Alcohol from Wal-Mart? When all else fails, read the label, which should 
state whether the alcohol is 95% or absolute alcohol.

There is no single "denatured" alcohol - there are at least 40 denaturing 
formulas approved by - I think it's the Bureau of Alcohol, Tobacco, and 
Firearms (Treasury) - with everything from poisons to bad smells to yucky 
looking dyes. The "reagent alcohol" commonly used in histology is S3DA 
modified (90% ethanol, 5% methanol, 5% isopropanol), with denaturation with 
methyl isobutyl ketone (MIBK) also used (acceptable if you can stand the 
smell). Alcohol denatured with acetone is unsuitable for histologic purposes. 
"Rubbing alcohol" is usually 70% isopropanol, 30% water.

Alcohol from the liquor store? That's going to be 95%, and you have to pay 
the very high beverage alcohol tax on it. (A few labs use pure ethanol, and 
are required to maintain security procedures and to undergo BATF inspections. 
The hospital pharmacy needs a large secure storage space to make this 
practical.)

Xylene at Lowe's? I don't know anything about specifying xylene.

We pay inflated prices for ordinary products when we use them in the health 
care world. Circumventing this mark-up by buying industrial solvents may be 
the wave of the future. Meticulous specification of standards is the only way 
labs can defend themselves from real trouble here.

Bob Richmond
Samurai Pathologist
Knoxville TN