Lithium sulfate is soluble in water, though it does not follow the usual trend of solubility versus temperature — its solubility in water decreases with increasing temperature, as its dissolution is an exothermic process. This property is shared with few inorganic compounds, such as the lanthanoidsulfates. Lithium sulfate crystals, being piezoelectric, are also used in ultrasound-type non-destructive testing because they are very efficient sound receivers. However, they do suffer in this application because of their water solubility. Since it has hygroscopic properties, the most common form of lithium sulfate is lithium sulfate monohydrate. Anhydrous lithium sulfate has a density of 2.22 g/cm3 but, weighing lithium sulfate anhydrous can become cumbersome as it must be done in a water lacking atmosphere. Lithium sulfate has pyroelectric properties. When aqueous lithium sulfate is heated, the electrical conductivity also increases. The molarity of lithium sulfate also plays a role in the electrical conductivity; optimal conductivity is achieved at 2M and then decreases. When solid lithium sulfate is dissolved in water it has an endothermic disassociation. This is different than sodium sulfate which has an exothermic disassociation. The exact energy of disassociation is difficult to quantify as it seems relative to the mols of the salt added. Small amounts of dissolved lithium sulfate have a much greater temperature change than large amounts.
Crystal properties
Lithium sulfate has two different crystal phases. In common phase II form, Lithium sulfate has a sphenoidal monoclinic crystal system that has edge lengths of a = 8.23Å b = 4.95Å c = 8.47Å β = 107.98°. When lithium sulfate is heated passed 130 ℃ it changes to a water free state but retains its crystal structure. It is not until 575 ℃ when there is a transformation from phase II to phase I. The crystal structure changes to a face centered cubic crystal system, with an edge length of 7.07Å. During this phase change, the density of lithium sulfate changes from 2.22 to 2.07 g/cm3.
Uses
Lithium sulfate is used to treat bipolar disorder. Lithium sulfate is researched as a potential component of ion conducting glasses. Transparent conducting film is a highly investigated topic as they are used in applications such as solar panels and the potential for a new class of battery. In these applications, it is important to have a high lithium content; the more commonly known binary lithium borate is difficult to obtain with high lithium concentrations and difficult to keep as it is hygroscopic. With the addition of lithium sulfate into the system, an easily produced, stable, high lithium concentration glass is able to be formed. Most of the current transparent ionic conducting films are made of organic plastics, and it would be ideal if an inexpensive stable inorganic glass could be developed. Lithium sulfate has been tested as an additive for Portland cement to accelerate curing with positive results. Lithium sulfate serves to speed up the hydration reaction which decreases the curing time. A concern with decreased curing time is the strength of the final product, but when tested, lithium sulfate doped Portland cement had no observable decrease in strength.
Medication
Lithium is used in psychiatry for the treatment of mania, endogenous depression, and psychosis; and also for treatment of schizophrenia. Usually lithium carbonate is applied, but sometimes lithium citrate, lithium sulfate or lithium oxybutyrate are used as alternatives. Li is not metabolized. Because of Li chemical similarity to sodium and potassium, it may interact or interfere with biochemical pathways for these substances and displace these cations from intra- or extracellular compartments of the body. Li seems to be transported out of nerve and muscle cells by the active sodium pump, although inefficiently. Lithium sulfate has a rapid gastrointestinal absorption rate, and complete following oral administration of tablets or the liquid form. It diffuses quickly into the liver and kidneys but requires 8–10 days to reach bodily equilibrium. Li produces many metabolic and neuroendocrine changes, but no conclusive evidence favors one particular mode of action. For example, Li interacts with neurohormones, particularly the biogenic amines, serotonin and norepinephrine, which provides a probable mechanism for the beneficial effects in psychiatric disorders, e.g. manias. In the CNS, Li affects nerve excitation, synaptic transmission, and neuronal metabolism. Li stabilizes serotoninergic neurotransmission.
Reactions
Lithium sulfate has been used in organic chemistry synthesis. Lithium sulfate is being used as a catalyst for the elimination reaction in changing n-butyl bromide to 1-butene at close to 100% yields at a range of 320℃ to 370℃. The yields of this reaction change dramatically if heated beyond this range as higher yields of 2-butene is formed.
