23400
However , in its free form copper can participate in Fenton - like reactions that produce reactive hydroxyl radicals .
 Chemical: copper; Chemical: hydroxyl
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: copper, hydroxyl 
Answer:
 Chemical: copper; Chemical: hydroxyl