The crossword solution for the term CONTAINING ELEMENT #5 is BORIC, which is a five-letter word. Boric acid, also known as hydrogen borate, is an organic compound with the formula H3BO3. It is a weak, monobasic Lewis acid of boron, which is often used as an antiseptic, insecticide, flame retardant, and neutron absorber. Boric acid is also used in nuclear power plants to control the rate of fission.