Staining, Histochemistry and Histotechnology
(Frequently Asked Questions)
Dr. John A. Kiernan
Department of Anatomy
and Cell Biology
The University of Western Ontario
2-butoxyethanol ("Clereum") dehydrating or clearing agent
What are the properties of Clereum? (The MSDS for Clereum indicates the ingredient information as undiluted 2-butoxyethanol.)
It's good to learn that this isn't yet another secret clearing agent! According to the Merck Index, this compound (also called butyl cellosolve, or ethylene glycol monobutyl ether) is partly miscible with water. Its properties as a solvent seem to be similar to n-butanol; no doubt the higher B.P. (171C) is an advantage - it won't have n-butanol's nasty cough-making vapour.
Merck says the toxicity is similar to methyl cellosolve (anaemia, "CNS symptoms" etc; can be absorbed through skin).
The price of 2-butoxyethanol varies with the supplier (May 1997):
Fisher Scientific 4 litres $104
3 kg $42 (no purity details)
Acros Organics (seems to be part of Fisher)
sell three grades:
2.5 litres $24 (99%)
1 kg $23 (GC)
500 ml $36 (scintillation grade)
If the 99% stuff is OK for histology, perhaps the price isn't too bad. tert-butanol (99.5%; from Acros) is $67 for 2.5 litres, and n-butanol (99%) is $27 for 2.5 litres. This makes 2-butoxyethanol quite a good buy for a non-niffy not-quite-universal solvent. The similarity of its miscibilities to those of n-butanol suggests that this might be useful for dehydrating (and clearing) sections that have been stained with methyl green-pyronine, or other dyes that are easily lost with ordinary alcoholic dehydration.
John A. Kiernan
Department of Anatomy,
The University of Western Ontario,
LONDON, Canada N6A 5C1