Description:
Colorless translucent crystals or white crystalline powder. Melting point 70-80 C, relative density 1.790. Loses 3 crystal waters at 100 C, loses all crystal waters at 130-140 C, begins to decompose at 220 C. Soluble in water, insoluble in ethanol. The aqueous solution is slightly alkaline. Tastes salty and cool.

Application:
Potassium sodium tartrate tetrahydrate, also known as Rochelle salt, is a double salt of Tartaric Acid first prepared by an apothecary, Pierre Seignette, of La Rochelle, France. Potassium Sodium Tartrate and monopotassium phosphate were the first materials discovered to exhibit piezoelectricity.This property led to its extensive use in "crystal" gramophone pick-ups, microphones and earpieces during the post-World War II consumer electronics boom of the mid-20th Century. Such transducers had an exceptionally high output with typical pick-up cartridge outputs as much as 2 volts or more. Rochelle salt is deliquescent so any transducers based on the material deteriorated if stored in damp conditions.
In the pharmaceutical industry, it is used to prepare Flynn's solution and test reducing sugar, and is used as a laxative. In the electroplating industry, it is used as chemical copper precipitation and as a complexing agent in cyanide copper plating. In the chemical industry, it is used as a desulfurizer for natural chemicalbook gas. In the food industry, it is used to prepare baking powder. In the mirror industry, it is used for silver mirror reactions, etc. As a chemical reagent, it is mainly used as a masking agent and used in biochemical tests of serum proteins.