• Lemons are acidic.lemon image by Maria Brzostowska from Fotolia.com
  
  An acid is any substance that increases concentration of hydrogen ions in a solution. Acids have a pH level between one and six. The lower the pH, the more acidic, and potentially dangerous, the substance is. Several common household items are acidic, from foods to cleaning agents.
  
  

Food and Ingredients

• Lemon juice has a pH level between two and three; it is a citric acid. Lemon juice is a common cooking ingredient. Vinegar has a pH of around three; like lemon juice, it is used for cooking purposes. Both lemon juice and vinegar can also be used as household cleaning agents.
  
  

Household Cleaners

• Many common household cleaners are acidic, such as drain cleaners and rust removers, and even some chemicals used to clean pools. Sulfuric and phosphoric acid are found in some of these cleaners, making the liquid and the fumes dangerous.
  
  

Other Household Acidic Products

• Muriatic acid is used to clean bricks and stones; on patios for example. This acid is highly corrosive and has a very low pH: 1.2 on average. Sulfuric acid is a component in batteries; sulfuric acid in batteries has a pH of around .8.