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: Massive cerebral edema associated with fulminant hepatic failure in acetaminophen overdose : possible role of cranial decompression .
### Output Text:
Massive cerebral edema associated with fulminant hepatic failure in <span class="chemical">acetaminophen</span> overdose : possible role of cranial decompression . 