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: We studied a patient with no prior history of neuromuscular disease who became virtually quadriplegic after parenteral magnesium administration for preeclampsia .
### Output Text:
We studied a patient with no prior history of neuromuscular disease who became virtually quadriplegic after parenteral <span class="chemical">magnesium</span> administration for preeclampsia . 