27418
Its T1 Cu potential ranges between 471 and 318 mV versus the normal hydrogen electrode , at pH 5 . 5 and 8 , respectively ; this value is dependent both on the solution pH and electrode modification .
 Chemical: Cu; Chemical: hydrogen
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: Cu, hydrogen 
Answer:
 Chemical: Cu; Chemical: hydrogen