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 ED50 doses were 16 mg / kg for i . v . ACC - 9653 and 8 mg / kg for i . v . phenytoin sodium .
### Output Text:
The ED50 doses were 16 mg / kg for i . v . <span class="chemical">ACC - 9653</span> and 8 mg / kg for i . v . <span class="chemical">phenytoin sodium</span> . 