About Lithium sulfate monohydrate

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 lanthanoid sulfates.
Lithium sulfate  crystals, being piezoelectric, are also used in ultrasound-type non-destructive testing because they are very efficient sound generators. However, they do suffer in this application because of their water solubility.
Lithium sulfate is used to treat bipolar disorder (see lithium pharmacology).