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: RESULTS : 272 cases of confusion were reported with valproic acid : 153 women and 119 men .
### Output Text:
RESULTS : 272 cases of confusion were reported with <span class="chemical">valproic acid</span> : 153 women and 119 men . 