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 stone passed spontaneously and was found to contain a triamterene metabolite admixed with uric acid salts .
### Output Text:
The stone passed spontaneously and was found to contain a <span class="chemical">triamterene</span> metabolite admixed with <span class="chemical">uric acid salts</span> . 