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: Disappearance of seizures and normalization of abnormal EEG with disappearance of seizures were recognized in 77 % and 50 % , respectively .
### Output Text:
Disappearance of seizures and normalization of abnormal EEG with disappearance of seizures were recognized in 77 % and 50 % , respectively . 