6973
The colloidal formulations were stable at pH 7 . 4 for several hours , while at pH 6 . 5 , they rapidly rearranged and aggregated .
 None
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:  
Answer:
 None