How do I Convert 91% Rubbing Alcohol to 70% Rubbing Alcohol?

A solution contains a solute, like salt, dissolved in a solvent, like water.

Rubbing alcohol is a solution of isopropyl alcohol in water. Ninety-one percent rubbing alcohol contains 91 percent isopropyl alcohol as measured by volume and is useful for a wide variety of tasks and chores around the home, including first aid, cleaning and disinfecting surfaces. In general, it's not necessary to dilute 91 percent rubbing alcohol before using it, but if you need a weaker solution of rubbing alcohol to clean a particular item, follow the steps outlined below.

Things You'll Need

• Water
• Plastic container
• Measuring cup
• 91 percent rubbing alcohol
• Spoon

Instructions

1. Measure out one cup of 91 percent rubbing alcohol, and pour it into the plastic container.

2. Add one-third of a cup of water and stir to mix the solution. The solution is now 70 percent rubbing alcohol.

3. Repeat this procedure as often as needed to obtain the desired amount of 70 percent rubbing alcohol.

Tips & Warnings

• You can use any amount of rubbing alcohol you like as long as the combined volume of the water you add and the 91 percent rubbing alcohol is equal to 1.3 times the volume of the 91 percent rubbing alcohol alone.

• Do not drink or ingest rubbing alcohol or any kind of isopropyl alcohol, no matter how dilute the solution. According to the JT Baker material safety data sheet, the lethal dose of isopropyl alcohol for an adult human can be as little as eight oz. If you think you have inadvertently ingested isopropyl alcohol, seek medical attention immediately.

References

• "Chemical Principles, the Quest for Insight, 4th Edition"; Peter Atkins and Loretta Jones; 2008.
• Reader's Digest: Thirteen Ways to Use Rubbing Alcohol
• Centers for Disease Control and Prevention: Isopropy Alcohol
• JT Baker MSDS: Isopropyl Alcohol