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: Suxamethonium chloride ( Sch ) was administered i . v . to 36 adult males at six rates : 0 . 25 mg s - 1 to 20 mg s - 1 .
### Output Text:
<span class="chemical">Suxamethonium chloride</span> ( <span class="chemical">Sch</span> ) was administered i . v . to 36 adult males at six rates : 0 . 25 mg s - 1 to 20 mg s - 1 . 