As A Dehydrant
Some jurisdictions restrict the availability of pure ethanol as it is the main constituent of liquors and a common recreational drink. From concern about this for religious or taxation reasons, restrictions are sometimes placed on its availability. In those cases industrial methylated spirits is often used as a substitute. This is ethanol to which some methanol and perhaps some other chemicals and dyes have been added to make it unpalatable. It may be referred to as denatured alcohol when materials other than methanol have been added.
Methanol is poisonous and the amount in methylated spirits is sufficient to cause significant harm if ingested. Methylated spirits is quite satisfactory for dehydration of tissue blocks. It also is usually available as both 96% and absolute spirits, and they may be substituted freely for ethanol.
It is occasionally used as a fixative, and is much like ethanol in this regard. When used for dehydration, it responds to unfixed tissues in much the same manner as ethanol and tissues should be properly fixed before it is applied.