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 recommend that hyperbaric lignocaine should be administered in concentrations not greater than 2 % and at a total dose preferably not exceeding 60 mg .
### Output Text:
We recommend that hyperbaric <span class="chemical">lignocaine</span> should be administered in concentrations not greater than 2 % and at a total dose preferably not exceeding 60 mg . 