Methods of production of washing soda; baking soda, bleaching powder

Methods of production and manufacturing

Washing soda

The chemical name of washing soda is sodium carbonate decahydrate, and its chemical formula is Na2CO3.10H2O. So washing soda is hydrated salt of sodium carbonate containing 10 molecules of water of crystallization. Sodium carbonate is manufactured by Solvay process.

The manufacture of sodium carbonate by Solvay process includes following steps:

Saturation of Sodium Chloride with Ammonia        

First of all a cold and concentrated solution of sodium chloride called brine is saturated with ammonia to get a solution called ammoniacal brine.


In the second step the ammoniacal brine prepared in first step is dropped from the top of a tower called carbonating tower and carbon dioxide gas is passed into the tower from near its base. The carbonating tower has partitions which are made up of iron plates with hole in the center and covered with perforated plate. The function of these partitions is to slow down the down coming ammoniacal brine solution so that the upcoming carbon dioxide has enough time to react with it completely.

So as the ammoniacal brine comes down from the top of the carbonating tower, it reacts with carbon dioxide to form precipitates of sodium hydrogencarbonate (also called sodium bicarbonate):

NaCL + NH3 + CO2 + H2O = NaHCO3 + NH4CL


Baking soda:production and Manufacturing

Baking Soda, a sodium bicarbonate, is a naturally occurring substance that is present in all living things–it helps living things maintain the pH balance necessary for life. Baking Soda is made from soda ash, also known as sodium carbonate. The soda ash is obtained in one of two ways: it can be manufactured by passing carbon dioxide and ammonia through a concentrated solution of sodium chloride (table salt). In our case, it is mined in the form of an ore called trona. Whether the soda ash is mined or processed, it is dissolved into a solution through which carbon dioxide is bubbled, and sodium bicarbonate precipitates out, forming ‘Pure, Safe and Natural” Baking Soda.

Steps of manufacturing

  • Soda ash can be manufactured chemically using the Solvay process, or it can be made from trona ore. If trona ore is used, it must first be mined. After it has been brought to the surface, the trona ore is transported to a variety of processing plants. There, the ore is refined into a slurry of sodium sesquicarbonate, an intermediate soda ash product that actually contains both soda ash (sodium carbonate) and baking soda.
  • the intermediate soda ash solution is put into a centrifuge, which separates the liquid from the crystals. The crystals are then dissolved in a bicarbonate solution (a soda ash solution made by the manufacturer) in a rotary dissolver, thereby becoming a saturated solution. This solution is filtered to remove any non-soluble materials and is then pumped through a feed tank to the top of a carbonating tower.
  • Purified carbon dioxide is introduced into the bottom of the tower and held under pressure. As the saturated sodium solution moves through the tower, it cools and reacts with the carbon dioxide to form sodium bicarbonate crystals. These crystals are collected at the bottom of the tower and transferred to another centrifuge, where excess solution (filtrate) is filtered out. The crystals are then washed in a bicarbonate solution, forming a cake-like substance ready for drying. The filtrate that is removed from the centrifuge is recycled to the rotary dissolver, where it is used to saturate more intermediate soda ash crystals.
  • The washed filter cake is then dried on either a continuous belt conveyor or in a vertical tube drier called a flash dryer. The theoretical yield from the process, according to the Church & Dwight Company, is between 90 and 95 percent, and the baking soda manufactured is more than 99 percent pure.

production of bleaching powder

Calcium hypochlorite is an inorganic compound with formula Ca(ClO)2. It is the main active ingredient of commercial products called bleaching powder, chlorine powder, or chlorinated lime, used for water treatment and as a bleaching agents. This compound is relatively stable and has greater available chlorine than sodium hypochlorite (liquid bleach). It is a white solid, although commercial samples appear yellow. It strongly smells of chlorine, owing to its slow decomposition in moist air. It is not highly soluble in hard water, and is more preferably used in soft to medium-hard water. It has two forms: dry (anhydrous); and hydrated (hydrous).

Calcium hypochlorite is produced industrially by treating lime (Ca(OH)2) with chlorine gas. The reaction can be conducted in stages to give various compositions, each with different concentration of calcium hypochlorite, together with unconverted lime and calcium chloride.

2 Cl 2 + 2 Ca(OH) 2 → Ca(OCl) 2 + CaCl 2 + 2 H 2O

Bleaching powder is made with slightly moist slaked lime. It is not a simple mixture of calcium hypochlorite, calcium chloride, and calcium hydroxide. Instead, it is a mixture consisting principally of calcium hypochlorite Ca(OCl)2, dibasic calcium hypochlorite, Ca3(OCl)2(OH)4, and dibasic calcium chloride, Ca3Cl2(OH)4.

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