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: Lower doses ( 3 and 10mg / kg ) did not suppress seizures , however , after administration of 10mg / kg , significant reductions in seizures duration ( 24 . 3 + / - 6 . 8s ) and seizure number ( 1 . 6 + / - 0 . 34 ) were found .
### Output Text:
Lower doses ( 3 and 10mg / kg ) did not suppress seizures , however , after administration of 10mg / kg , significant reductions in seizures duration ( 24 . 3 + / - 6 . 8s ) and seizure number ( 1 . 6 + / - 0 . 34 ) were found . 