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 long P - P intervals ranged between 1 . 04 - 1 . 12 s and the short P - P intervals between 0 . 80 - 0 . 84 s , respectively .
### Output Text:
The long P - P intervals ranged between 1 . 04 - 1 . 12 s and the short P - P intervals between 0 . 80 - 0 . 84 s , respectively . 