This set of 6 premium Geissler tubes is designed to demonstrate the differing discharge characteristics of a gas discharge tube under varying degrees of vacuum. These large Geissler tubes measure approximately 16" / 40cm in length and 1" / 2.5cm in diameter. The cathode is disc shaped and the anode is pointed. All tubes are clearly identified with degree of vacuum in mm Hg and include the following:
40mm Hg Violet streamers appear between electrodes 10mm Hg A pink glow fills the tube, concentrated around the anode 3mm Hg Discharge becomes faint blue, Faraday's dark space appears 1mm Hg Faraday's dark space expands 0.10mm Hg Cathode begins to fluoresce 0.02mm Hg Cathode rays emerge, causing the tube sides to fluoresce
Both electrodes on these premium tubes have a full glass envelope. A plastic stand, insulated electrode and connecting wire with clip are included (as shown in product photo). A 50mm induction coil is the recommended power supply.
In the old days these were named vacuum cross scale. They are used for demonstration purposes to show what a discharge looks like at various vacuum levels.The tubes work well and seem to have the correct pressures. The stand is okay but I would like a way to connect the wire to the top of the tube. I am actually amazed they can sell a set like this for 100 bucks so I give it 5 stars based on cost/performance.