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: Chronic oral administration of propranolol ( 40 - 160 mg / day ) also elevated the blood pressures of these individuals with increases in the order of 20 - 35 / 15 - 25 mmg being observed .
### Output Text:
Chronic oral administration of <span class="chemical">propranolol</span> ( 40 - 160 mg / day ) also elevated the blood pressures of these individuals with increases in the order of 20 - 35 / 15 - 25 mmg being observed . 