XVI International Botanical Congess

Chloral hydrate has traditionally been used as a clearing agent for plant tissues. This compound is regulated in the United States by the Drug Enforcement Agency as a Class IV substance requiring the user to obtain a permit for the purchase and use of the compound. This has discouraged its use by small analytical labs. Over the years other clearing agents, e.g., 2-5% KOH, sodium hypochlorite, dilute HCl have been used but are not as effective as chloral hydrate. 2,2,2 trichloroethanol can be directly substituted for chloral hydrate in all clearing formulae. Chloral hydrate (trichloroacetaldehyde hydrate) is an aldehyde whereas 2,2,2 trichloroethanol is the corresponding alcohol. The same precautions must be taken when handleing 2,2,2 trichloroethanol as with chloral hydrate. The MSDS for the two compounds is similar. 2,2,2 trichloroethanol is not regulated by the DEA.