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: Dexamethasone was started between the 7th and the 28th day of life over 7 days with a total dose of 2 . 35 mg / kg / day .
### Output Text:
<span class="chemical">Dexamethasone</span> was started between the 7th and the 28th day of life over 7 days with a total dose of 2 . 35 mg / kg / day . 