Histology FAQ

Staining, Histochemistry and Histotechnology

(Frequently Asked Questions)


Dr. John A. Kiernan
Department of Anatomy and Cell Biology
The University of Western Ontario
London, Canada



FAQ Home > Processing, Decalcifying, Embedding


Xylene substitutes: what are they?


What are the various liquids sold as substitutes for xylene, and are they really safer and just as good?


There are two classes of xylene substitutes: limonenes and aliphatics.

Limonenes are prepared by steam distillation of orange peels. They are terpenoids rather similar to turpentine. They are becoming more expensive and difficult to obtain. Their great disadvantage is the persistent citrus smell, which many people find intolerable. They are difficult to distil. On the other hand, they are rather minimally toxic, and are easy to dispose of. Various brands are interchangeable.

Aliphatics are synthetic hydrocarbons with about the molecular weight of naphtha. They are odorless, not very toxic, and easily distilled. They are as difficult to dispose of as xylene.

There are at least six brands of aliphatics, and they are NOT interchangeable with each other. They vary consierably in flash point, and they all have different distillation routines. Richard Allen's Clear-Rite is perhaps the best known of them. Some of the ones offered by ma-and-pa solvent repackagers are quite unsatisfactory.

Bob Richmond, Samurai Pathologist
Knoxville TN