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: There were more deaths in the mexiletine group ( 7 . 6 % ) than in the placebo group ( 4 . 8 % ) ; the difference was not statistically significant .
### Output Text:
There were more deaths in the <span class="chemical">mexiletine</span> group ( 7 . 6 % ) than in the placebo group ( 4 . 8 % ) ; the difference was not statistically significant . 