is sulfur a pure substance
Sulfur and iron: since this is a mixture, the sulfur retains its properties (its yellow color, for example), and the iron retains its properties (its black color, for example). These properties can be used to separate the two elements. For iron sulfide, two elements (sulfur and iron) are heated together so that they form the compound iron sulfide. Although iron sulfide contains both sulfur and iron, it is not a mixture: it is a pure substance. Both the sulfur and the iron have âgiven upâ their individual properties to become a compound.