Lab grade ammonia water is 28%. I believe household ammonia water is more like 10% though the bottle I am looking at doesn't give a percentage; just says "Pure Ammonia". As Mystic said, the houshold grade stuff works fine, look for clear, non-sudsy, pure ammonia in your household cleaning section.
You can make beautiful, large, snowflake crystals of cocaine hydrochloride with acetone, methanol and conc. hydrochloric acid. I believe that I have posted the procedure here, I will use the search engine to see if I can find it. The procedure is from a book Cocaine Handbook; An Essential Reference by David Lee, publ And/Or Press, 1981. Unfortunately this book is probably out of print - it has some great photos of "snowstorms" in beakers of acetone.
Back in the 70's and early 80's, before crack, people would prepare their own cocaine freebase for smoking using ammonia water and extracting the freebase with low boiling point petroleum ether. In some neighborhoods in So. Cal. you could buy kits in liquor stores containing a vial (for dissolving the cocaine HCl in water and performing the conversion), a medicine dropper and a small bottle each of ammonia water and petroleum ether. It was petroleum ether with which Richard Prior caught himself on fire.
The procedure was to dissolve the cocaine HCl in water in the vial and add the ammonia water. The cocaine freebase would float to the top, usually as an oil at first. As an aid to getting all the freebase out a little pet. ether would be added and the vial capped and inverted a few times. The eyedropper was then used to remove the freebase dissolved in the pet. ether and this placed on a plate so the pet. ether could evaporate. As the pet. ether evaporated and with a little scraping, the freebase would solidify and could be scraped up with a razor blade.