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: Acute liver failure in two patients with regular alcohol consumption ingesting paracetamol at therapeutic dosage .
### Output Text:
Acute liver failure in two patients with regular <span class="chemical">alcohol</span> consumption ingesting <span class="chemical">paracetamol</span> at therapeutic dosage . 