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Dehydrant for Paraffin Wax Processing

Acetone is quite inflammable, more so than the other dehydrants given, and is really unsuitable for routine dehydration. It has an intrusive odor and evaporates rapidly, which increases the fire risk unless the containers are tightly capped. It is an effective dehydrant and some technologists have used a final acetone bath following ethanols to ensure complete dehydration. This is not necessary if enough changes of a safer dehydrant are used.

It should be noted that some automatic tissue processors have seals or gaskets which may be damaged by acetone, particularly if used with heat. This must be investigated before using it.

Acetone may also be used as a fixing agent. It has had some use at 4°C for brief fixation of thin slices of tissue for enzyme histochemistry on paraffin sections, but is otherwise not recommended. As with ethanol, acetone does not refix tissues during dehydration if they have been properly fixed with other agents, but it will complete fixation if it was not completed properly in a fixative. It is a very poor quality fixative for this, particularly if it has been warmed to assist dehydration. It may be avoided by always ensuring that tissues have been properly fixed before dehydration is started.

Acetone is not intolerant for fixed tissue, but it should not be used for long periods.

Acetone has been recommended as a wax antemedium, permitting infiltration without using a clearing agent. This can be done, but the resulting blocks are not particularly well infiltrated. Isopropanol is a much better choice.