Difference between revisions of "Lithium"

Revision as of 18:01, 25 September 2015

Lithium is a an alkali metal, the lightest metal and least dense solid element at room temperature, with the atomic number 3. It is soft, silvery-white metal, with a density of 534 kg/m³. It is highly reactive, and it is usually stored in mineral oil. However, because of its extremely low density, it floats in mineral oil, storing the metal proves to be difficult.

Properties

Chemical

Lithium, like all the alkali metals reacts violently with water, releasing hydrogen and can ignite, but this reaction is slightly less violent than the other alkali metals. In open air, it quickly forms a layer of oxide as well as nitride, and if the air also contains water vapors and carbon dioxide, lithium hydroxide and lithium carbonate. Lithium will burn in air, and it tends to burn with a red-crimson flame. As noted by NurdRage, in his video where he extracted lithium from an energizer battery, this flame is incredibly bright, so welding goggles should be used if this reaction is attempted. Such fires are difficult to extinguish, requiring dry powder extinguishers (class D).

Lithium is also a strong reducing agent. It is also used in organometallic synthesis in the form of organolithium compounds such as n-butyllithium and tert-butyllithium, although they are extremely rarely used by the amateur chemist, mainly because they're very dangerous (pyrophoric and caustic). Molten lithium is probably the most powerful reducing agent known, and will explode on contact with almost anything non-metallic, including wood, glass and concrete.

Contrary to popular belief, lithium, not cesium, is the most reactive element on the periodic table. It has the lowest reduction potential in aqueous solution, and gram-for-gram (as well as mole-for-mole) has a higher energy content than cesium.

Lithium metal is able to dissolve in anhydrous ammonia and ethylenediamine, forming its electride salt.

Physical

Lithium is a soft, silver-white metal. It is soft enough to be cut with a knife.

Lithium has the highest specific heat capacity of any solid element, 3.58 kJ/(kg*K), the highest of all solids. Because of this, lithium metal is often used in coolants for heat transfer applications.^[1]

Lithium has a density of only 534 kg/m³, making it the lightest metal and solid element at standard conditions. It is lighter than any hydrocarbon oils, which causes the metal to float in the oil is stored. The only organic hydrocarbons lighter than lithium are liquid methane (465 kg/m³), liquid propane (493.5 kg/m³), liquid propylene (514.4 kg/m³).^[2] Since these solvents are liquid only at very low temperatures or under high pressure, storing lithium in them is impractical.

In addition, lithium has the highest melting point of all alkali metals, at roughly 180 degrees Celsius. Because of this, it is difficult to melt under oil (a common tactic for removing tarnish from the other alkali metals). Molten lithium is extremely reactive and will react with almost all ceramic materials, therefore lithium is only melted in crucibles made of special metals, such as molybdenum. It also has a high boiling point, of 1330 °C.

Lithium dissolves in liquid ammonia.^[3]

Availability

Lithium can be extracted from lithium batteries, as shown by NurdRage is his video. It comes as a long sheet of lithium metal, that quickly tarnishes in air. It's risky, as the battery can short and overheat. One safer method is to use a pipe cutter and split the battery case in the middle. Larger quantities of lithium can be bought from Galliumsource, though it's pretty expensive (150$/100g). Due to its low molar mass, one may get away with using much smaller amounts of lithium than expected.

In recent years, some jurisdictions in United States limit the sale of lithium batteries, as elemental lithium can be used to reduce pseudoephedrine and ephedrine to the illegal drug methamphetamine.

Preparation

Industrially, elemental lithium is produced electrolytically from a mixture of fused 55% lithium chloride and 45% potassium chloride at about 450 ^oC. As molten lithium is highly reactive, this process should be performed in installations made of corrosion resistant alloys.

Projects

• Buthyllithium synthesis (DANGER! PYROPHORIC!)
• Isolation of reactive metals, including lanthanides
• Lithium lubricating grease
• Aluminium-lithium alloys
• Cesium synthesis by distillation (DANGER!)

Safety

Handling

Contrary to what one may think, NEVER HANDLE LITHIUM WITH GLOVES OF ANY KIND! You can easily tell if your hands are wet, but not if your gloves are wet, and if you get lithium wet (or it ignites) while handling it with gloves, it will burn through your gloves (and potentially explode) faster than you can remove them.^[4] Pliers are another safe option. Glove boxes are also very good for work with lithium.

Toxicity

Breathing lithium dust or lithium compounds irritate the nose and throat, while higher exposure can cause a buildup of fluid in the lungs, leading to pulmonary edema. Acetic acid a good neutralizing agent.

Storage

Like every other alkali metal, it must be kept away from any fire source. Keeping lithium under mineral oil is difficult because lithium floats on mineral oil, though a small rock may be used to keep it down. The best solution is to keep it in an inert argon atmosphere (nitrogen will react to form lithium nitride). Sulfur hexafluoride can also be used, except when it's molten (it will react).

Disposal

Lithium compounds are not particularly dangerous to the environment, but it's recommended to recycle them when possible.

References

1. ↑ http://hilltop.bradley.edu/~spost/THERMO/solidcp.pdf
2. ↑ http://www.engineeringtoolbox.com/liquids-densities-d_743.html
3. ↑ http://pubs.acs.org/doi/abs/10.1021/j150343a013
4. ↑ Thunderf00t knows what he's talking about. https://www.youtube.com/watch?v=Nn3M1hfjxMU

Relevant Sciencemadness threads

• Lithium electride in ethylenediamine