8, James DeWar mad a major advance when he succeeded in liquefying hydrogen at 20 K. The reason this advance was so spectacular was that hydrogen is also boiling at this temperature. This presented a very difficult handling and storage problem. DeWar solved this problem by inventing a double-walled storage container known as the DeWar flask. This flask could contain and hold the liquid hydrogen for a few days. However, at this time scientists realized that if they were going to make any more advances in this field of cryogenics, they would have to have better holding containers. Scientists then came up with insulation techniques that we still use today. These techniques include expanded foam materials and radiation shielding. (2) The last major advance in cryogenics finally came in 1908 when the Dutch physicist Heike Kamerling Onnes liquefied Helium at 4.2 and then 3.2 K. The rest of the advances in cryogenics have been extremely small since it is a fundamental Thermodynamic law that you can approach but never actually reach absolute zero. Since 1908 our technology has greatly increased and we can now freeze sodium gas to within 40 millionths of a Kelvin above absolute zero. However, in the back of every physicists head they want to break the Thermodynamic Law and reach a temperature of absolute zero where every proton, electron, and neutron in an atom is absolutely frozen. Also, there are two subjects that are also closely related to cryogenics called Superconductivity and Superfluity. Superconductivity is a low-temperature phenomenon where a metal loses all electrical resistance below a certain temperature, called the Critical Temperature (Tc), and transfers to a state of zero resistance. (3) Heike Kamerlingh Onnes also discovered this unusual behavior. This Critical Temperature was discovered when Onnes and one of his graduate students realized that Mercury loses all of its electrical resistance when it reaches a temperature...
