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: Mean urinary protein of patients who returned to dialysis was 1 . 26 ( 0 . 5 to 3 . 5 ) g / d before and 4 . 7 ( 3 to 12 ) g / d after conversion ( P = . 01 ) .
### Output Text:
Mean urinary protein of patients who returned to dialysis was 1 . 26 ( 0 . 5 to 3 . 5 ) g / d before and 4 . 7 ( 3 to 12 ) g / d after conversion ( P = . 01 ) . 