White vinegar is a common solution of acetic acid at five-percent strength; pharmacies and photography shops offer a 10-percent solution. Vinegar is somewhat overrated as a universal cleaning agent since much house cleaning involves the removal of grease and greasy dirt, which are themselves acids best removed by neutralization with alkaline cleaners.
Vinegar also may be used to remove lime scale on plumbing fixtures — as long as you’re willing to be patient — and in appliances, such as coffee makers and humidifiers.
Soak scale-encrusted items for several hours in vinegar, then try to use a gentle abrasive pad or an old toothbrush to remove scale; continue soaking if any scale remains.
In appliances, add undiluted vinegar and turn on the appliance briefly to warm the acid, then shut it off and leave the appliance alone. After at least an hour, turn coffee makers back on to “brew” the acid-lime solution out of the machine; empty the solution out of humidifiers, brushing away any remaining scale. In both cases, run plenty of clean water through the appliance to rinse away remaining acid.
Full strength vinegar has also been cited as an effective germ-killer.
Reference:
William R. Griffin, Cleaning Consultant Services Inc., Seattle WA.
Vicki Lansky, Practical Parenting, Minnetonka MN.