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: Haloperidol failed to prevent amphetamine - induced seizures , but did lower the mortality rate at most doses tested .
### Output Text:
<span class="chemical">Haloperidol</span> failed to prevent <span class="chemical">amphetamine</span> - induced seizures , but did lower the mortality rate at most doses tested . 