Lemon is a relatively weak citric acid that will remove some stains without damaging the item being cleaned. You can use lemon juice to clean any substance that you would otherwise clean with vinegar, such as glass, brass or copper. You can enhance the cleaning power of lemon juice by sprinkling salt over the material before rubbing it with half of a lemon. The salt will work as a mild abrasive to scrub away difficult stains, such as rust or sticker residue on glass.
Oranges are preferred over lemons by homeowners who want to deliver an orange scent to their cleaning products. Because oranges contain citric acid, they often enhance the power of the cleaning solution. Add a few drops of orange juice or peel to a solution to make it smell better. You can also put citrus peels down your garbage disposal to make it smell better and gently clean the grinding blades.
You can purchase citric acid powder at health food stores and use it to enhance the performance of your cleaning solutions. For example, add four teaspoons of citric acid to ¼ cup of white distilled vinegar and ¼ cup of grain alcohol to make a natural carpet cleaning shampoo rinse. Use the solution to rinse out the shampoo. The citric acid gives the carpet luster.