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: Beneficial effect of oral galactose was independent of the rat age and of the galactose dose ranging from 100 to 300 mg / kg / day .
### Output Text:
Beneficial effect of oral <span class="chemical">galactose</span> was independent of the rat age and of the <span class="chemical">galactose</span> dose ranging from 100 to 300 mg / kg / day . 