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: The results warrant clinical trials of denopamine in the treatment of cardiac failure .
### Output Text:
The results warrant clinical trials of <span class="chemical">denopamine</span> in the treatment of cardiac failure . 