fermentation using acetobacter species, often of wine or malted barley and similar materials. Laboratory and industrial acetic acid is invariably chemically produced.

The term "Glacial acetic acid" is the name of the concentrated acid which is water free. It is termed glacial because it freezes at about 16°C. Percentage solutions of acetic acid are invariably x mL of this acid diluted up to 100 mL with distilled water

Other forms of acetic acid have been used in the past, and the terms are sometimes encountered. "Pyroligneous acid" is one. This is produced by the destructive distillation of beechwood and contains approximately 5% acetic acid. A simple 5% acetic acid solution may often be substituted, but it should be kept in mind that pyroligneous acid may contain other chemicals from the beechwood which may be required. One of the myriad forms of vinegar may also be encountered. These vary from about 3% to 5% (sometimes more) of acetic acid. They may be replaced with simple acetic acid solutions.

How it fixes
Acetic acid does not have much effect on proteins, other than to enable swelling by the absorption of water. Its major effect is to precipitate DNA, which is split off from nucleoprotein. For this reason, acetic acid is valuable for the preservation of nuclei, and is often added to fixatives specifically to do that.

Carbohydrates are not affected.

Lipids are largely unaffected at the concentrations normally used.

Collagen swells and if acetic acid is used alone it shrinks badly during subsequent dehydration. Other fixing agents can overcome this, so acetic acid is invariably used in conjunction with them. In mixtures, nuclei are very well preserved, but cytoplasmic inclusions may be destroyed.

Several hours to overnight.

Simple solution
Acetic acid is not used alone for fixation but is incorporated into fixative mixtures, most commonly at a concentration of approximately 5%.

No specific aftertreatment, as it is miscible with both water and ethanol.


Baker, John R., (1958)
Principles of biological microtechnique
Methuen, London, UK.



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