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: The normal - sodium group showed an immediate but temporary rise of the renin and aldosterone levels ; in the low - sodium group renin and aldosterone increased more slowly but remained elevated .
### Output Text:
The normal - <span class="chemical">sodium</span> group showed an immediate but temporary rise of the renin and <span class="chemical">aldosterone</span> levels ; in the low - <span class="chemical">sodium</span> group renin and <span class="chemical">aldosterone</span> increased more slowly but remained elevated . 