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: Flunitrazepam 0 . 5 , 1 . 0 or 2 . 0 mg was given by the oral or i . m . routes to groups of volunteers and its effects compared .
### Output Text:
<span class="chemical">Flunitrazepam</span> 0 . 5 , 1 . 0 or 2 . 0 mg was given by the oral or i . m . routes to groups of volunteers and its effects compared . 