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: Forty - eight hours after admission , the children appeared to be at their baseline and were discharged home .
### Output Text:
Forty - eight hours after admission , the children appeared to be at their baseline and were discharged home . 