Inorganic Chemicals - Fundamentals of Industrial Chemistry: Pharmaceuticals, Polymers, and Business - page 7

224 pounds of sulfuric acid every year. The actual amount used is about 20%
higher because of imports.
Reagent sulfuric acid is 95 - 98% by weight sulfuric acid with the
remainder being water. It is a clear, colorless, oily, corrosive liquid. Fuming
sulfuric acid, also known as oleum, is sulfuric acid with dissolved sulfur
trioxide. Oleum is sold at a variety of percentages that indicate the amount
of sulfur trioxide. For example, 24% oleum is 24 g sulfur trioxide per 100 g
total. Recognize that this is also true for other mass units. So 24% oleum is
also 24 pounds sulfur trioxide per 100 pounds total or 24 tons sulfur trioxide
per 100 tons total. This is also sometimes expressed as 105.4% H 2 SO 4 ,
because 100 g of 24% oleum can make 105.4 g H 2 SO 4 when the oleum reacts
with water. This is a theoretical exercise and generally should not actually be
done because oleum reacts violently with water. It is worthwhile to review
the arithmetic because such exercises commonly need to be done in industry.
The calculation can be done by converting the grams of sulfur trioxide per
100g total to moles of sulfur trioxide, multiplying by 18 g per mole of water,
and adding that number to 100. The calculation is demonstrated for 34%
oleum, which can be called 107.65% H 2 SO 4 .

1moleSO 3
80 g

1moleH 2 O 18 g

1moleH 2 O =

34gSO 3 × ×

1moleSO 3 ×

7 . 65gH 2 O

Sulfuric acid has many uses but one of the largest uses is for fertilizer man-
ufacture. Primary nutrients for plants are nitrogen, phosphorus and potassium.
The major use of sulfuric acid in fertilizer manufacture is in the production
of phosphoric acid, which in turn is used to produce phosphorus-containing
fertilizers.

2.2 PHOSPHORIC ACID

A major use of sulfuric acid is in the manufacture of phosphoric acid (H 3 PO 4 ),
also known as orthophosphoric acid. The principle use of phosphoric acid is
to make fertilizers. In the United States, phosphate rock ore is mined by six
companies at 12 mines and upgraded to 28 million metric tons [8]. Most of the
mining is done in Florida and North Carolina. China is the leading producer
of phosphate rock with 72 million metric tons of the 191 million metric tons
manufactured worldwide.
Phosphorus is an essential element for plant and animal nutrition and
phosphate rock is the only significant resource of phosphorus [9]. Phosphate
rock is converted into phosphoric acid, which in turn is converted into
phosphorus fertilizers. Common examples of phosphorous-containing fer-
tilizers are triple superphosphate, monoammonium phosphate, diammonium