Helium, inert gas of Group 18 of the periodic table the second lightest element (only hydrogen is lighter), helium is a colorless, odorless, and tasteless gas that becomes liquid at −268.9 °C (−452 °F). The boiling and freezing points of helium are lower than those of any other known substance. Helium is the only element that cannot be solidified by sufficient cooling at normal atmospheric pressure; it is necessary to apply pressure of 25 atmospheres at a temperature of 1 K (−272 °C, or −458 °F) to convert it to its solid form. About 11.3 percent of all atoms in the universe are helium atoms. By comparison, about 88.6 percent of all atoms in the universe are hydrogen. Thus, at least 99.9 percent of all atoms are either hydrogen or helium atoms.
|Figure 1: Helium diagram|
By contrast, helium is much less abundant on Earth. It is the sixth most abundant gas in the atmosphere after nitrogen, oxygen, argon, carbon dioxide, and neon. It makes up about 0.000524 percent of the air. It is probably impossible to estimate the amount of helium in the Earth’s crust. The gas is produced when uranium and other radioactive elements break down. But it often escapes into the atmosphere almost immediately.  , 
Helium was discovered in the gaseous atmosphere surrounding the sun by the French astronomer Pierre Janssen, who detected a bright yellow line in the spectrum of the solar chromosphere during an eclipse in 1868; this line was initially assumed to represent the element sodium. That same year the English astronomer Joseph Norman Lockyer observed a yellow line in the solar spectrum that did not correspond to the known D1 and D2 lines of sodium, and so he named it the D3 line. Lockyer concluded that the D3 line was caused by an element in the Sun that was unknown on Earth; he and the chemist Edward Frankland used the Greek word for sun, Helios, in naming the element. The British chemist Sir William Ramsay discovered the existence of helium on Earth in 1895. Ramsay obtained a sample of the Uranium -bearing mineral cleveite, and, upon investigating the gas produced by heating the sample, he found that a unique bright yellow line in its spectrum matched that of the D3 line observed in the spectrum of the Sun; the new element of helium was thus conclusively identified. In 1903 Ramsay and Frederick Soddy further determined that helium is a product of the spontaneous disintegration of radioactive substances.
It takes two protons to make a helium atom. The difference between isotopes is the number of neutrons. Helium has seven known isotopes, ranging from He-3 to He-9. Most of these isotopes have multiple decay schemes where the decay type depends on the overall energy of the nucleus and its total angular momentum quantum number.
Table (1): Properties of Helium isotopes
Physical properties 
Helium has several unusual properties. For example, it has the lowest boiling point of any element, -268.9°C (-452.0°F). The boiling point for a gas is the temperature at which the gas changes to a liquid. The freezing point of helium is -272.2°C (-458.0°F). Helium is the only gas that cannot be made into a solid simply by lowering the temperature. It is also necessary to increase the pressure on the gas to make it a solid.
At a temperature of about -271°C (-456°F), helium undergoes an unusual change. It remains a liquid, but a liquid with strange properties. The forms of helium are so different that they are given different names. Above -271°C, liquid helium is called helium I; below that temperature, it is called helium II.
Table (2): Physical properties of Helium
Helium electron configuration is 1s2 and its first ionization energy is at 2372.3 kJ/mol. Its enthalpy of fusion is 0.0138 kJ/mol and Van der waals radius is 140 picometers. It is less soluble in water than any other gas. Also it is non-flammable.
Helium is generated underground by the radioactive decay of heavy elements such as uranium and thorium. Part of the radiation from these elements consists of alpha particles, which form the nuclei of helium atoms. Some of this helium finds its way to the surface and enters the atmosphere, where it quickly rises and escapes into space. The rest becomes trapped under impermeable layers of rock and mixes with the natural gases that form there. The amount of helium found in various natural gas deposits varies from almost zero to as high as 4% by volume. Only about one-tenth of the working natural gas fields have economically viable concentrations of helium greater than 0.4%.
Helium is a byproduct of radioactive decay in natural gas. Therefore, since natural gas has the most amounts of helium, most specialty gas laboratories will extract Helium via natural gas. There are also small amounts of helium in the air which can also be extracted, however the process for that is expensive and rarely used.
Typically helium is separated from natural gas through a cryogenic piping system. The natural gas is pressurized, and then passed through a sieve. During this scrubbing process, helium is separated from natural gas so that only crude helium remains. At this point, since the crude helium is only about 50% pure, further purification processes are warranted.
Figure 2: Helium recovery from natural gas
The crude helium is then cooled to -315 degrees Fahrenheit so that any remaining nitrogen or methane gases become liquefied and can be easily drained from the gas. The heat on the helium is then increased and oxygen is added to the gas so that any remnant traces of hydrogen will mix with the oxygen creating water. Once the water vapors are formed, the mixture is cooled back down, and the water is drained from the mixture. Once the water has been drained, the Helium then goes into containers filled with tiny particles to further purify the gas (think of the carbon water filters in most homes today). The process is repeated until the Helium is 99.99% pure specialty gas. ,  , 
The role of helium gas in medicine
The noble gas helium has many applications owing to its distinct physical and chemical characteristics, namely: its low density, low solubility, and high thermal conductivity. Chiefly, the abundance of studies in medicine relating to helium are concentrated in its possibility of being used as an adjunct therapy in several respiratory ailments such as asthma exacerbation, COPD, ARDS, croup, and bronchiolitis. Helium gas, once believed to be biologically inert, has been recently shown to be beneficial in protecting the myocardium from ischemia by various mechanisms. Though neuroprotection of brain tissue has been documented, the mechanism by which it does so has yet to be made clear. Surgeons are exploring using helium instead of carbon dioxide to insufflate the abdomen of patients undergoing laparoscopic abdominal procedures due to its superiority in preventing respiratory acidosis in patients with comorbid conditions that cause carbon dioxide retention. Newly discovered applications in Pulmonary MRI radiology and imaging of organs in very fine detail using Helium Ion Microscopy has opened exciting new possibilities for the use of helium gas in technologically advanced fields of medicine.
|Figure 3: Helium atoms to generate the red laser light used in barcode readers|
The laser generated by a barcode reader is actually produced using Helium and Neon atoms, A mixture of about 85% He and 15% Ne is placed in a thing tube. Electricity is then passed through the tube. This puts some of the He atoms in an excited state, in which one of their electrons has additional energy beyond a normal electron. Such excited He atoms are in constant motion in the tube, along with the other He and Ne atoms.
When an excited He atom collides with a Ne atom, it transfers its energy to the Neon.
The result is a Ne atom in its excited state. The Ne atom can shed some or all this energy by emitting light of different wavelengths. The most common light emitted has a wavelength of 632.8 nm, making it red in color. Other possible wavelengths and colors are 612 nm (orange), 594 nm (yellow) or 543.5 nm (green).
Helium is applied as a shielding gas in arc welding and plasma arc welding due to its highest ionization potential of any atom. The protective atmosphere of helium around the welding site prevents that the metal oxidizes in the molten state. The high ionization potential of helium enables the plasma arc welding of exotic metals such as titanium, zirconium, magnesium and aluminum alloys used in construction, shipbuilding and aerospace. As shielding gas helium can be substituted by argon or hydrogen, however for plasma arc welding of certain materials like titanium helium cannot substituted, because helium is the only gas with high enough thermal activity to be safe.
Moderation of positive muons by helium gas
It has presented the working principle of the frictional cooling of µ+ by He gas within an electric ﬁeld and performed a simulation study based on a preliminary scheme. The result shows that frictional cooling with He gas could be a promising method for the slow µ+ production at EMuS. For the FCD experiment with protons, progress on both simulation and experiment has been worked on. Also it has presented the current status and future planning on the resolving of the critical issue in our frictional cooling scheme, i.e., the electric discharges inside the He gas.
Helium gas in balloons
To get a floating balloon, you want a gas which is as light as possible. Helium is quite a lot lighter than air weight. It is about and eighth of the density of air. Hydrogen is about a sixteenth the density of air. So, it will float in air and will even float upwards. You would have thought that hydrogen would be a better gas as it would give slightly more lift than helium because it’s lighter. This is true. The problem is hydrogen is explosive and if you have children running around with balloons that could catch fire and blow up in their faces, it may have some health and safety implications. The other thing is that although hydrogen is half as heavy as helium it doesn’t give you twice as much lift because the amount of lift you get is in its difference in density with [respect to] air. It’s actually only another sixteenth of the density of air. It’s a little bit better but not very much, so it’s not worth the danger.
Helium is quite expensive, though, because it’s a limited resource here on the planet. It’s only created by radioactive decay on Earth. Atomic nucleuses emitting alpha particles that are actually helium nucleuses. They slow down and gain some electrons and turn into a helium atom. It tends to be found in oil wells where you get a gas-proof layer of rock above a load of rocks containing radioactive elements. They break down to helium. It floats up and gets trapped, often at the top of an oil well. The amount of helium that we can access cheaply is very limited because not all our oil wells have it.
Gas quenching with Helium
Gas quenching in vacuum furnaces is an increasingly attractive option because it has a low environmental impact and the least distortion of parts being treated. Whilst nitrogen is by far the most common quenching gas, helium is a viable option where higher cooling rates are required, particularly for carburised components.
When components from a conventional vacuum furnace cycle are quenched, the helium is unlikely to be significantly contaminated, which simplifies recycling. In this case it may well be possible to use a simple point of use system where only particulates are removed. However, if items from a vacuum carburising cycle, for example, are being quenched, some contamination of the helium is inevitable even if the quenching is carried out in a separate cold wall chamber. Quench gas recycle systems are not technologically complex, but can be technically challenging, and may be desirable on the grounds of raw material cost or safety. They can often be uneconomical, even for helium, without careful consideration at the specification phase so a knowledgeable system provider is essential.
Inhaling of Helium gas
When you inhale helium, it affects the timbre of your voice, because helium is much less dense than air. The dangers of helium inhalation are real although it may seem like harmless fun. It is an asphyxiant, causing dizziness or unconsciousness. In addition to generalise hypoxia, it can cause disorientation and even death. Inhaling it can even cause a ruptured lung. There is a well-known party trick where people suck gas out of helium balloons to talk funny. However, most people don’t know how dangerous helium is. Inhaling helium is dangerous.
Helium is used to test critical automotive parts such as radiator heat exchangers, air conditioning components, fuel tanks and torque converters to ensure they meet quality specifications. It is also used in combination with argon as a source of inflation in a growing number of airbags.
Also, in combination with oxygen, helium is used in diving to help eliminate nitrogen narcosis, reduce breathing resistance at depth, and shorten decompression stops. Known as heliox, the mixture allows divers to reach greater depths for longer periods of time. The deeper the dive, the higher the concentration of helium, allowing divers to explore more and weld longer.
Different valve outlet connections are used based on national or regional standards. In North America, the Compressed Gas Association (CGA) recommends three different connections for helium, depending on the pressure of the container. In addition, a high-integrity connection known also as a Diameter Index Safety System (DISS) connection has also been assigned to helium. Cylinders containing helium at pressures up to 3,000 psig use a CGA 580; cylinders containing pressure between 3,001 psig and 5,500 psig use a CGA 680; and pressures between 5,501 psig and 7,500 psig use a CGA 677. The DISS connection assigned to helium is the DISS 718. For detailed drawings of these connections, consult Compressed Gas Association Pamphlet V-1.
Shipment of gaseous helium
Compliance with applicable Dangerous Goods regulations is required for all shipments by motor freight, rail, air and water. These regulations describe the marking, labeling, placarding, and shipping papers required. International shipments by air must comply with International Air Transport Association/International Civil Air Organization (IATA/ICAO) Dangerous Goods regulations. Final acceptance for air transport is at the discretion of the airline. International shipments by water must comply with International Maritime Organization (IMO) regulations.
Provide adequate ventilation where helium is being used. Provide monitoring for areas where oxygen displacement may occur. A 19.5% oxygen concentration in the air is the minimum recommended for working without special breathing equipment.
The worldwide helium shortage affects everything from MRIs to rockets
Oil companies harvest helium trapped deep beneath the Earth’s surface, in natural gas chambers. Radioactive decay causes uranium rock to disperse helium into natural gas chambers over millions of years. It’s a slow process and finding the helium can be even more challenging. Almost every known helium reserve on the planet was discovered by accident, and the helium was merely a byproduct of natural gas harvesting.
Potential alternatives to Helium
Applications requiring temperatures of below -256°C will still require liquid Helium, but alternatives are currently available for cooling of MRI scanner magnets and other applications requiring super conductors. Liquid Nitrogen can be used in some cooling systems and there are now a number of companies who specialise in water-cooling ‘chiller’ solutions for cooling of MRIs.
Shielding gas for welding
Helium is commonly used as a shield gas for non-ferrous welding. Argon can be used instead of Helium and is preferred for certain types of metal.
Deep sea diving gases
Helium is commonly mixed with oxygen to prevent deep sea divers developing Nitrogen narcosis symptoms, but Hydrogen/Oxygen mixtures are also used for deep diving and may be increasingly used as Helium prices rise.
Table 3: Gas cylinder color code 
When transporting a cylinder by car ensure that the vehicle is well ventilated, and the cylinder is well secured. Ensure cylinders are stored in well ventilated areas, away from direct heat. Always wear eye protection when using a cylinder. When inflating balloons always point the balloon and inflator away from you. Remember to close the cylinder valve after use. Always use a proper trolley for moving large cylinders, even for a short distance.
|Figure 4: MSDS of Helium|
Always fasten the cylinder to a secure support in an upright position when in use. Cylinders can cause serious injury if they fall over or roll onto you. Always keep cylinders away from children. Responsible adults only should use cylinders and other equipment.
Do not deliberately inhale Balloonium helium. Although not poisonous it can result in asphyxiation. Never open the cylinder valve without fitting an inflator, and then open the valve slowly. Never use equipment which may be damaged.
Helium is a natural, inert gas. Most helium is found in natural gas fields. We can extract helium from rich natural gas fields and use it safely without harming the environment. Since helium is a finite resource, it is important to use helium recovery and recycling technologies.
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