Had weeds coming up thru my mulch border; I had used regular vinegar before, and it worked fine, but weeds soon returned. I couldn't wait to see what 75% vinegar would do.
I got a 2 gallon sprayer, and added about 2 cups of salt crystals used for water softeners to the bottom of the container. I filled the container about 2/3rds with hot water, added the entire bottle of 75% vinegar, then topped it off the rest of the way with more hot water, and two long squirts of Dawn dishwashing soap. It was close to 90 degrees out when I began spraying; it took about 20-25 minutes to spray the entire length of the mulch, and by the time I got to the end, those weeds that I sprayed in the beginning were completely wilted. I simply sprays the leaves very well, and moved on. My intent was to pull away the mulch, put down an additional barrier, and cover that with the mulch. I waited about an hour, and when I raked the mulch away, the weeds were not only completely dead by now, but the roots came out of the ground when raked away with the mulch. It works so well, I'll be ordering more to tame my fence line!
Tips: I have used regular table salt before to kill weeds, but these salt crystals work much better.
Make sure it's hot outside and that rain is not forecast for at least a day after you apply.
Hot water not only helps to dissolve the salt, but also promotes the killing of the weeds.
Do not spray or allow overspray on any grass or plants you want to keep; this stuff is unforgiving when it comes to killing plantlife
They mention its strong odor, and the need for ventilation, gloves, a face mask and protective clothing, but I think they are referring to indoor, household cleaning usage; although I was careful, outdoors, for weed killing, I didn't notice an overpowering odor or feel like I needed a mask or any special protective gear because the long-handled sprayer applied the mixture directly on the weeds.
Highly recommended for weed killing - when properly used. works great!
WARNING: 
