Denatured Alcohol

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By C.H. Breedlove Question: What do mouthwash, Sterno, aftershave, hair spray, gasoline, perfume, many antiseptics, bug repellent, and shellac thinner all have in common? Answer: Alcohol.

All the products mentioned above, plus thousands of others, contain ethyl alcohol, C2H5OH. Because it is the alcohol in alcoholic beverages, ethyl alcohol is the most widely known member of the large chemical family of alcohols. Confusingly, ethyl alcohol is known by many names including ethanol (its official chemical name), grain alcohol, distilled spirits, spirits of wine, and cologne spirits. Deliberately maltreated The ethyl alcohol used in making commercial products such as aftershave and insect repellent is not pure alcohol but a special mixture designed to make it unfit for use as a beverage. It is referred to as denatured alcohol, and millions of gallons of it are manufactured each year. If you look at a label closely you may see “S.D.A. Alcohol 40 (14%).” The number in parentheses is the percent of ethyl alcohol, by volume, in the product. The S.D.A. (specially denatured alcohol) number indicates which government-approved formulation (chemical recipe) was used when the ethyl alcohol was mixed with other chemicals. The United States, as well as most other nations, places a substantial tax on the ethyl alcohol that is used in alcoholic beverages. The U.S. tax varies depending on whether the beverage is beer, wine, or distilled spirits. The highest tax is placed on “distilled spirits,” such as bourbon, gin, vodka, and rum, and is currently $12.50 per “proof gallon.” A proof gallon is 50% alcohol, 50% water. At this level of taxation, 25% to 60% of the retail price of a bottle of distilled spirits goes to the federal treasury. The imposition of an excise tax on whiskey by the federal government did not meet with great public approval when it was proposed by Alexander Hamilton, the first Secretary of the Treasury, in 1791. In fact, the Scotch-Irish citizens of southwestern Pennsylvania were so angered at this legislation that they refused to pay the tax on a product that, in their rural communities, was commonly used as a medium of exchange. The federal government called out a somewhat reluctant militia, which marched northwestward to fight some brief skirmishes with the delinquent taxpayers in what became known as the “Whiskey Rebellion” of 1794. Fortunately there were few casualties, and the federal government established its prerogative to collect a tax on alcohol. Even today state and local governments derive additional revenues from alcohol taxes, often called “sin taxes.” Many-sided molecule Because ethyl alcohol is an excellent solvent for many organic and inorganic compounds, it is widely used in cosmetics and toiletries. It is also a reactant in the synthesis of many other organic compounds. Because of its relatively high combustion temperature, it is used as a cooking fuel, either in liquid form by boaters or in jelled form (Sterno) by campers. Ethyl alcohol can be mixed with gasoline to form gasohol (90% gasoline, 10% ethyl alcohol). Many refineries routinely add smaller percentages of ethyl alcohol to help raise the octane rating of gasoline. To serve these needs, 236 million gallons of denatured alcohol were produced in the United States in 1989. That’s disgusting In order to make ethyl alcohol unfit for human consumption, and therefore free of the tax, it must be “denatured” before it leaves the distillery or the petrochemical plant where it is produced. The U.S. government has selected 97 different denaturants either for their toxicity (in the case of the “completely denatured” alcohols) or for their exceedingly unpleasant taste or odor. In either instance, the idea is to purposely render the ethyl alcohol unfit for drinking without impairing its usefulness for other purposes. The denaturants chosen obviously must be soluble in the alcohol and should also be very difficult to remove by common physical or chemical separation techniques such as distillation, solvent extraction, or precipitation. At the present time in the United States, there are about 60 different formulas that are allowed by the Bureau of Alcohol, Tobacco, and Firearms to be used as denaturants. If an alcohol manufacturer uses one of these approved formulas, he pays no tax on the alcohol sold. As an example of a completely denatured alcohol, S.D.A. Formula 1 calls for adding five gallons of toxic methyl alcohol (wood alcohol) to 100 gallons of 95% ethyl alcohol (which contains 5% water). The manufacturer is allowed some freedom of choice in many of the S.D.A. formulations, but a copy of the formulation selected, along with the label, must be approved by the government before the product can be sold. S.D.A. Formula 40 is commonly used as a solvent in toiletries, shampoos, soaps, cleaning solutions, external pharmaceuticals, and biocides. Over 39,000,000 gallons of it were manufactured in the United States in 1989. In the Code of Federal Regulations, Part 27, the composition of S.D.A. Formula 40 is described as follows:

To every 100 gallons of ethyl alcohol of not less than 185 proof add 1.5 avoirdupois ounces of brucine (alkaloid) or brucine sulfate, or quassin, or 1.5 avoirdupois ounces of any combination of these denaturants and 1/8 gallon of tert-butyl alcohol.

Certainly not appealing ingredients! Toxic or noxious Mouthwashes can contain alcohol as a solvent for their other ingredients. However, one clearly cannot put a toxic substance in a product that might be swallowed. On the other hand, it makes no sense to add denaturants that are so repulsive that no one can stand to use the mouthwash. (I once was asked to taste-test a product containing a tiny amount of the denaturant quassin, an extract from a South American plant. This material left a bitter taste that lasted for half an hour in my mouth. Afterwards, I looked up the compound in The Merck Index and found that its bitterness threshold is one part quassin in 60,000 parts of water. This makes quassin twice as bitter as quinine.) Occasionally, mouthwash producers try to get the government to approve a product that a consumer might use as a beverage. Once a formula for a crème de mentheflavored mouthwash was submitted for approval. Another mouthwash flavoring was to be crème de cacao. Both samples were so close to being alcoholic beverages that they were rejected by the Bureau of Alcohol, Tobacco, and Firearms and never made it to the supermarket shelves. The next time you read the label of some high-priced product and see an S.D.A. number, imagine how much you would pay for this product if the ethyl alcohol it contains were not denatured! CAPTIONS

It only costs about $1.50 to make a gallon of ethyl alcohol ($.40 per liter), but if the alcohol is to be used in a beverage, a federal tax of $25 per gallon ($6.60 per liter) is added.

Figure 1. Ethyl alcohol, C2H5OH, is one of the most widely used chemicals, but it is seldom used in its pure form. Because it is difficult to separate from water, chemists often use the less expensive mixture of 95% alcohol and 5% water. Also, when used as a solvent it is first denatured — mixed with toxic or noxious substances — to make it unfit for use as a beverage and therefore not subject to liquor taxes.

BIOGRAPHY

C.H. Breedlove is a professor of chemistry at Montgomery College, Rockville, MD. The author thanks the chemists at the National Laboratory Center at the Bureau of Alcohol, Tobacco, and Firearms, U.S. Department of the Treasury, for their assistance.