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: Argatroban 0 . 5 - 1 . 2 microg / kg / min typically supports therapeutic aPTTs .
### Output Text:
<span class="chemical">Argatroban</span> 0 . 5 - 1 . 2 microg / kg / min typically supports therapeutic aPTTs . 