Boric acid is often used to kill insects and has many other industrial uses. it is a weak acid that often comes in an odorless colorless powder, which can be dissolved in water. boric acid was first discovered over 400 years ago by wilhelm homberg, who was able to extract boric acid from a type of salt called borax. Nov 28, 2018u00a0u00b7 dissolve boric acid powder in warm water to make your own weedkiller spray. put on protective gloves. mix 10 ounces of boric acid powder into 1/2 cup of warm water, and stir the mixture until all ... Boric acid is commonly used around the house to solve various cleaning and pest control problems. most commonly sold as a powder, boric acid easily dissolves in water to form a liquid spray. boric acid is much less toxic that most commercial cleaners and can be used for pest control, cleaning, removing mildew and weed control.