A double indicator titration is the process used in chemistry experiments to determine and analyze the amount and concentration of acids or bases in a solution at two end points. For example, when titrating sodium carbonate, hydrocholoric acid is added to form sodium hydroxide, the first endpoint, and then hydrochloric acid is added again to form carbonic acid, the second endpoint.
The process of titration includes an analyte, which is a substance that is being analyzed; an indicator, such as methyl orange or phenolphthalein, which changes the color of the endpoints to reflect the change; and a titrate, which is the substance of known acidity being added to the analyte. Reference points out that titrations are used not only to determine the concentration of acids or bases in a solution, but to determine the number of those acids in relation to bases as well. Sometimes an indicator can be replaced by graph plotting. In this process, the pH of the solution is plotted regularly as well as the amount of added nitrate.
Titrating solutions were introduced in the 1700s in France when Francois-Antoine-Henri Descroizilles first developed the burette or graduated cylinder, which is used when volumes of a liquid or titrates are added to a solution. It was improved upon in 1824 by Joseph Louis Gay-Lussac and then by Karl Friedrich Mohr in 1855.