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: Antipsychotic - like profile of thioperamide , a selective H3 - receptor antagonist in mice .
### Output Text:
Antipsychotic - like profile of <span class="chemical">thioperamide</span> , a selective H3 - receptor antagonist in mice . 