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 CD50 and LD50 , respectively , were 57 . 7 and 58 . 7 mg / kg for bupivacaine , 111 . 0 and 133 . 1 mg / kg for lidocaine , and 243 . 4 and 266 . 5 mg / kg for chloroprocaine .
### Output Text:
The CD50 and LD50 , respectively , were 57 . 7 and 58 . 7 mg / kg for <span class="chemical">bupivacaine</span> , 111 . 0 and 133 . 1 mg / kg for <span class="chemical">lidocaine</span> , and 243 . 4 and 266 . 5 mg / kg for <span class="chemical">chloroprocaine</span> . 