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: Two minutes after remifentanil or placebo injection , etomidate 0 . 3 mg / kg was given .
### Output Text:
Two minutes after <span class="chemical">remifentanil</span> or placebo injection , <span class="chemical">etomidate</span> 0 . 3 mg / kg was given . 