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: During treatment , adverse cardiac effects were observed in 14 patients ( 18 % ) .
### Output Text:
During treatment , adverse cardiac effects were observed in 14 patients ( 18 % ) . 