Vinegar, ketchup, citrus fruits, drain cleaners and milk are all household items that contain acids. Vinegar and ketchup contain acetic acid, citrus fruits contain citric and ascorbic acids, and milk and other dairy products contain lactic acid. Sulfuric acid is found in car batteries and some drain cleaners.
The pH scale indicates the acidity of a substance. Water is considered neutral at 7.0, lower pH is considered acidic, and higher pH is considered basic or alkaline. Acids are normally sour or bitter, and help remove difficult stains, such as rust or mineral deposits. Toilet bowl cleaners, tub and tile cleaners, and mold removers commonly have an acidic pH. A pH balanced rust remover has a pH low enough to remove rust, but high enough not to remove the enamel of a bathtub.
Cleaners that have a basic pH break down fatty and oily soils into components that are easier to remove. Oven cleaners, all-purpose cleaners and laundry detergents are common basic cleaning products. The average bottle of hand soap has a pH of 9, while bleach has a pH of 12.5, making it a strong disinfectant.
Baking soda and vinegar is touted as a magical cleaning combination. The agents must be used separately, as they react when combined, leaving mostly water and some sodium acetate. The resulting solution is an ineffective cleaner.