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: The risk of renal papillary necrosis was increased nearly 20 - fold by consumption of phenacetin , which also increased the risk for cancer of the renal pelvis and bladder but not for ureteric cancer .
### Output Text:
The risk of renal papillary necrosis was increased nearly 20 - fold by consumption of <span class="chemical">phenacetin</span> , which also increased the risk for cancer of the renal pelvis and bladder but not for ureteric cancer . 