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: METHODS : Twenty - three dogs were randomized to receive either 1 ) three intravenous ( IV ) boluses of cocaine 7 . 5 mg / kg with ethanol ( 1 g / kg ) as an IV infusion ( C + E , n = 8 ) , 2 ) three cocaine boluses only ( C , n = 6 ) , 3 ) ethanol infusion only ( E , n = 5 ) , or 4 ) placebo boluses and infusion ( n = 4 ) .
### Output Text:
METHODS : Twenty - three dogs were randomized to receive either 1 ) three intravenous ( IV ) boluses of <span class="chemical">cocaine</span> 7 . 5 mg / kg with <span class="chemical">ethanol</span> ( 1 g / kg ) as an IV infusion ( C + E , n = 8 ) , 2 ) three <span class="chemical">cocaine</span> boluses only ( C , n = 6 ) , 3 ) <span class="chemical">ethanol</span> infusion only ( E , n = 5 ) , or 4 ) placebo boluses and infusion ( n = 4 ) . 