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: The overall reporting rate was estimated to be 1 . 3 / 100 , 000 treated patients .
### Output Text:
The overall reporting rate was estimated to be 1 . 3 / 100 , 000 treated patients . 