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: Maximum blood loss was greatest at the upper and lower dose levels , and lowest in the 70 - 125 microg dose range .
### Output Text:
Maximum blood loss was greatest at the upper and lower dose levels , and lowest in the 70 - 125 microg dose range . 