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Among the surface treatments tested for the glass vials , sulfur treatment showed a protective effect on the particle formation in the vials , whereas the SiO2 coating did not have any protective effects .
 Chemical: sulfur; Chemical: SiO2
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: sulfur; Chemical: SiO2