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: Fifty - four patients , aged 27 - 90 years , who were given lignocaine 5 % in 6 . 8 % glucose solution for spinal anaesthesia were studied .
### Output Text:
Fifty - four patients , aged 27 - 90 years , who were given <span class="chemical">lignocaine</span> 5 % in 6 . 8 % <span class="chemical">glucose</span> solution for spinal anaesthesia were studied . 