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 225 mg / m2 level was expanded for the phase II study since the highest level achieved ( 250 mg / m2 ) required modification because of nonhematologic toxicities ( arthralgia and sensory neuropathy ) .
### Output Text:
The 225 mg / m2 level was expanded for the phase II study since the highest level achieved ( 250 mg / m2 ) required modification because of nonhematologic toxicities ( arthralgia and sensory neuropathy ) . 