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 this group there were 1 complete and 5 partial remissions ( total 24 % ) , but nearly all patients developed either gross haematuria and / or symptoms of bladder irritation ( cystitis and pollakisuria ) .
### Output Text:
In this group there were 1 complete and 5 partial remissions ( total 24 % ) , but nearly all patients developed either gross haematuria and / or symptoms of bladder irritation ( cystitis and pollakisuria ) . 