Durham tubes are inverted (top of tube facing the bottom of the test tube) such that the tubes are closed at the top and open at the bottom. When gas is produced in these media a. small bubble representing trapped gas. can be found in the tube.
A compound is a substance formed when two or more chemical elements are chemically bonded together. Two types of chemical bonds common in compounds are covalent bonds and ionic bonds.The elements in any compound are always present in fixed ratios.xample 1: Pure water is a compound made from two elements-hydrogen and oxygen. The ratio of hydrogen to oxygen in water is always 2:1. Each molecule of water contains two hydrogen atoms bonded to a single oxygen atom. Example 2: Pure table salt is a compound made from two elements-sodium and chlorine.
1.1 (also chemical compound) A substance formed from two or more elements chemically united in fixed proportions: a compound of hydrogen and oxygen lead compounds. More example sentences. 1  The layers of plants and animals slowly broke down into simple substances called hydrocarbons, compounds of hydrogen and carbon..1 (also chemical compound) A substance formed from two or more elements chemically united in fixed proportions: a compound of hydrogen and oxygen lead compounds. More example sentences. 1  The layers of plants and animals slowly broke down into simple substances called hydrocarbons, compounds of hydrogen and carbon.