Potassium sodium tartrate (KNaC4H406), also known as Rochelle salt, is a double salt of tartaric acid. It is a colorless, odorless salt with a saline taste. It has various uses including as a laxative, to break emulsions, as a component of Fehling's reagent in protein crystallography, in biuret reagent, and as a combustion regulator in cigarette paper. It is prepared by neutralizing a solution of sodium carbonate with potassium bitartrate, boiling the solution, filtering and concentrating it to obtain crystals.

1. Potassium
Sodium
Tartrate
(KNaC4H406)
Himanshu Kumar
(MM COLLEGE OF
PHARMACY, AMBALA)

2. Structure

3. Introduction
• Potassium sodium tartrate is a
double salt of tartaric acid having the
chemical formula KNaC4H4O6. It is
also known as “Rochelle salt”. It is a
very important compound in food
industry. It was firstly prepared in
1675 in France.

4. Properties
• Molar mass – 282.1g
• Colour – colourless
• Odour – odourless
• Taste – saline
• pH – 6.5 – 8.5
• Density – 1.79 g/cmᶟ
• Melting point – 75°C or 167°F or 348K
• Boiling point – 220°C or 428°F or 493K
• Solubility in water – 26g/100ml at 0°C,
66g/100ml at
26°C
• Solubility in ethanol – insoluble

5. Uses
• It is used as a laxative.
(laxatives are medicines that helps in
resolving constipation. It is also used before
surgery to empty the bowel of fecal matter.)
• It is used to break emulsions.
(emulsions are the mixture of two liquid
phases such as water and oil which are
mutually insoluble and its either phases are
dispersed in the other liquid.)

6. Uses
• It is a component of Fehling’s reagent.
(Fehling’s reagent is comprises of two
solutions, Fehling’s solution A and Fehling’s
solution B, which is Potassium Sodium
Tartrate.)
• It is a common precipitant in protein
crystallography.
(protein crystallography is a process of
formation of regular array of individual
protein, which can be used to study the
molecular structure of protein.)

7. Uses
• It is used in biuret reagent.
(biuret reagent is used to assess the
concentration of protein.)
• It is used in cigarette paper.
(to control smoking properties,
cigarette paper contains additives that
regulate burning. Here, sodium
potassium tartrate is used as
combustion regulator.)

8. Preparation
• It is obtained by neutralizing a solution of
sodium carbonate with potassium
bitartrate.
• The solution is boiled for some time and
then allow to stand at 60°C for the
completion of reaction and the neutrality
adjusted.
• Carbon dioxide is slowly evolved.
• This solution is filtered and concentrated to
crystallisation.
KHC4H4O6 + Na2CO3→ C4H4O6KNa·4H2O

9. Identification
• When heated the salt emits an odour
of burning sugar and leaves a
residue which is alkaline to litmus
paper and gives effervescence with
acids.
• The salt gives characteristic reaction
of sodium and potassium.

10. Assay
• An accurately weighed quantity (about
2g) is heated in a silica crucible until
carbonised.
• The residue is boiled with 50ml of 0.5N
sulphuric acid.
• The solution is filtered and residue id
washed.
• The filtrate and washing are titrated for
an excess of acid with 0.5N sodium
hydroxide using methyl orange
indicator

11. The end