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: Hemolytic - uremic syndrome following quinine ingestion is a newly described phenomenon , with just two previous descriptions of 4 cases in the literature .
### Output Text:
Hemolytic - uremic syndrome following <span class="chemical">quinine</span> ingestion is a newly described phenomenon , with just two previous descriptions of 4 cases in the literature . 