Acetic Acid, CH2COOH Acetic acid is called glacial acetic acid because it is solid at temperatures below 17°C. It can be considered one of the oldest fixatives on record and in the 18th century vinegar (4-10% acetic acid content) was used to preserve Hydra.
Fixation Table of Contents
Glacial Acetic Acid & Tissue Fixation
In modern technics it is rarely used alone but is a frequent component of fixing soliuions. Its efficient fixing action on the nucleus and its rapid penetration make it an important part of good fixatives. It fixes the nucleoproteins, but not the proteins of the cyto plasm.
Acetic acid does not harden the tissue; actually it prevents some of the hardening that may without it be induced by subsequent alcoholic treatment. In some technics, however, acetic acid must be avoided be cause it dissolves out certain cell inclusions, such as Golgi and mitochondria.
Some lipids are miscible with acetic acid, or actually soluble in it. It neither fixes nor destroys carbohydrates. Acids in general cause swelling in tissues and in collagen in particular and by breaking down some of the cross-linkages between protein molecules and releasing lyophil radicles which associate Avith ^vater molecules. This swelling in some cases may be a desirable property of acids, coimteract ing and preventing some of the shrinkage caused by the majority of fixing chemicals. In order to curtail continued swelling after fixation with acetic or trichloracetic acid solutions, transfer the tissues to an al coholic washing solution in preference to water.