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 total doses of ACC - 9653 or phenytoin sodium necessary to convert the arrhythmia to a normal sinus rhythm were 24 + / - 6 and 14 + / - 3 mg / kg , respectively .
### Output Text:
The total doses of <span class="chemical">ACC - 9653</span> or <span class="chemical">phenytoin sodium</span> necessary to convert the arrhythmia to a normal sinus rhythm were 24 + / - 6 and 14 + / - 3 mg / kg , respectively . 