produces such compounds as CaCl2.4EtOH. Even some oxides (like BaO), which are insoluble in water without decomposition, dissolve. While ethanol can be toxic if ingested in large amounts, it is not considered as hazardous from this standpoint. For eight hour exposures, ethanol vapors should not exceed 1,000ppm (1.90 gram per cubic meter). Ethanol is utilized in a large number of aerosols. It is a VOC compound and often the limit is prescribed by the California Air Resources Board (CARB) and the U.S. Environmental Protection Agency (EPA) regulations. A brief listing of such formulations appears in Table 2, including typical amounts of ethanol. N.Propanol In past years, n.propanol has been made by the fermentation of molasses, sugar beets and other carbohydrates. Under ideal conditions, compositions such as 60% n.propanol, 30% acetone and small amounts of ethanol, carbon dioxide and hydrogen can be formed. The presently preferred process involves the hydrolysis of ethylene to mainly create ethanol, but also to generate small amounts of the byproduct fusel oil. This is a complex mixture that contains 3–% n.propanol, as well as a large amount of dl.2-methyl butyl alcohol, about 20% of iso.butyl alcohol, a minor amount of iso.amyl alcohol and traces of n.butyl alcohol and n.amyl alcohol. Higher alcohols are often present. Fusel oil has a disagreeable odor, a flash point of 91°F (32.7°C) and a boiling point of about 128°F (53.3°C). n.Propanol has an odor similar to that of iso.propanol. The flash point is 59°F (15°C) and its LEL is 2.15% in air. It is relatively more toxic than iso.propanol, with a maximum suggested 200ppm for eight-hour exposures. It is a VOC. n.Propanol was once used for many years as a de-icer in Prestone aerosol products. It is now used in some lacquers as a thinner and reportedly in an automotive bug remover. Its uses can almost always be duplicated by the cheaper and technically safer iso.propanol isomer. Iso.Propanol This is the second most important alcohol after ethanol. It is a significant portion of the product mix produced by the hydrolysis of propylene in catalyzed reactions at 500°F (260°C) temperatures and high pressures. It is readily separated from acetone by fractional distillation that produces the azeotrope of 88% isopropyl alcohol (IPA) and 12% water, boiling at 80.4°C (176.7°F). The water is generally removed by ternary distillation, yielding an extremely dry 99.9+% product. A 70% mixture of IPA with 30% water is sold as “rubbing alcohol” for skin applications. IPA is arguably the most flammable alcohol. Its LEL is 2.02% in air and it has a flash point of 53°F (11.6°C). For eight-hour exposures, the maximum suggested IPA level is 400ppm. It has a fairly strong, characteristic odor, less pleasing than that of ethanol, and this has limited its aerosol uses to some extent. It is not irritating to intact skin. The aerosol uses of iso.propanol include de-icers, insect repellants, automotive sprays, insecticides, paints and lacquers. Window cleaners and leather dressings usually contain around 5%. White nitrocellulose lacquers contain up to 12%. It is also found in art fixatives. See Table 3. N.Butanol Originally separated as a minor ingredient of fusel oil, this alcohol is now prepared by heating ethanol and barium ethylate under pressure. It is the most widely used of the four butyl alcohols. It is more toxic than the C2 and C3 alcohols, with an eight-hour suggested exposure maximum concentration of 100ppm in air. The flash point is 100°F (37.7°C) and the LEL is 1.71% in air. Its aerosol applications are limited to some paints and coatings. 40 Spray March 2017 Table 2. Ethanol in Aerosol Products Table 2. Ethanol in Aerosol Products Hair sprays 61% Hair lusterizing sprays 10% Hair Mousses to 2% Some de-icers to 60% Underarm deodorants to 10% Disinfectants/deodorants 66% Air fresheners (single phase) 30% Quick-breaking foam sanitizers 58% A few cook release sprays to 10% Table 3. Iso.Propanol compared with other solvents Methanol (39% in water) Freezes at -39°C (-38°F) Ethanol (60% in water) Freezes at -39°C (-38°F) Iso.Propanol (60% in water) Freezes at -23°C (-9°F) Iso.Propanol (80% in water) Freezes at -42°C (-44°F) Propylene Glycol (50% in water) Freezes at -33°C (-28°F)
Spray March 2017
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