Complexometric titrations are titrations that can be used to discover the hardness of water or to discover metal ions in a solution. Ethylenediaminetetraacetic acid, also known as EDTA, is commonly used in complexometric titrations. This is because it makes six bonds with metal ions to form one to one complex (“Complex Titrations”). In a complexometric titration, an ion is transformed into a complex ion. The equivalence point is determined by a metal indicator. Erichrome black T is an indicator that can be used to determine calcium content in a solution. The complex that is initially formed is red. After all the calcium ions have reacted, the complex then turns blue. This indicates the endpoint of the titration