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Fixing Agent



Chemical Formula:


State: Colorless fluid
Concentration: Absolute
Fixation Time: A few hours
Aftertreatment: None
Acid Dyes: Neutral
Basic Dyes: Neutral
Additive: No
Coagulant: Yes
Hardens: Yes

Before You Begin

Please consult the following guide to safe working with this chemical fixing agent, including how to safely clean up spills.

Safety Note

Acetone is regarded as a relatively common laboratory chemical, and is frequently used as a drying agent for pipettes and other glassware. It is not generally considered to be a dangerous fluid. It can be harmful, but the circumstances needed are not usually met and it is not a major concern in histotechnology.

Its major disadvantage is that it is inflammable and must be kept away from all open flames or other ignition sources. It must be stored in an explosion-safe cabinet and should not be kept with oxidizing agents as it may form an explosive compound on oxidation (acetone peroxide). In practice, reasonable care ensures it can be used safely. Appropriate firefighting materials should always be readily available for use when appropriate, although large fires should be left for professional firefighters.

Acetone spills may be cleaned up by soaking into cloth or paper towels, then washing out the cloth and wiping down the area with a wet cloth. Other than sufficiently large quantities of water being used, no further treatment is necessary. Do ensure that the area is well-ventilated to remove all vapor. If using a fan for this, make sure it is one that is shielded for use in such situations. Ensure the cloth or towels are not just thrown into a closed container but made safe by dousing with water or by evaporation.

The disposal of used acetone may be a problem. Many jurisdictions permit small amounts to be discharged into their wastewater systems. Check with your municipality for their regulations on this. Large amounts should be stored in an explosion-safe environment and disposed of with other inflammable materials.

How it Fixes


Acetone is a non-additive precipitant fixative. It fixes proteins by dehydration and precipitation, and is almost always used alone and without dilution, often at 4°C for preservation of enzymes in paraffin sections.


These are not specifically fixed.


Lipids are not preserved and some may be dissolved.


Nuclear preservation is reasonable but both intracellular and extracellular preservation is poor. There may be vacuoles present and some constituents are destroyed. There may be considerable shrinkage overall. Acetone is not recommended as a morphological fixative. Its use should be reserved for fixation of tissue when enzymes are to be preserved in rapid paraffin processing.


For enzyme preservation, overnight at 4°C is usual. In the extremely unlikely event that histological fixation is required in acetone, several hours at room temperature for a 3 mm thick piece of tissue should be satisfactory.

Simple Solution

Acetone is rarely used as a morphological fixative because of its poor preservation, shrinkage and hardening effects. It has more use as a cold temperature fixative for enzyme preservation. Acetone is sometimes used as a dehydrant instead of ethanol. It is quite efficient at this, although more inflammable than ethanol. It can cause the same parched earth artifact that ethanol causes if tissue is inadequately fixed before dehydration.


No particular aftertreatment is needed. Tissues are either transferred to cold ethanol and xylene, then into wax, or directly to low melting point wax. Since acetone is a dehydrant, the tissue should not be transferred to water.


  1. Culling, C.F.A., (1974)
    Handbook of histopathological and histochemical techniques, 3rd ed.
    Butterworths, London. pp. 43.
  2. Burstone, M. S., (1962)
    Enzyme histochemistry and its application to the study of neoplasms.
    Academic Press, New York & London. pp. 23