Phosphoric acid, also known as
orthophosphoric acid, is the most important oxygen acid of phosphorus with the
chemical formula H3PO4. It is also the most common orthophosphoric acid. Pure
form of phosphoric acid is a crystalline solid with a 42.35°C melting point.
Its gravity is 1.834 at the temperature of 18°C and soluble in water and
alcohol. It is a colorless, syrupy liquid form in less concentrated form. It
can also combine with them to form a range of compounds that are also referred
to as phosphoric acids.
Phosphoric acid is
usually produced by three commercial methods, including wet process, thermal
process and dry kiln process. Among these three methods, wet process is the
most common route. The phosphate first reacts with the recycled phosphoric acid
from the process and then mixed with sulfuric acid as a leaching agent. Then
after the evaporator condensate, the gypsum separates with phosphoric acid and
obtains the product acid.
acid is applied as a "rust converter", by direct application to rusted
iron, steel tools, or surfaces. The phosphoric acid will transform
reddish-brown iron(III) oxide, Fe2O3 (rust) to black ferric phosphate,
FePO4. "Rust converter" is in a form of a greenish liquid, but it is
more often formulated as a gel, usually called "naval jelly". Sometimes,
it is sold in other names, such as "rust remover" or "rust killer". As a
thick gel, it is applied to sloping, vertical, or even overhead
It is used to produce hydrogen
halide by reacting it with halide. Phosphoric acid find important place as
electrolyte in phosphoric acid fuel cells, oxy-hydrogen generators and Copper
electro polishing. It is used as a wet etching agent for making impressions on
surface. Most of the industries using iron and steel use phosphoric acid as a
rust converter thanks to its ability to transform reddish-brown iron(III)
oxide, Fe2O3(rust) to black ferric phosphate, FePO4.
Used as reaction fertilizer in the
soil around a granule acidification is generated that improves the utilization
of phosphorus applied and available in the rhizosphere. Due to its nitrogen
content (present as ammonia), it is good for crops that require these nutrients
in its initial phase.