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: A significant decrease in the baseline excretion rate of uric acid was found in rats given suprofen , compared with drug - free controls .
### Output Text:
A significant decrease in the baseline excretion rate of <span class="chemical">uric acid</span> was found in rats given <span class="chemical">suprofen</span> , compared with drug - free controls . 