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: Four types of experimental arrhythmia are used - - with BaCl2 , with chloroform - adrenaline , with strophantine G and with aconitine .
### Output Text:
Four types of experimental arrhythmia are used - - with <span class="chemical">BaCl2</span> , with <span class="chemical">chloroform</span> - <span class="chemical">adrenaline</span> , with <span class="chemical">strophantine G</span> and with <span class="chemical">aconitine</span> . 