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: Two days before admission diltiazem ( 60 mg b . i . d . ) was prescribed in addition .
### Output Text:
Two days before admission <span class="chemical">diltiazem</span> ( 60 mg b . i . d . ) was prescribed in addition . 