Forms of Carbon In 1772 Lavoisier and other chemists bought a diamond and placed it in a closed glass jar . They used a remarkable giant magnifying glass to focus the sun ’ s rays on the diamond . The diamond burned and disappeared . Lavoisier noted the overall weight of the jar was unchanged , even though all of the diamond had disappeared . This observation would later be part of the evidence convincing him that his law of mass conservation was correct . Whether diamond or charcoal were burned by the giant lens , the same gas was produced – we now call it carbon dioxide . Lavoisier realized that diamond and charcoal are different forms of the same element . He gave this element the name carbon .
Oxygen and Combustion In 1772 people did not understand the process of burning . We now know that combustion happens when substances react with oxygen at high temperatures . In 1772 , however , when Lavoisier began working in this field , oxygen ’ s discovery by Joseph Priestley still lay two years in the future . In 1772 Lavoisier discovered that when phosphorus or sulfur are burned in air the products are acidic . The products also weigh more than the original phosphorus or sulfur , suggesting the elements combine with something in the air to produce acids . But what ? In 1779 Lavoisier coined the name oxygen for the element released by mercury oxide . He found oxygen made up 20 percent of air and was vital for combustion and respiration . He also concluded that when phosphorus or sulfur are burned in air , the products are formed by the reaction of these elements with oxygen .