14524
As quantified by a molybdate assay , the length of the covalently tethered triple helix ( number of POG units ) determines the amount of amorphous silica obtained from silicic acid solution .
 Chemical: silica; Chemical: silicic acid
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: silica, silicic acid 
Answer:
 Chemical: silica; Chemical: silicic acid