These two links describe denatured alcohol:
http://www.atf.treas.gov/regulations/27cfr20.pdf
http://www.atf.treas.gov/regulations/27cfr21.pdf
A sampling of special denatured alcohol formulas:
all denaturants are added to 100 gals of 95% ethanol
#1 Four gallons of methyl alcohol and either 1/8 advoirpois ounce of denatonium benzoate, N.F.,(BITREX); 1 gallon of methyl isobutyl ketone; 1 gallon of mixed isomers of nitropropane; or 1 gallon of methyl n-butyl ketone.
#3A 5 gallons of methyl alcohol
#3C five gallons of isopropyl alcohol
#23A eight gallons of acetone, U.S.P.
#23H eight gallons of acetone, U.S.P. and 1.5 gallons of isobutyl ketone.
#30 ten gallons of methyl alcohol
Formulas are restricted by use:
Solvents and thinners: 1, 23A and 30
Wood Stains: 1, 3A, 3C, 23A and 30
Solvents, special (restricted sale): 1,3A and 3C
Laquer thinners: 1 and 23A
Propietary Solvents: 1 and 3A
Rubbing Alcohol: 23H
General use of specially denatured alcohol:
Propietary solvents: 1 or 3A plus
1 part gasoline, unleaded gasoline, heptane, or rubber hydrocarbon solvent; and
3 part toluene, ethyl acetate, methyl n-butyl ketone, methyl isobutyl ketone, tert-butyl alcohol, sec-butyl alcohol, nitropropane (mixed isomers), or ethylene glycol mono ethyl ether
Rubbing alcohol is formula 23H with water and other ingredients (one additional denaturant) and optionally perfume, medicinal ingredient, and/or coloring.
Completely denatured alcohol (CDA) follows different rules and formula including that the alcohol be 80% or greater:
#18: 2.5 gallons of either methyl isobutyl ketone, mixed isomers of nitropropane, or methyl n-butyl ketone;
.125 gallons of pyronate or a similar compound;
.5 gallons acetaldol (beta-hydrobutyraldehyde); and
1 gallon of either kerosene, deodorized kerosene, gasoline, unleaded gasoline, rubber hydrocarbon solvent, or heptane
#19: 4 gallons of either methyl isobutyl ketone, mixed isomers of nitropropane, or methyl n-butyl ketone; and
1 gallon of either kerosene, deodorized kerosene, gasoline, unleaded gasoline, rubber hydrocarbon solvent, or heptane
Formulations with more than 4% methanol must be marked with the skull and crossbones and the words "danger","poisonous","vapor harmful","May be fatal or cause blindness if swallowed", and "Cannot be made nonpoisonous"
To be sold as "denatured alcohol" solvent or thinner OTC (this is my understanding) it must be a propietary solvent, completely denatured alcohol, formula 1, formula 23A, or Formula 30.
How can you tell the difference between formulations?
CDA that hasn't been processed further is listed as "Completely Denatured Alcohol". The "Caution - contains poisonous ingredients" usually indicates CDA. A variety of things can be mixed into this stuff and still be called "Completely Denatured Alcohol". However adding other stuff or higher quantities changes it to "Denatured Alcohol". Some ingredients are unique to completely denatured alcohol:
pyronate, acetaldol and kerosene.
Some ingredients are unique to propietary solvents:
toluene, ethyl acetate, tert-butyl alcohol, sec-butyl alcohol, and ethylene glycol mono ethyl ether
CDA and propietary solvents contain two other ingredients not found in the straight formulas:
heptane and rubber hydrocarbon solvent.
Denatorium Benzoate indicates a formula 1 or propietary solvent derived from formula 1.
Methyl isobutyl ketone; mixed isomers of nitropropane; or methyl n-butyl ketone, indicate that the formula isn't #30 or #23A.
The methyl alcohol content provides another method of distiguishing:
Only Formula 30 and propietary solvents from formula 3A will definitely have a warning for more than 4% Methyl Alcohol. But Formula 1 and propietary solvents derived from formula 1 may still have the warning even though they don't contain 4%. Formula 23A and CDA won't have a methyl alcohol warning.
The best alcohol is formula 30 or formula 23A. CDA or propietary solvent may be acceptable if it doesn't have kerosene, gasoline, or rubber solvent. Not all ingredients may be listed on the can. Every paint supply or hardware store should have MSDS on file. Ask for one. They are required to provide it.
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