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: For the primary variable the difference was 0 . 5 mm Hg in favor of valsartan ( p = 0 . 68 ; 95 % confidence interval , - 2 . 7 to 1 . 7 ) .
### Output Text:
For the primary variable the difference was 0 . 5 mm Hg in favor of <span class="chemical">valsartan</span> ( p = 0 . 68 ; 95 % confidence interval , - 2 . 7 to 1 . 7 ) . 