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: Of 24 evaluable patients , two achieved a complete remission and one achieved a partial remission for an overall response rate of 12 . 5 % ( 95 % confidence interval : 2 . 6 - 32 . 4 % ) .
### Output Text:
Of 24 evaluable patients , two achieved a complete remission and one achieved a partial remission for an overall response rate of 12 . 5 % ( 95 % confidence interval : 2 . 6 - 32 . 4 % ) . 