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: Tetany and rhabdomyolysis due to surreptitious furosemide - - importance of magnesium supplementation .
### Output Text:
Tetany and rhabdomyolysis due to surreptitious <span class="chemical">furosemide</span> - - importance of <span class="chemical">magnesium</span> supplementation . 