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Eventually it was discovered that metallic zinc could be alloyed with copper to make brass , a process known as speltering , and by 1657 the German chemist Johann Glauber had recognised that calamine was " nothing else but unmeltable zinc " and that zinc was a " half ripe metal .
 Johann Glauber
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: location, person, organization 
Text: {0} 
Answer:
 Johann Glauber