The document discusses fertilizers and their production. It states that fertilizers are chemicals or mixtures added to soil to overcome deficiencies in nutrients like nitrogen (N), phosphorus (P), and potassium (K). There are three main types of fertilizers: nitrogenous, phosphatic, and potassic. A complete fertilizer contains all three nutrients. The document then provides details on the production of urea and sodium hydroxide via specific chemical processes.

1. Chemical
Manufactures

2. Fertilizers
FERTILIZERS
Compounds or mixture of chemicals which are added to the soils in order to overcome
deficiency of minerals are called as fertilizers. N, P and K are three important critical elements
which are depleted from the field and need to be replenished periodically.
Deficiency caused by a critical element (N, P or K) is called Primary Deficiency.
Fertilizers are the chemicals or mixtures of chemicals which are added to the soil to overcome
the deficiency of these minerals. There are three types of fertilizers:
Nitrogenous fertilizers: They supply nitrogen to the soil, e.g., sodium nitrate, ammonium
sulphate, ammonium nitrate, ammonium chloride and urea.
Phosphatic fertilizers: They supply phosphorus to the soil, e.g., superphosphate, triple super-
phosphate, bone meal, and rock phosphate.
Potassic fertilizers: They supply potassium to the soil, e.g potassium chloride, potassium
nitrate etc..
Mixture containing all the three principal nutrients, N, P and K, are called complete fertilizer or
NPK.

3. Production of urea:
Principle: Ammonia and carbon dioxide are compressed and reacted in
reactor at high temperature (180-210℃) and high pressure (150 atm)
whereby ammonia carbamate is formed:
NH3 + CO2 NH2COONH4 + Heat
Then, Ammonium carbamate is decomposed to give urea and urea
solution is evaporated up to dryness to make granules of urea.
NH2COONH4 + heat NH2CONH2 + H2O.

5. Manufacture of Sodium Hydroxide by
Diaphragm Cell
Sodium hydroxide is manufactured by the electrolysis of brine in
which diaphragm cell is preferred over mercury cathode cells due
to its higher efficiency and the absence of health hazards
associated with mercury.
A diaphragm cell typically consists of a porous barrier (the
diaphragm) made of materials like asbestos which separate the
anode and cathode compartments.
.

6. Principle
↪ Brine is an aqueous solution of NaCl
i.e., NaCl(aq) → Na+(aq) + Cl-(aq)
↪ The following electrolytic reaction occurs in electrolysis of brine.
↪ At anode: Cl- is oxidized to chlorine gas as
2Cl- + 2e- → Cl2(g)
↪ At cathode: Water molecules undergo reduction to hydrogen gas
leaving OH- ion in the solution as,
2H2O + 2e- → H2(g) + 2OH-
↪ The overall cell reaction is
2NaCl(aq) + 2H2O(l) → H2(g) + Cl2(g) + 2NaOH(aq)

7. Side reactions
Side reactions are undesirable reactions which may occur in small extent if
the products are not prevented from mixing in the plant.
In order to minimize the side reactions and to get pure NaOH, Diaphragm cell
is devised. Nelson first of all introduced this cell which is known as Nelson's .

9. When saturated brine solution is passed through anode Compartment
Chlorine gas is collected at the anode and H2 gas is collected at cathode
compartment
It consists of a perforated Steel cathode line with asbestos. the anode consist
of graphite rod diping in sodium chloride solution i.e saturated brine solution
and separated From the cathode by asbestos lining
On passing the current, chlorine is evolved at anode. The sodium Ion passes
through the asbestos and changes to sodium atom at the cathode. It reacts
with steam to form caustic soda(NaOH) solution which is collected at the
bottom of the tank and is drawn out from times to time and concentrated.

10. The mixture produced at the cathode compartment after the
electrolysis of saturated brine contains 12% NaOH and 16% NaCl in
aqueous solution.
In this process about 50% of the NaCl is converted to NaOH by electrolysis.
The resulting mixture is transferred in another tank where NaOH is
concentrated to about 50% by heating with steam.
Almost all NaCl crystallizes out and it is re-used. The resulting 50% NaOH
contains about 1% NaCl. For industrial use, 50% aqueous NaOH, no harm
with 1% NaCl, is supplied rather than its solid form.
For small scale use solid form is supplied.

12. Manufacture of Na2CO3 by Solvay or
Ammonia Soda Process
Principle
When carbon dioxide gas is bubbled into pure brine solution (28%
NaCl) saturated with ammonia, ammonium bicarbonate is formed in
cold which reacts immediately with sodium chloride to form sodium
bicarbonate and ammonium chloride.
Sodium Bicarbonate precipitates from the mixture and is separated
from ammonium chloride from filtration. Solid sodium bicarbonate
when calcined gives sodium carbonate.

13. In this process, ammonia is converted into ammonium carbonate
which then converted to ammonium bicarbonate by passing excess
carbon dioxide in a sodium chloride solution saturated with ammonia.
2NH3+H2O+CO2→(NH4)2CO3
(NH4)2CO3+H2O+CO2→2NH4HCO3
The ammonium bicarbonate thus formed reacts with the sodium
chloride to give sodium bicarbonate and ammonium chloride.
NH4HCO3+NaCl→NH4Cl+NaHCO3
As sodium bicarbonate has poor solubility, it gets prepicitated. The
sodium bicarbonate is isolated and is heated to give sodium
carbonate.
2NaHCO3→Na2CO3+CO2+H2O

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