Spectrum discharge tubes contain gases that, when ignited, emit different waves of light (or the gas's spectral lines). These spectrum discharge tube is approximately 26cm  long approximately, central capillary portion approximately (90-100mm) long with electrodes sealed at both ends that are connected to lead wires protected by metal caps. Needs a suitable Spectrum discharge tube power supply as cat# PH0970. Spectrum tubes should only be used intermittently and are not intended as a continuous source of light. Spectrum - White with faint Violet. When students view the lighted tube through a spectroscope, they can observe the unique set of spectral lines for each gas. Recommended for use by adults only.