21198
In BC preparations , Bbil - TX ( 0 . 5 - 10 mu g / ml ) caused time - and concentration - dependent blockade that was not reversed by washing ; the times for 50 % blockade were 87 +/- 7 , 41 +/- 7 and 19 +/- 2 min ( mean +/- SEM ; n = 4 - 6 ) for 1 , 5 and 10 mu g / ml , respectively .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 None