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Zosimos ( circa 300 AD ) describes roasting " sandarach " ( realgar ) to obtain " cloud of arsenic " ( arsenic trioxide ) , which he then reduces to gray arsenic .
 Zosimos
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Zosimos