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: Eight of the isolated - HIT patients developed thrombosis within the next 30 d ; thus , a total of 48 patients had thrombosis at day 30 .
### Output Text:
Eight of the isolated - HIT patients developed thrombosis within the next 30 d ; thus , a total of 48 patients had thrombosis at day 30 . 