sentence: Coal contains sulfur ions which are released when it burns.
sentences_before: Sulfur can be found in the earth near volcanoes. Many minerals contain sulfur ions.
sentences_after: Hydrogen sulfide and sulfur dioxide are some sulfur compounds that are released when coal burns. They are reacted to make sulfur.
concept_name: coal
headings: Sulfur Occurrence and preparation
categories: Chemical elements Nonmetals