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 second group administered ZnSO ( 4 ) ( 0 . 1 micromol / 10 microl normal saline , i . c . v , once ) then BCNU solvent ( i . v ) after 24 h .
### Output Text:
The second group administered <span class="chemical">ZnSO ( 4 )</span> ( 0 . 1 micromol / 10 microl normal saline , i . c . v , once ) then <span class="chemical">BCNU</span> solvent ( i . v ) after 24 h . 