To clean dry cat urine out of carpet, mix equal amounts of water and white vinegar in a spray bottle and apply the mixture to the urine stain on the carpet. Allow the solution to settle into the carpet for approximately 30 minutes. Blot the stain with dry, clean towels until the liquid is completely absorbed.
Sprinkling a thin layer of baking soda on the stain can also remove dry cat urine from carpet. Allow the baking soda to settle into the carpet, and then spray a mixture of 1/4 cup of 3 percent hydrogen peroxide and 1 teaspoon of liquid dish soap on top of the baking soda.
Use a stiff brush to push the mixture deep into the carpet, scrubbing until the mixture dissolves into the stain. The mixture takes a few hours to dry; vacuum the remaining powder once the area is dry.
If you're concerned about discoloring the affected area of the carpet, first test a small area of the carpet in a hidden corner with the mixtures first and let it dry to see the effect. A thorough steam cleaning of the entire carpet area can help to even up the color of the carpet.