14855
The ratio of AMPS to AA groups was varied to balance the requirement of colloid dispersibility at high salinity ( provided by AMPS ) against the need for anchoring of the polymers to the iron oxide surface ( via the AA ) .
 Chemical: AMPS; Chemical: AMPS; Chemical: iron oxide
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: AMPS, AMPS, iron oxide 
Answer:
 Chemical: AMPS; Chemical: AMPS; Chemical: iron oxide