Page 118 - Chemical and process design handbook

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AMMONIUM SULFATE

Ammonium sulfate [(NH ) SO , density: 1.769] is a colorless crystalline
4 2 4
solid that decomposes above 513°C and is soluble in water but insoluble in
alcohol.
Ammonium sulfate was originally manufactured by using sulfuric acid
to scrub by-product ammonia from coke-oven gas, and much is still pro-
duced in this manner. Most of the ammonium sulfate produced is now
made by reaction between synthetic ammonia and sulfuric acid.
2NH + H SO → (NH ) SO
3 2 4 4 2 4
Where sulfur for sulfuric acid is at a premium, a process based on gyp-
sum and carbon dioxide from combustion can be used:

(NH ) CO + CaSO 2H O → CaCO + 2H O + (NH ) SO
4 2 3 4 2 3 2 4 2 4
Water is removed by evaporation, and the product is crystallized to
o
large, white uniform crystals, melting point 513 C, with decomposition.
Anhydrite (CaSO ) can also be used in this process.
4
Large quantities of ammonium sulfate are produced by a variety of indus-
trial neutralization operations required for alleviation of stream pollution by
free sulfuric acid (H SO ) as well as in the manufacture of caprolactam.
2 4
Ammonium sulfate also is a byproduct of coke oven operations where the
excess ammonia formed is neutralized with sulfuric acid to form the ammo-
nium sulfate.
Ammonium sulfate is used predominantly as a fertilizer. As a fertilizer,
(NH ) SO has the advantage of adding sulfur to the soil as well as nitro-
4 2 4
gen, as it contains 21% by weight nitrogen and 24% by weight sulfur.
Ammonium sulfate also is used in electric dry cell batteries, as a soldering
liquid, as a fire retardant for fabrics and other products, and as a source of
certain ammonium chemicals. Other uses include water treatment, fer-
mentation processes, fireproofing agents, and leather tanning.

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