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. 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 titrationIn the experiment, EDTA will first be made and then standardized. This will be done by preparing a calcium chloride solution. In the reaction with the EDTA, calcium carbonate is converted to calcium chloride. Ammonia-ammonium chloride will also be prepared to be used as a buffer in the solution. The professor prepared the Erichrome black T to be used as an indicator. This indicator will be cause the solution to be red at the before the titration and then at the endpoint, the solution will turn blue. Make sure it is blue and not purple. After the standardization of EDTA, the calcium content in an unknown water sample will be found. This will be done with same way as the first titration occurred. The hardness will then be calculated in parts per million.