I have a 1 quart sealed bottle of 100% isopropyl alcohol that is 3 months expired. What is the safest way to dispose of this? I live in a small apartment in NYC and they have suspended waste drop off until the fall. I read that in addition to being highly flammable it could form peroxides and possibly explode so I definitely don't want to keep it around until then. Thanks for your help.
The best solution is probably to make a homemade room deodorizer or cleaner with the expired isopropanol.
In a well ventilated area mix 1:4 rubbing alcohol to water, add your favorite essential oils or extracts - almond or vanilla extract work well too, mint, lavender, and other essential oils are available at the grocery store (or online). The water does not have to be distilled - you can use filtered water from your refrigerator or tap water. You can even mix the same ratio in a small spray bottle - they are available in the travel section of your local grocery store (next to travel shampoo, deodorant, and toothpaste).
You can also make cleaner out of it.
Note the main reason 99% rubbing alcohol expires is because it is hygroscopic (sucks up water) and no matter how well you keep it, it will be diluted by water (humidity) when stored.
Last and worst option: If you don't want to make homemade air freshener or cleaner and are unable to turn it in to a household waste site, isopropyl alcohol may be diluted and disposed of in a sink in many areas. Check with your local utility provider and/or local regulations.
If it is safe in your area, in a well ventilated area dilute the isopropyl alcohol to less than 5% and poor it down the drain with running water.