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 single - blind parenteral challenge with Triniol was positive in both patients after the administration of 1 ml of the drug , and negative with its excipients .
### Output Text:
A single - blind parenteral challenge with Triniol was positive in both patients after the administration of 1 ml of the drug , and negative with its excipients . 