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: Infusions of calcium chloride sufficient to raise serum calcium concentrations 2 mEq . per liter failed to increase calcium influx into the myocardial cell .
### Output Text:
Infusions of <span class="chemical">calcium chloride</span> sufficient to raise serum <span class="chemical">calcium</span> concentrations 2 mEq . per liter failed to increase <span class="chemical">calcium</span> influx into the myocardial cell . 