Citric acid is a natural and biodegradable substance that is found in citrus fruits. It is commonly used along side laundry soaps or detergents to boost cleaning power. Some laundry stripping recipes call for citric acid. It is also often used for descaling coffee machines, kettles, shower doors and the inside of washing machines and dishwashers. Please refer to your owners manual for instructions on using citric acid for descaling.