What is Rochelle Salt?
Rochelle salt is a natural salt. Its chemical name is sodium potassium tartrate tetrahydrate. Rochelle salt is also called a double salt of tartaric acid. The first production of the same was done in the year 1675.
The discoverer of the Rochelle salt was an apothecary named Pierre Seignette, born in the city of La Rochelle, France.
Also, sodium potassium tartrate and monopotassium were the first constituents to possess the piezoelectric property. The salt is also known as Seignette Salt, which was named so after him.
On this page, you will find all the properties of Rochelle salt crystals along with the various sodium potassium tartrate uses in detail.
Properties of Rochelle Salt
The Rochelle salt comes from a natural crystalline acid settled on the inside of the wine barrels at the cellars.
Certainly, every chemical compound carries various properties with itself, which we will discuss one-by-one.
The Properties are as follows:
Chemical properties
Physical properties
Ingredients/composition
Strength
Storage and stability
Rochelle Salt Crystal
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Rochelle Salt Structure
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Rochelle Salt Chemical Properties
1. Synonyms
Seignette Salt
Alkyl group - (2R, 3R) - 2,3 dihydroxybutane - 1,4 - dioïc acid
Potassium Sodium Salt, tetrahydrate
L (+) Tartaric Acid monosodium monoPotassium Tartrate
Butanedioïc acid, 2, 3 - dihydroxy -, [R(R*,R*)]
Monopotassium monosodium salt, tetrahydrate
Potassium sodium Tartrate
Monopotassium, monosodium Tartrate, tetrahydrate
2. Chemical Formula
Rochelle Salt Formula - C4H4O6KNa. 4H2O
Expanded chemical formula: KOOCCH(OH)CH(OH)COONa. 4H2O
Molecular mass - 282.23 g/mol
Rochelle Salt Physical Properties
Rochelle Salt Storage and Stability
We must keep the Rochelle Salt in an airtight packing and stock in a dry place, away from humidity and normal conditions of temperature.
The Rochelle slat is a stable compound that does not alter with time if the above advice is respected. Also, the use-by date is given according to the regulation, accordingly, it is two years.
This salt has a tendency to become caked, and therefore, long storage is not suggested especially for the powder grade.
Household Rochelle Salt Preparation
Ingredients Required:
We can prepare a Rochelle salt by using the following kitchen ingredients:
Cream of Tartar
Washing Soda
Sodium Carbonate (which you can get by heating baking soda or sodium bicarbonate in a 275°F oven for an hour).
1/2 kg (1 pound/lb) of baking soda (sodium bicarbonate, NaHCO3)
200 grams (7 oz) of tartar cream, i.e., potassium bitartrate, KHC4H4O6
250 ml (1 cup) of distilled water
Steps to Prepare Rochelle Salt are as Follows:
Step 1: L Warmth a combination of around 80 grams cream of tartar in 100 milliliters of water to a bubble in a pot.
Step 2: Gradually mix in sodium carbonate. The arrangement will rise after every expansion. Keep adding sodium carbonate until no more air pockets structure.
Step 3: Chill this arrangement in the cooler. Translucent Rochelle salt will shape on the lower part of the container.
Step 4: Eliminate the Rochelle salt. On the off chance that you redissolve it in a modest quantity of clean water, you can utilize this material to develop single gems.
The way to develop Rochelle salt precious stones is to utilize the base measure of water expected to break up the strong. Use bubbling water to expand the dissolvability of the salt. You may wish to utilize a seed gem to invigorate development on a solitary gem instead of all through the compartment.
Commercial Rochelle Salt Preparation
The beginning material is tartar with a base tartaric corrosive substance of 68 %. This is first disintegrated in water or in the mother alcohol of a past cluster. It is then basified with hot saturated sodium hydroxide for pH 8, decolorized with actuated charcoal, and synthetically decontaminated prior to being separated.
The filtrate is vanished to 42 °Bé at 100 °C and passed to granulators in which Seignette's salt takes shape on sluggish cooling. The salt is isolated from the mother alcohol by centrifugation, joined by the washing of the granules, and is dried in a rotational heater and sieved prior to bundling. Financially advertised grain sizes range from 2000 μm to < 250 μm (powder).
Bigger precious stones of Rochelle salt have been developed under states of decreased gravity and convection onboard Skylab.
Rochelle salt gems will start to get dried out when the general moistness drops to around 30% and will start to disintegrate at relative humidities over 84%.
Sodium Potassium Tartrate Uses
Potassium sodium tartrate and monopotassium phosphate were the principal materials found to display piezoelectricity.
Rochelle salt uses were crucial back in the mid-20th century, where Rochelle salt crystals were found in gramophone (phono) pick-ups, microphones, and earpieces during the post Worldwar II. Furthermore, Rochelle salt crystals became a boom in the consumer electronics domain.
Such transducers had an extraordinarily high yield with average get cartridge yields of as much as 2 volts or more. Rochelle salt is deliquescent so any transducers dependent on the material disintegrated whenever put away in soggy conditions.
It has been utilized restoratively as a purgative. It has likewise been utilized during the time spent silvering mirrors. It is an element of Fehling's answer (reagent for lessening sugars). It is utilized in electroplating, in gadgets and piezoelectricity, and as a burning gas pedal in cigarette paper (like an oxidizer in fireworks).
In a natural blend, it is utilized in fluid workups to separate emulsions, especially for responses in which an aluminum-based hydride reagent was utilized. Sodium Potassium tartrate is likewise significant in the food business.
It is a typical precipitant in protein crystallography and is additionally a fixing in the Biuret reagent which is utilized to quantify protein focus. This fixing keeps up cupric particles in the arrangement at an antacid pH.
Furthermore, the substance is utilized as a food added substance to contribute a pungent, cooling taste. It is fixed in helpful magnetism reagents, like Fehling's answer and Biuret reagent.
Do You Know?
Sir David Brewster showed piezoelectricity by utilizing Rochelle salt in 1824. He named the impact pyroelectricity.
Pyroelectricity is a property of certain gems portrayed by regular electrical polarization. All in all, a pyroelectric material can create a transitory voltage when warmed or cooled.
Additionally, Brewster named the impact, it was first referred to by the Greek rationalist Theophrastus (c. 314 BC) regarding the capacity of tourmaline to draw in straw or sawdust when warmed.
FAQs on Rochelle Salt
1. What exactly is Rochelle Salt, and what is its chemical formula?
Rochelle Salt is the common name for potassium sodium tartrate tetrahydrate. It is a double salt of tartaric acid, meaning it contains two different cations, potassium (K⁺) and sodium (Na⁺), in its crystal lattice. Its chemical formula is KNaC₄H₄O₆·4H₂O, indicating it is a hydrated salt with four molecules of water of crystallisation.
2. What is the official IUPAC name for Rochelle Salt?
The systematic IUPAC name for Rochelle Salt is Potassium sodium (2R,3R)-2,3-dihydroxybutanedioate tetrahydrate. This name precisely describes its components: 'Potassium sodium' indicates the two cations, '(2R,3R)-2,3-dihydroxybutanedioate' describes the tartrate anion with its specific stereochemistry, and 'tetrahydrate' refers to the four water molecules.
3. What are the primary applications and uses of Rochelle Salt in chemistry and industry?
Rochelle Salt has several important applications based on its unique chemical and physical properties. Key uses include:
- Fehling's Solution: It is a crucial component of Fehling's solution B, used to test for reducing sugars and aldehydes.
- Piezoelectricity: It was one of the first materials discovered to exhibit piezoelectricity, converting mechanical pressure into electrical voltage, and was used in early microphones and phonograph pickups.
- Silvering Mirrors: It acts as a reducing agent in the Tollen's test process to deposit a uniform layer of silver onto glass.
- Food Additive: It is used as an emulsifier and sequestrant in food products, identified by the E number E337.
- Electroplating: It is used in electroplating baths to form complexes with metal ions.
4. Is Rochelle Salt the same thing as Fehling's solution?
No, Rochelle Salt is not the same as Fehling's solution, but it is an essential ingredient of it. Fehling's solution consists of two parts: Fehling's A (an aqueous solution of copper(II) sulfate) and Fehling's B (an aqueous solution of Rochelle Salt and sodium hydroxide). The role of Rochelle Salt is to act as a chelating agent, keeping the copper(II) ions dissolved in the alkaline solution and preventing them from precipitating as copper(II) hydroxide.
5. What is the significance of the crystal structure of Rochelle Salt?
Rochelle Salt crystallises in the orthorhombic system. The significance of this specific crystal structure is that it lacks a centre of symmetry, which is a prerequisite for a material to exhibit the piezoelectric effect. This effect, where the crystal generates an electric charge in response to mechanical stress, is one of Rochelle Salt's most notable properties and is a direct consequence of its atomic arrangement within the orthorhombic lattice.
6. How does the denticity of the tartrate ion in Rochelle Salt contribute to its function in chemical tests?
The tartrate ion (C₄H₄O₆²⁻) from Rochelle Salt acts as a bidentate ligand. This means it can bind to a central metal ion, like Cu²⁺ in Fehling's solution, through two points simultaneously. It uses its carboxylate and hydroxyl groups to form a stable chelate complex with the copper ion. This chelation is crucial because it sequesters the Cu²⁺ ions, keeping them in solution in the strongly alkaline conditions of the test, ready to be reduced by an aldehyde.
7. Is it safe to eat Rochelle Salt?
While Rochelle Salt is used as a food additive (E337), it is also known for its laxative properties. It was historically sold for this purpose. Therefore, it should not be consumed directly or in large quantities. Its presence in food products is highly regulated and in very small, safe amounts where it functions as an emulsifier or acidity regulator. For any use other than as a regulated food ingredient, it is not considered safe for consumption.
8. How is Rochelle Salt different from Cream of Tartar, another common tartrate?
Although both are derived from tartaric acid, they are different compounds. Rochelle Salt is potassium sodium tartrate (KNaC₄H₄O₆), a double salt containing both potassium and sodium ions. In contrast, Cream of Tartar is potassium bitartrate or potassium hydrogen tartrate (KC₄H₅O₆), an acidic salt containing only potassium ions. This difference in composition leads to different uses: Rochelle Salt is primarily used in chemical reagents like Fehling's solution, while Cream of Tartar is mainly used in baking as a leavening agent and stabiliser.
