Inorganic Chemicals - Fundamentals of Industrial Chemistry: Pharmaceuticals, Polymers, and Business - page 10

hydroxide (Ca(OH) 2 ), also known as slaked lime or hydrated lime, is formed.
Calcium hydroxide has low water solubility (0.16 g/100 g water at 25 ∘ C) [15]
and a suspension in water is called “milk of lime.”
2.4 SODA ASH
Soda ash is sodium carbonate (Na 2 CO 3 ) and is a major chemical with about
11 million metric tons being produced each year in the United States [16].
About half of the produced soda ash is used in glass manufacture. Chemi-
cal manufacture is the second major use followed by soaps and detergents.
Soda ash is traditionally produced from trona ore in the USA, and most of the
soda ash production in the United States comes from Wyoming, which has
the largest known trona ore deposit in the world [17]. Trona(sodium sesqui-
carbonate dihydrate, Na 2 CO 3 ⋅ NaHCO 3 ⋅ 2H 2 O) is a complex salt of sodium
carbonate and sodium bicarbonate (NaHCO 3 ). Trona is converted to soda ash
by calcination, followed by dissolution, filtration to remove insolubles, and
crystallization of the monohydrate. After isolation, the hydrate is heated to
remove water.
2.5 TITANIUM DIOXIDE
Titanium dioxide (TiO 2 ), also called titania, has excellent light-scattering
properties and because of this, has found wide use as a white pigment. U.S.
production of titanium dioxide is estimated at about 300,000 metric tons
per year with another 1.1 million metric tons being imported [18]. Titanium
is the ninth most abundant element in the earth's crust. Of the 83 elements
found in nature, 12 make up 99.7 percent of the Earth's crust. In decreasing
order of natural abundance they are: oxygen, silicon, aluminum, iron,
calcium, magnesium, sodium, potassium, titanium, hydrogen, phosphorus,
and manganese [19]. The main titanium ores are ilmenite (FeTiO 3 )and
rutile (TiO 2 ). Titanium ore is converted to pure titanium dioxide, a white
crystalline powder.
Titanium dioxide imparts whiteness and brightness to objects. It makes
paints, plastics, paper and even food white in color. It also imparts opacity,
making objects and coatings less transparent. The major use is in paints
and coatings. It imparts whiteness in white paints but even color paints use
titanium dioxide to give hiding power. Paints without titanium dioxide are
more “see through.” Other major uses include plastics and paper, but tita-
nium dioxide has widespread application including cosmetics, sunblock, and
toothpaste.