L (+) Potassium Sodium Tartrate

P otassium 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.

Chemical Name Potassium Sodium Tartrate;
Potassium Sodium Tartrate Tetrahydrat;
2,3-dihydroxy- (2R,3R)-, monopotassium monosodiumsalt;
Rochelle salt
Alkaline Tartrate
Molecular Formula KNaC4H4O6·4H2O
Structural Formula
Molecular Weight 282.23
CAS No 6381-59-5 (dihydrate)
Character Colorless crystals or white crystal; specific gravity is 1.79; PH value is 6.8~8; the melting point is 70~80°C; Have efflorescence in the heat air, lose some water when heated to 60°C, and lose 3 water molecules at 100°C, become salt without water at 215°C. Freely soluble in water, insoluble in ethyl alcohol
Storage Keep in an avoid light and dry place. Seal preservation
Quality Standard British Pharmacopoeia
Term of validity 2 years


  • Food

    Used as baking powder in food industry;

    It can be used as a laxatives and food additives (E Numbers for E337);

  • Medicine

    It is used in medicine, reagent, mirror industry as reducing agent, the monitoring of the raw sugar in the food;

  • Telecommunication

    Widely used to produce telecommunication equipment such as crystal loudspeakers, crystal microphones and piezoelectric element;

  • Industry

    Used in chemical fertilizer industry as ADA desulfurizer.

Test Item Limit
Content (No Water particles %) 99 ~101
Solution appearance Clear
Specific rotatory power[a]D25 +21.0~+23.0º
Chloridion (mg/kg) <40
Sulfate (mg/kg) ≤50
Lead (m/kg) <10
Ammonium ion (mg.kg) <20
Calcium (mg/kg) ≤200
Iron (Fe2+ mg/kg) <10
Water (%) 24.0~26.5