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: A case of metabolic acidosis , acute renal failure and hepatic failure following paracetamol ingestion is presented .
### Output Text:
A case of metabolic acidosis , acute renal failure and hepatic failure following <span class="chemical">paracetamol</span> ingestion is presented . 