Soda Ash Dense is the industrial name of anhydrous sodium
carbonate. Sodium carbonate decahydrate, a colorless, transparent crystalline
compound, is commercially known as sal soda or washing soda. Soda Ash is
produced synthetically using the Ammonia Soda process (Solvay process) treating
sodium chloride with ammonia and carbon dioxide. Trona, a naturally occurring
mineral, is used also as a source of sodium carbonate. It is an essential
ingredient in many industrial and manufacturing processes, with widely
industrial uses, being crucial in the manufacture of flat and container glass
and a key ingredient in the production of detergents.
Sodium carbonate occurs in nature as Trona, trisodium
hydrogendicarbonate dihydrate (Na3HCO3CO3·2H2O).
Trona is also mined from some alkaline lakes by dredging. Hot saline springs
continuously replenish salt in the lake so that, provided the rate of dredging
is no greater than the replenishment rate, the source is fully sustainable.
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
NaCl + NH3 + CO2 +
H2O → NaHCO3 +
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 recycles its ammonia, it consumes
only brine and limestone, and has calcium chloride as its only waste product.
By 1900, 90% of sodium carbonate was produced by the Solvay process.
It is developed by Chinese chemist Hou Debang in 1930s. The
earlier steam reforming by-product carbon dioxide was pumped through a
saturated solution of sodium chloride and ammonia to produce sodium bicarbonate
via the following reactions:
NH3 + CO2 + H2O → NH4HCO3
NaCl → NH4Cl +
The sodium bicarbonate was collected as a precipitate due to its
low solubility and then heated to yield pure sodium carbonate similar to last
step of the Solvay process. More sodium chloride is added to the remaining
solution of ammonium and sodium chlorides; also more ammonia is pumped at
30-40°C to this solution. The solution temperature is then lowered to below
10°C. Solubility of ammonium chloride is higher than that of sodium chloride at
30°C and lower at 10°C. Due to this temperature dependent solubility difference
and the common-ion effect, ammonium chloride is precipitated in a sodium
The Chinese name of Hou's process (联合制碱法) means "Coupled
Manufacturing Alkali Method": Hou's process is coupled to the Haber
process and offers better atom economy by eliminating the production of calcium
chloride since ammonia no longer needs to be regenerated. The by-product
ammonium chloride can be sold as a fertilizer.
Domestically it is used as a water softener in laundry detergents.
Soda ash 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.
Medium dense or lighter grades of soda ash are typically used in detergents.
They function as a builder in the formulations of soaps, detergents and other
cleaning compounds, maximizing the dirt removal power of wash medium. Soda ash
also aids agglomeration, by carrying surfactants and provide the optimal pH for
Soda ash is an important component in a large number of formulated domestic
products, soaps, scouring powders, soaking and washing powders etc.