Ultra Pure Citric Acid Citric Acid is a multi-purpose household product. It is a food grade product and can be used as an additive in cooking to give a "sour" flavour or in producing fizzy drinks or sodas. It is excellent for descaling kettles and easy to use – just add a teaspoon to a full kettle of water, boil, discard the contents and rinse thoroughly. Citric Acid also works very well as a descaler around the house, on taps, sinks and baths for example. Always rinse well after use. 50g