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: Poisoning with yellow phosphorus classically manifests with acute hepatitis leading to acute liver failure which may need liver transplantation .
### Output Text:
Poisoning with yellow <span class="chemical">phosphorus</span> classically manifests with acute hepatitis leading to acute liver failure which may need liver transplantation . 