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Sodium Carbonate


Sanskrit Name:Svarjikshara

DEFINITION:-Sodium carbonate (also known as washing soda or soda ash), Na2CO3, is a sodium salt of carbonic acid. It most commonly occurs as a crystalline heptahydrate, which readily effloresces to form a white powder, the monohydrate. It has a cooling alkaline taste, and can be extracted from the ashes of many plants. It is synthetically produced in large quantities from table salt in a process known as the Solvay process.


Sodium carbonate, also known as washing soda or soda ash, is a sodium salt of carbonic acid. Molecular formula for sodium carbonate is na2co3. It most commonly occurs as a crystalline heptahydrate which readily effloresces to form a white powder, the monohydrate. It has a cooling alkaline taste, and can be extracted from the ashes of many plants.

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sodium carbonate chemical compound, Na 2 CO 3 , soluble in water and very slightly soluble in alcohol. Pure sodium carbonate is a white, odorless powder that absorbs moisture from the air, has an alkaline taste, and forms a strongly alkaline water solution. It is one of the most basic industrial chemicals. Sodium carbonate decahydrate, Na 2 CO 3 ·10H 2 O, is a colorless, transparent crystalline compound commonly called sal soda or washing soda.

The most important use for sodium carbonate is in the manufacture of glass. When heated to very high temperatures, combined with sand (SiO2) and calcium carbonate (CaCO3), and cooled very rapidly, glass is produced.

Sodium carbonate is also used as a relatively strong base in various settings. For example, sodium carbonate is used as a pH regulator to maintain stable alkaline conditions necessary for the action of the majority of developing agents. It is a common additive in municipal pools used to neutralize the acidic effects of chlorine and raise pH. In cooking, it is sometimes used in place of sodium hydroxide for lying, especially with German pretzels and lye rolls. These dishes are treated with a solution of an alkaline substance in order to change the pH of the surface of the food and thus improve browning.

In taxidermy, sodium carbonate added to boiling water will remove flesh from the skull or bones of trophies to create the “European skull mount” or for educational display in biological and historical studies.

In chemistry, it is often used as an electrolyte. This is because electrolytes are usually salt-based, and sodium carbonate acts as a very good conductor in the process of electrolysis. Additionally, unlike chloride ions which form chlorine gas, carbonate ions are not corrosive to the anodes. It is also used as a primary standard for acid-base titrations because it is solid and air-stable, making it easy to weigh accurately.

In domestic use, it is used as a water softener during laundry. It competes with the ions magnesium and calcium in hard water and prevents them from bonding with the detergent being used. Without using washing soda, additional detergent is needed to soak up the magnesium and calcium ions. Called Washing Soda or Sal Soda  in the detergent section of stores, it effectively removes oil, grease, and alcohol stains. Sodium carbonate is also used as a descaling agent in boilers such as found in coffee pots, espresso machines, etc.

In dyeing with fiber-reactive dyes, sodium carbonate (often under a name such as soda ash fixative or soda ash activator) is used to ensure proper chemical bonding of the dye with the fibers, typically before dyeing (for tie dyes), mixed with the dye (for dye painting), or after dyeing (for immersion dyeing).

Sodium carbonate is a food additive (E500) used as an acidity regulator, anticaking agent, raising agent and stabilizer. It is one of the components of kansui, a solution of alkaline salts used to give ramen noodles their characteristic flavor and texture. Sodium carbonate is also used in the production of sherbet lollies. The cooling and fizzing sensation results from the endothermic reaction between sodium carbonate and a weak acid, commonly citric acid, releasing carbon dioxide gas, which occurs when the sherbet is moistened by saliva.

Sodium carbonate is used by the brick industry as a wetting agent to reduce the amount of water needed to extrude the clay.

In casting, it is referred to as “bonding agent” and is used to allow wet alginate to adhere to gelled alginate.

Sodium carbonate is used to encapsulate and kill mold. When mixed with water and put in a spray bottle, it is sold for its anti-mold cleaning ability. It is also used to blast off mold from wood or other materials.

Sodium carbonate is used in toothpastes, where it acts as a foaming agent, an abrasive, and to temporarily increase mouth pH.

The crystalline form of washing soda can be used to induce vomiting in dogs. A tablespoon for large breeds is sufficient to force the animal to empty the contents of its stomach.

Sodium carbonate may be used for safely cleaning silver. First, aluminium foil is added to a glass or ceramic container, and covered with very hot water and some sodium carbonate. Silver items are dipped into this “bath” to clean them, making sure the silver makes contact with the aluminium foil. Finally, the silver is rinsed in water and let to dry.

Sodium carbonate is soluble in water, but can occur naturally in arid regions, especially in the mineral deposits (evaporites) formed when seasonal lakes evaporate. Deposits of the mineral natron, natural sodium carbonate decahydrate, have been mined from dry lake bottoms in Egypt since ancient times, when natron was used in the preparation of mummies and in the early manufacture of glass. Sodium carbonate has three known forms of hydrates: sodium carbonate decahydrate (natron), sodium carbonate heptahydrate (not known in mineral form) and sodium carbonate monohydrate (mineral thermonatrite). The anhydrous mineral form of sodium carbonate is quite rare and called natrite. Sodium carbonate also erupts from Tanzania’s unique volcano Ol Doinyo Lengai , and probably erupted from other volcanoes in the past . All three mineralogical forms of sodium carbonate, as well as sodium carbonate bicarbonate, trona, are also known from ultra-alkaline pegmatitic rocks, i.e. from the Kola Peninsula.


Trona, hydrated sodium bicarbonate carbonate (Na3HCO3CO3·2H2O), is mined in several areas of the United States and provides nearly all the domestic sodium carbonate. Large natural deposits found in 1938, such as the one near Green River, Wyoming, have made mining more economical than industrial production in North America.

It is also mined out of certain alkaline lakes such as Lake Magadi in Kenya by using a basic dredging process and it is also self-regenerating so will never run out in its natural source.

Barilla and kelp
Several “halophyte” (salt tolerant) plant species and seaweed species can be processed to yield an impure form of sodium carbonate, and these sources predominated in Europe and elsewhere until the early 19th Century. The land plants (typically glassworts or saltworts) or the seaweed (typically Fucus species) were harvested, dried, and burned. The ashes were then “lixiviated” (washed with water) to form an alkali solution. This solution was boiled dry to create the final product, which was termed “soda ash;” this very old name refers to the archetypal plant source for soda ash, which was the small annual shrub Salsola soda (“barilla plant”).

The sodium carbonate concentration in soda ash varied very widely, from 2-3% for the seaweed-derived form (“kelp”), to 30% for the best barilla produced from saltwort plants in Spain. Plant and seaweed sources for soda ash, and also for the related alkali “potash,” became increasingly inadequate by the end of the 18th Century, and the search for commercially-viable routes to synthesizing soda ash from salt and other chemicals intensified.

Leblanc process:
In 1791, the French chemist Nicolas Leblanc patented a process for producing sodium carbonate from salt, sulfuric acid, limestone, and coal. First, sea salt (sodium chloride) was boiled in sulfuric acid to yield sodium sulfate and hydrogen chloride gas, according to the chemical equation

2 NaCl + H2SO4 ? Na2SO4 + 2 HCl
Next, the sodium sulfate was blended with crushed limestone (calcium carbonate) and coal, and the mixture was burnt, producing calcium sulfide.

Na2SO4 + CaCO3 + 2 C ? Na2CO3 + 2 CO2 + CaS
The sodium carbonate was extracted from the ashes with water, and then collected by allowing the water to evaporate.

The hydrochloric acid produced by the Leblanc process was a major source of air pollution, and the calcium sulfide byproduct also presented waste disposal issues. However, it remained the major production method for sodium carbonate until the late 1880s.

Solvay process
In 1861, the Belgian industrial chemist Ernest Solvay developed a method to convert sodium chloride to sodium carbonate using ammonia. The Solvay process centered around a large hollow tower. At the bottom, calcium carbonate (limestone) was heated to release carbon dioxide:

CaCO3 ? CaO + CO2
At the top, a concentrated solution of sodium chloride and ammonia entered the tower. As the carbon dioxide bubbled up through it, sodium bicarbonate precipitated:

NaCl + NH3 + CO2 + H2O ? NaHCO3 + NH4Cl
The sodium bicarbonate was then converted to sodium carbonate by heating it, releasing water and carbon dioxide:

2 NaHCO3 ? Na2CO3 + H2O + CO2
Meanwhile, the ammonia was regenerated from the ammonium chloride byproduct by treating it with the lime (calcium hydroxide) left over from carbon dioxide generation:

CaO + H2O ? Ca(OH)2
Ca(OH)2 + 2 NH4Cl ? CaCl2 + 2 NH3 + 2 H2O
Because the Solvay process recycled its ammonia, it consumed only brine and limestone, and had calcium chloride as its only waste product. This made it substantially more economical than the Leblanc process, and it soon came to dominate world sodium carbonate production. By 1900, 90% of sodium carbonate was produced by the Solvay process, and the last Leblanc process plant closed in the early 1920s.

Hou’s process
Developed by a Chinese chemist Hou Debang in 1930s. It is the same as the Solvay process in the first few steps. But, instead of treating the remaining solution with lime, carbon dioxide and ammonia is pumped into the solution, and sodium chloride is added until it is saturated at 40 °C. Then the solution is cooled down to 10 °C. Ammonium chloride precipitates and is removed by filtration, the solution is recycled to produce more sodium bicarbonate. Hou’s Process eliminates the production of calcium chloride and the byproduct ammonium chloride can be used as a fertilizer.
Internal: constipation, diuretic, Gulmanashak, colic, pain abdominal, worms intestinal, flatulence, eructations, abdominal winds, tympenitis, irritable bowel syndrome. External: promotes suppuration of boils, burns, pimples, leucoderma, white patches of skin.





Alum is a salt that in chemistry is a combination of an alkali metal, such as sodium, potassium, or ammonium and a trivalent metal, such as aluminum, iron, or chromium.

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It refers to a specific chemical compound and a class of chemical compounds. The specific compound is the hydrated aluminum potassium sulfate with the formula KAl(SO4)2.12H2O. The wider class of compounds known as alums have the related stoichiometry, AB(SO4)2.12H2O.

The most common form, potassium aluminum sulfate, or potash alum, is one form that has been used in food processing. Another, sodium aluminum sulfate, is an ingredient in commercially produced baking powder. (Have you never noticed the faint metallic taste in baking powder? It comes from the alum.)

The potassium-based alum has been used to produce crisp cucumber and watermelon-rind pickles as well as maraschino cherries, where the aluminum ions strengthen the fruits’ cell-wall pectins.

Alums are useful for a range of industrial processes. They are soluble in water; have an astringent, acid, and sweetish taste; react acid to litmus; and crystallize in regular octahedra. When heated they liquefy; and if the heating is continued, the water of crystallization is driven off, the salt froths and swells, and at last an amorphous powder remains.

Potassium alum is the common alum of commerce, although soda alum, ferric alum, and ammonium alum are manufactured.

Aluminium sulfate is sometimes called alum in informal contexts, but this usage is not regarded as technically correct. Its properties are quite different from those of the set of alums formally described above.

Early uses in industry:-
Alum was imported into England mainly from the Middle East, and, from the late 15th century onwards, the Papal States for hundreds of years. Its use there was as a dye-fixer (mordant) for wool (which was one of England’s primary industries), the value of which increased significantly if dyed. These sources were unreliable, however, and there was a push to develop a source in England especially as imports from the papal states were ceased following the excommunication of King Henry VIII. With state financing, attempts were made throughout the 16th century, but without success until early on in the 17th century. An industry was founded in Yorkshire to process the shale which contained the key ingredient, aluminium sulfate, and made an important contribution to the Industrial Revolution. Alum (known as turti in local Indian languages) was also used for water treatment by Indians for hundreds of years.

Current uses
Alum is used in vaccines as an adjuvant. Alum is commonly used as a coagulant in water treatment.


Alum from alunite
In order to obtain alum from alunite, it is calcined and then exposed to the action of air for a considerable time. During this exposure it is kept continually moistened with water, so that it ultimately falls to a very fine powder. This powder is then lixiviated with hot water, the liquor decanted, and the alum allowed to crystallize. The alum schists employed in the manufacture of alum are mixtures of iron pyrite, aluminium silicate and various bituminous substances, and are found in upper Bavaria, Bohemia, Belgium, and Scotland. These are either roasted or exposed to the weathering action of the air. In the roasting process, sulfuric acid is formed and acts on the clay to form aluminium sulfate, a similar condition of affairs being produced during weathering. The mass is now systematically extracted with water, and a solution of aluminium sulfate of specific gravity 1.16 is prepared. This solution is allowed to stand for some time (in order that any calcium sulfate and basic ferric sulfate may separate), and is then evaporated until ferrous sulfate crystallizes on cooling; it is then drawn off and evaporated until it attains a specific gravity of 1.40. It is now allowed to stand for some time, decanted from any sediment, and finally mixed with the calculated quantity of potassium sulfate (or if ammonium alum is required, with ammonium sulfate), well agitated, and the alum is thrown down as a finely-divided precipitate of alum meal. If much iron should be present in the shale then it is preferable to use potassium chloride in place of potassium sulfate.

Alum from clays or bauxite
In the preparation of alum from clays or from bauxite, the material is gently calcined, then mixed with sulfuric acid and heated gradually to boiling; it is allowed to stand for some time, the clear solution drawn off and mixed with acid potassium sulfate and allowed to crystallize. When cryolite is used for the preparation of alum, it is mixed with calcium carbonate and heated. By this means, sodium aluminate is formed; it is then extracted with water and precipitated either by sodium bicarbonate or by passing a current of carbon dioxide through the solution. The precipitate is then dissolved in sulfuric acid, the requisite amount of potassium sulfate added and the solution allowed to crystallize.

Types of alum:-

Soda alum
Sodium alum, Na2SO4·Al2(SO4)3·24H2O, mainly occurs in nature as the mineral mendozite. It is very soluble in water, and is extremely difficult to purify. In the preparation of this salt, it is preferable to mix the component solutions in the cold, and to evaporate them at a temperature not exceeding 60 °C. 100 parts of water dissolve 110 parts of sodium alum at 0 °C, and 51 parts at 16 °C. Soda alum is used in the acidulent of food as well as in the manufacture of baking powder.

Ammonium alum
Ammonia alum, NH4Al(SO4)2·12H2O, a white crystalline double sulfate of aluminium, is used in water purification, in vegetable glues, in porcelain cements, in natural deodorants (though potassium alum is more commonly used), in tanning, dyeing and in fireproofing textiles.

General Uses

*Alum in block form (usually potassium alum) is used as an aftershave, rubbed over the wet, freshly shaved face.
*Alum was used as a base in skin whiteners and treatments during the late 16th Century. A recipe for one such compound was given thus :
“For the Freckles which one getteth by the heat of the Sun: Take a little Allom beaten small, temper amonst it a well brayed white of an egg, put it on a milde fire, stirring it always about that it wax not hard, and when it casteth up the scum, then it is enough, wherewith anoint the Freckles the space of three dayes: if you will defend your self that you get no Freckles on the face, then anoint your face with the whites of eggs.” —Christopher Wirzung, General Practise of Physicke, 1654.

*Alum may be used in depilatory waxes used for the removal of body hair, or applied to freshly waxed skin as a soothing agent.
*In the 1950s, men sporting crewcut or flattop hairstyles sometimes applied alum to their front short hairs as an alternative to pomade. When the hair dried, it would stay up all day.
*Alum’s antibacterial properties contribute to its traditional use as an underarm deodorant. It has been used for this purpose in Europe; Mexico; Thailand, where it is called Sarn-Som; throughout Asia; and in the Philippines, where it is called Tawas. Today, potassium alum is sold commercially for this purpose as a “deodorant crystal,” often in a protective plastic case.

*Alum is used in vaccines as an adjuvant to enhance the body’s response to immunogens.
*Styptic pencils containing aluminium sulfate or potassium aluminium sulfateare are used as astringents to prevent bleeding from small shaving cuts.
*Alum in powder or crystal form, or in styptic pencils, is sometimes applied to cuts to prevent or treat infection.
*Powdered alum is commonly cited as a home remedy for canker sores.
*Preparations containing alum are used by pet owners to stem bleeding associated with animal injuries caused by improper nail clipping.


*Alum powder, found in the spice section of many grocery stores, may be used in pickling recipes and as a preservative to maintain fruit and vegetable crispness.
*Alum is used as the acidic component of some commercial baking powders.

As a Flame Retardant
Solutions containing alum may be used to treat cloth, wood and paper materials to increase their resistance to fire.
Alum is also a component of foamite, used in fire extinguishers to smother chemical and oil fires.

As a Chemical Flocculant
Alum is used to clarify water by catching the very fine suspended particles in a gel-like precipitate of aluminum hydroxide. This sinks to the bottom of the containing vessel and can be removed in a variety of ways.
Alum may be used to increase the viscosity of a ceramic glaze suspension; this makes the glaze more readily adherent and slows its rate of sedimentation.
Alum is an ingredient in some recipes for homemade modeling compounds intended for use by children. (These are often called “play clay” or “play dough” for their similarity to “Play-Doh”, a trademarked product marketed by American toy manufacturer Hasbro).

Related compounds
In addition to the alums, which are dodecahydrates, double sulfates and selenates of univalent and trivalent cations occur with other degrees of hydration. These materials may also be referred to as alums, including the undecahydrates such as mendozite and kalinite, hexahydrates such as guanidinium (CH6N3+) and dimethylammonium (CH3)2NH2+) “alums”, tetrahydrates such as goldichite, monohydrates such as thallium plutonium sulfate and anhydrous alums (yavapaiites). These classes include differing, but overlapping, combinations of ions.

A pseudo alum is a double sulfate of the typical formula ASO4·B2(SO4)3·22H2O, where A is a divalent metal ion, such as cobalt (wupatkiite), manganese (apjohnite), magnesium (pickingerite) or iron (halotrichite or feather alum), and B is a trivalent metal ion.

A Tutton salt is a double sulfate of the typical formula A2SO4·BSO4·6H2O, where A is a univalent cation, and B a divalent metal ion.

In popular culture
Gags in which someone ingests alum, either accidentally self-administered or surreptitiously administered by another, resulting in exaggerated effects, are a traditional staple of comedy. In live-action comedies, effects on the victim usually include extreme puckering of the mouth and lips and tightening of the throat. An example of this is in the Three Stooges short “No Census, No Feeling” when Curly is making a fruit punch and thinking it was sugar, puts alum in the fruit punch.

In animated cartoons, the effects are normally expanded to include extreme shrinking of the head. One example would be in the Merrie Melodies cartoon Long-Haired Hare featuring Bugs Bunny in which he plays a prank on a pompus opera singer named Giovanni Jones by lacing his atomizer with liquid alum. This causes Jones’ head to shrink and his voice to squeak. (Please see the link to the cartoon for a more complete synopsis.) Another such use is Back Alley Op-Roar (Freleng, 1945), in which Elmer feeds Sylvester Pussycat alum-laced milk, shrinking his head and driving his voice up several octaves while singing Figaro.

Also, Thomas Pynchon borrows the joke in chapter 16 of his 1963 novel V., in a scene where alum is slipped into the beer of a jazz trumpet player.