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: About 62 % of the out - patients developed scoline pain as compared with about 26 % among the in - patients .
### Output Text:
About 62 % of the out - patients developed <span class="chemical">scoline</span> pain as compared with about 26 % among the in - patients . 