In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: From January 1986 to January 2009 , 1223 consecutive ALF patients were evaluated : ATT alone was the cause in 70 ( 5 . 7 % ) patients .
### Output Text:
From January 1986 to January 2009 , 1223 consecutive ALF patients were evaluated : ATT alone was the cause in 70 ( 5 . 7 % ) patients . 