Vill ni att jag lägger upp en av mina texter om kemi, till er? Om kväve, N.

Nitrogen can be used as an oxidizing agent (just think how close ?N? is placed to ?O? on the periodic table, and that both atoms are non-metals with similar properties), and a good example of it we see in this classical reaction: N2 + 3 H2 ---> 2 NH3, that is what happens when the industry produce ammonia (to get ammonium nitrate in next step) that can be used as a fertilizer. The oxidizing agent nitrogen is gaining electrons, and became reduced by hydrogen. How we usually produce liquid nitrogen is thanks to a cryogenic gas plant, which is an industrial facility that separates air during distillation processes. That is the source from where the very pure gas and liquid nitrogen product comes from, and  the process is happening during very cold conditions. At room temperature nitrogen is always a gas. We have to have in mind that the melting point of N2 is -210 degrees Celsius, and the boiling point is -192 Celsius, and it will always be found in nature in gas form.

The company that purchases the product will receive product specific information about the purity of the liquid and pressure in the tanks or cylinders. If the consumption of nitrogen is not very big, then you buy it in dewars, that are non-pressurized small cans. Now let?s talk about different types of nitrogen. The isotopes that are stable (non-radioactive, and they are not spontaneously rearranging themselves because of too many neutrons to bear in the core) are nitrogen-14 (the most common, making up 99,6% of total natural nitrogen) and nitrogen-15, and they are being produced in the CNO cycle. That is a carbon-nitrogen-oxygen cycle that occurs in the stars, and when a type of ?hydrogen fusion? happens, we get helium as the product. New fusions will occur on some helium also, and we will get carbon (life forms are made of mostly oxygen, carbon, hydrogen and nitrogen (3,2%)). Fourteen nitrogen radioisotopes are known. They behave like nitrogen do but they are short-lived.

Nitrogen-13 is an important radioisotope. It is used in positron emission tomography (PET) mainly of the reason that its half-life is long enough to fulfill its purpose at the hospital, and because it can tag ammonia molecules and other compounds in the body (depending on what part of the body the doctors are scanning) very effectively. Tracers coming in into the body from ?13 N? are relatively small. The dose needed for the patient is normally 2 mSv, which is little compared with for example rubidium-82, when the dose often is 15 mSv. The radioactive atoms are giving off positively charged positrons, and when you combine one positron with one electron they destroy each other, and in that moment gamma rays will be detected. Doctors are tracking tracers in the human body (that was inserted at the hospital) to reveal the organs function in 3 dimensions. Many nitrogen isotopes are synthetically produced, and 13 N is one of them. These isotopes are ranging from 12 N - 23 N.

The picture is borrowed from google.

www.sciencedirect.com/science/article/abs/pii/S2352492822011606~:text=The%20electrochemical%20nitrogen%20reduction%20reaction%20%28NRR%29%20catalyzes%20the,O%20under%20ambient%20conditions%20to%20form%20NH%203.

https://www.chemicalaid.com/tools/redoxreaction.php?equation=N+%2B+H+%3D+NH3

scienceatyourdoorstep.com/2020/10/19/what-happens-after-helium-fusion/

https://www.bing.com/videos/search?q=positron+emission+tomography+youtube&docid=608046195819833721&mid=11EEA5960DA26DF0009911EEA5960DA26DF00099&view=detail&FORM=VIRE

What is nitrogen, and how to warehouse it, when it?s in liquid form (Part 2 of 2).

Uses of liquid nitrogen differ from uses of it in gas form. We are focusing on the first mentioned state of aggregation. It is used first and foremost to keep various goods cold and it is a refrigerant of raw materials, medicines, food products, etc. In laboratories, nitrogen in liquid form is used to cool chemical reactions, for testing electronic devices, shrink fitting (which is joining for example metallic parts together during an installation) and in other areas this is used for pipe freezing. We are going to explain all these 4 latter uses. Liquid nitrogen is nontoxic and noncorrosive, but the dangers with it are that you can get oxygen deficiency or get frostbite, because what?s inside this coolant technology is of such extremely low temperature. Liquid nitrogen and liquid carbon dioxide are used in the cryogenic cooling technology where they have many advantages compared with mechanically cooled systems. The last one has many different components which makes it both heavy and complicated.

In case of changed planning and redecoration at the laboratory, it does not cost so much to relocate a vacuum insulated tube compared with moving a freezer, compressor, heat exchanger rewinds, ventilators and many other things included. Chilling mechanically is also not as effective as using N2-gas, and you can only get down to above -55 C with the first mentioned. With an oxygen monitor on the wall and an alarming system you and your staff are very safe while handling liquid nitrogen, that is held together in pairs with triple bonding, that require large amounts of energy if you want to try to break them up. But the intermolecular bonding is instead being held together with van der Waals bindings, because of temporary delta minus and plus charges on two poles. The reason is that electrons are never still, and sometimes they are both in the same place on the diatomic molecule in question (same with other nonpolar molecules). In such moments, van der Waals arises.

The molecules influence each other a lot to form such bonds in question. A temporary positive pole brings out a temporary negative pole in someone else. This is how they function, and it is incorrect to claim that van der Waals bindings between molecules are always weak. Hydrocarbons teach us that the longer the chain, and the more van der Waals bonds there are, the higher the boiling point. The alkane (where there are only single bonds between the carbons) decane, C10H22, has a boiling point on 174 C, with its van der Waals bindings. But let?s go back to the diatomic molecule N2. It can be used in a fire suppression system because it?s reducing the oxygen which will put out the fire. No byproducts will be produced during that and N2 itself will not rot. In laboratories it can cool down many chemical reactions the same way. Also, let?s not forget the scientist?s tool that is called cryo-EM, when you prepare samples of any kind or illustrate protein or chemical compound patterns.  

Cryo-EM technology allows you to see proteins in a sharp image, because one effectively freezes them in a thin layer of liquid and then observes them. It?s not like with the X-ray that proteins must lie still and be tightly packed in a crystal structure, otherwise your image will be completely blurred. Same thing with gases, sometimes you want the ethane gas to become a liquid for various reasons, for example during a study on the molecules in the lab. Then you use the liquid N2 on the C2H6 gas. Now we will explain that part about testing electric devices with the help of N2. NASA (the Space Administration) tests a lot if their machines and metals can withstand extreme cold, but you can test the endurance of many different devices as well. In an environmental chamber you can observe if the company?s industrial products or materials tolerate for example a lot of moisture, if the material will hold if it?s exposed to salt, or if it can withstand extreme temperature fluctuations? (N2 is used here).

Shrink fitting with N2. This is when you have metal parts that you either want to put together or separate from each other. You first need to heat them to between 150-300 Celsius, and when the metal has expanded then you relocate the parts with your equipment, and when it?s done you cool the device down with a lot with liquid nitrogen. The metals will then contract by the huge temperature change and sit together in a new way (if that was the goal), and then they are shrink fitted thanks to thermal (heat-related) expansion. With N2 you can also do pipe freezing, which is when you want to create a solid plug of the liquid inside a pipe, so the activity inside becomes still. That allows you to modify the pipe on one side or to pressure test the pipe. N2 cools down an optional small part of the tube from the outside (you put on a fit freeze jacket). Remember to always wear protective glasses, and gloves (preferably a little too large, so you can pull these off quickly).