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: Among the 32 episodes , 26 ( 81 % ) had various degrees of azotemia , 18 ( 56 % ) occurred during bacterial infections and 14 ( 44 % ) without infection occurred during periods of dehydration .
### Output Text:
Among the 32 episodes , 26 ( 81 % ) had various degrees of azotemia , 18 ( 56 % ) occurred during bacterial infections and 14 ( 44 % ) without infection occurred during periods of dehydration . 