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: Sublingual nitroglycerin ( 0 . 5 mg ) was administered .
### Output Text:
Sublingual <span class="chemical">nitroglycerin</span> ( 0 . 5 mg ) was administered . 