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: In patients premedicated with scopolamine + morphine ( + 5 mg nitrazepam the evening before surgery ) , the sleep - inducing effect of midazolam 0 . 15 mg / kg i . v . was clearly slower in onset than that of thiopentone 4 . 67 mg / kg i . v . Somewhat fewer cardiovascular and local sequelae were found in the midazolam group , but , although apnoea occurred less often in the midazolam group it lasted longer .
### Output Text:
In patients premedicated with <span class="chemical">scopolamine</span> + <span class="chemical">morphine</span> ( + 5 mg <span class="chemical">nitrazepam</span> the evening before surgery ) , the sleep - inducing effect of <span class="chemical">midazolam</span> 0 . 15 mg / kg i . v . was clearly slower in onset than that of <span class="chemical">thiopentone</span> 4 . 67 mg / kg i . v . Somewhat fewer cardiovascular and local sequelae were found in the <span class="chemical">midazolam</span> group , but , although apnoea occurred less often in the <span class="chemical">midazolam</span> group it lasted longer . 