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: In an attempt to determine whether penile pain associated with intracorporeal injections could be due to the acidity of the medication , we performed a randomized study comparing the incidence of penile pain following intracorporeal injections with or without the addition of sodium bicarbonate to the intracorporeal medications .
### Output Text:
In an attempt to determine whether penile pain associated with intracorporeal injections could be due to the acidity of the medication , we performed a randomized study comparing the incidence of penile pain following intracorporeal injections with or without the addition of <span class="chemical">sodium bicarbonate</span> to the intracorporeal medications . 