Isopropyl alcohol is a small, carbon-based molecule in the same chemical family as ethanol, the alcohol in wine and beer. Unlike ethanol, however, isopropyl alcohol is not appropriate for internal consumption, but is instead used primarily as a solvent. It is fairly non-toxic to the skin, but the vapors can be irritating to respiratory tissue and mucous membranes. A very common and widely available chemical, isopropyl alcohol has a number of industrial and household uses.
Industrial and Household Cleaning
Isopropyl alcohol, or more commonly called "rubbing alcohol," is an excellent solvent for a variety of compounds and mixtures, including many oils, according to the Material Safety Data Sheet. Because it's quite stable and not particularly chemically reactive, isopropyl alcohol makes an effective household cleaner and can be used to remove grease and oil from electronic devices and the optical surfaces of CDs and DVDs. The Occupational Safety and Health (OSHA) guidelines for isopropyl alcohol further indicate that it's used in defogging solutions and windshield cleaners.
Chemical Synthesis and Purification
Isopropyl alcohol is not a highly reactive molecule, but it is useful in many biochemistry lab procedures, per OSHA guidelines. For instance, biochemists interested in removing the genetic material DNA from cells for study purposes face difficulty because the DNA is localized in a cell's nucleus and is quite difficult to remove. Isopropyl alcohol is helpful in removing the DNA and clustering it into bunches. In fact, this procedure is so technically simple that it's commonly done in high school and even middle school science labs; chopped-up onions are soaked in soapy water to destroy cell membranes, and then the DNA, which looks like a series of small white strings, is collected with isopropyl alcohol.
Personal Care
The Medical College of Wisconsin provides guidelines for using isopropyl alcohol as a desiccant, with applications to the treatment of swimmer's ear (see Resources). Swimmer's ear is an inflammation of the external ear canal that produces symptoms including pain and itching due to bacterial infection. Because bacteria responsible for the infection thrive in a chronically damp environment, drying the external ear canal relieves symptoms. If isopropyl alcohol is poured into the ear and then allowed to drip out, it mixes with water in the ear canal. The mixture of alcohol and water is far more volatile, meaning it evaporates with greater ease, than water alone, pulling water out of the ear and leaving it clean and dry.
Coolant Applications
The OSHA guidelines for isopropyl alcohol indicate that its low boiling point makes it a good coolant in both industrial and health care settings. Beer manufacturers, for instance, can use isopropyl alcohol in vaporization-condensation-style closed-loop cooling systems, which are very similar to those found in a home refrigerator. Evaporation of liquid is a very endothermic process, meaning that it requires heat. This is the principle behind sweating--the secretion of liquid onto the surface of the skin and subsequent evaporation of that liquid absorbs heat, which cools the body. Isopropyl alcohol evaporates at a lower temperature than water, making it an ideal "artificial sweat" for feverish patients--it is sponged onto large areas of skin such as the chest, and it decreases core temperature of the patient as it evaporates.
References
- "Material Safety Data Sheets"; Isopropyl Alcohol; Rev. 2009
- OSHA: Isopropyl Alcohol Guidelines
