Simplify the following text for a Grade 12 native English-speaking person.
Original: For example , the water-soluble and very basic thallium ( I ) hydroxide reacts with carbon dioxide forming water-soluble thallium carbonate This carbonate is the only water soluble heavy metal carbonate .
Simplified: This reacts with carbon dioxide to make thallium ( I ) carbonate , which is also water-soluble and very heavy .