In this task, you are given a question and answer options for that question. Using this information, you have to classify each text into different topics: medicine, nursery, psychology, chemistry, pharmacology, biology.

Question: Ethylenediaminetetraacetic acid (EDTA) is a chelating agent widely used as a titrator in complexometric assessments that are characterized by: 
 Options:  <0> To make possible the EDTA titration of many metals in alkaline solutions an auxiliary complexing agent is used which prevents the metal ion from precipitating as hydroxide. <1> EDTA forms complexes of 1: 2 stoichiometry with some metal ions and therefore has a poor application in quantitative analysis. <2> It is important to choose an adequate pH to carry out the titration because metal-EDTA complexes are more stable at low pH than at high pH. <3> When evaluating a metal ion with EDTA, there is an excess of EDTA at the equivalence point. <4> When evaluating a metal ion with EDTA, there is an excess of metallic ion at the equivalence point.
pharmacology