Potassium sodium tartrate

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Potassium sodium tartrate
Potassium sodium tartrate bottle and sample.jpg
Potassium sodium tartrate aka Rochelle salt
Names
IUPAC name
Sodium potassium L(+)-tartrate tetrahydrate
Other names
E337
Rochelle salt
Seignette salt
Properties
KNaC4H4O6 (anhydrous)
KNaC4H4O6·4H2O (tetrahydrate)
Molar mass 210.16 g/mol (anhydrous)
282.1 g/mol (tetrahydrate)
Appearance Large colorless monoclinic needles
Odor Odorless
Density 1.79 g/cm3
Melting point 75 °C (167 °F; 348 K)
Boiling point 220 °C (428 °F; 493 K) (decomposes)
26 g/100 ml (0 °C)
47.4 g/100 ml (6 °C)
66 g/100 ml (26 °C)
Solubility Insoluble in acetone, ethanol
Vapor pressure ~0 mmHg
Hazards
Safety data sheet Sigma-Aldrich (tetrahydrate)
Related compounds
Related compounds
Tartaric acid
Potassium antimony tartrate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Potassium sodium tartrate (tetrahydrate), more commonly known as Rochelle salt, is a double salt of tartaric acid first prepared (around 1675) by an apothecary, Pierre Seignette, of La Rochelle, France.

Properties

Chemical

Addition of a strong acid, like hydrochloric acid, will give tartaric acid.

Physical

Potassium sodium tartrate is a white crystalline solid, soluble in water.

Availability

Rochelle's salt can be bought from chemical suppliers, in bulk, and it's fairly cheap.

Potassium sodium tartrate is readily available on eBay and Amazon.

Preparation

Can be prepared by neutralizing tartaric acid with sodium and potassium carbonates, bicarbonates or hydroxides.

A much simpler and straightforward route involves neutralization of potassium bitartrate with sodium hydroxide.

Projects

Handling

Safety

Potassium sodium tartrate has low toxicity, though the dry salt can be irritating to skin, mouth, nose and eyes.

Ingestion of large amounts of Rochelle salt will lead to bloating and diarrhea.

Storage

Potassium sodium tartrate is very deliquescent and should be stored in a sealed container.

Disposal

Dissolve in large excess of water and put down drain.

References

Relevant Sciencemadness threads