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: Pharmacological characteristics and side effects of a new galenic formulation of propofol without soyabean oil .
### Output Text:
Pharmacological characteristics and side effects of a new galenic formulation of <span class="chemical">propofol</span> without soyabean oil . 