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Fixing Agent



Methyl alcohol
Methyl hydrate

Chemical Formula:


State: Colorless fluid
Concentration: Absolute
Fixation Time: Several 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

Methanol is not generally considered to be a dangerous material. It can be harmful, even cause death, but this is almost unheard of in a laboratory. If ingested, methanol is converted into formaldehyde and may lead to blindness or death. Medical treatment is essential and must be given immediately, without delay.

It is inflammable and burns with a pale flame. Sometimes this flame is difficult to see and burns may result accidentally. Exercise caution if methanol is used as a fuel and ignited. Firefighting materials should always be readily available for use when needed, although large fires should be left for professional firefighters.

Methanol 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.


Methanol is the simplest of the alcohols and the fixative traditionally used for blood smears to be stained with Romanowsky stains. It has also been recommended as a substitute for ethanol in Carnoy’s fluid, which is then called “methacarn”. Other than that, it is not usually used as a fixative for tissues to be examined by light microscopy.

How it Fixes


The fixation obtained with methanol is very similar to that of ethanol. It is a non-additive precipitant fixative. It fixes proteins by dehydration and precipitation. Mixtures incorporating it are usually water free.


These are not specifically fixed but may be precipitated along with proteins.


Lipids are not preserved and some may be dissolved.


Nuclear preservation is satisfactory, but cytoplasmic preservation is only fair as some constituents are destroyed. There may be considerable shrinkage overall.


Several hours for a 3 mm thick piece of tissue should be satisfactory. Thinner tissues such as fine needle biopsies will be fixed within an hour or two.

Simple Solution

Methanol is rarely used alone as a fixative for tissue, but it is the most common fixative for blood and bone marrow aspirate smears.


No particular aftertreatment is needed. Since it is a dehydrant, tissues are appropriately transferred to a clearing agent directly or to absolute ethanol if dehydration is not complete.


  1. Kiernan. J.A., (1999)
    Histological and histochemical methods: Theory and practice, 3rd ed.
    Butterworth Heinemann, Oxford, UK. pp. 14 – 15