A bluish-white, lustrous, metallic element in group IIB of the periodic table;
zinc is an anomalous transition element.
It occurs naturally as sphalerite, smithsonite, hemimorphite, and wurtzite,
and is extracted by roasting to the oxide and reduction with carbon. Zinc is brittle at room temperatures
but malleable when heated. It is used to form a wide variety of alloys including brass, bronze,
German silver, various solders, and nickel silver, in galvanizing iron and other metals, for electric fuses, anodes,
and meter cases, and in roofing, gutters, and various household objects.
Zinc is a vital trace element, occurring
in erythrocytes (red blood cells) and insulin.
|The Imperial smelting process involves the simultaneous production of zinc and lead from a blast furnace. This is of particular value as the two metals frequently occur together in nature as a mixture of lead and zinc sulfides.
1) zinc and lead concentrates for sintering
2) sintering plant
3) air is blown up through the sintering bed to convert the zinc and lead sulfides to their oxides with volatization of sulfur dioxide gas
4) sulfur dioxide removed and used for sulfuric acid manufacture
6) coke preheater
7) furnace charge of hot coke, lead and zinc sinter
8) blast furnace
9) zinc vapor and blast furnace gases
10) addition of sulfur to promote slag
11) slag containing copper sulfide and copper arsenide, removed for copper refining
12) lead bullion, containing impurities of gold, silver, tin, bismuth, and cadium
13) electrolytic process for lead refining
14) impurities removed for separate refining
15) 99.9% lead
16) lead splash condenser. Zinc vapor is condensed by shock cooling with molten lead
17) furnace gasses removed
18) zinc/lead separation system by cooling
19) 99.9% zinc
Chemically zinc is reactive, readily forming divalent ionic salts (Zn2+),
and zincates (ZnO22-) in alkaline solution; it forms
many stable ligand complexes. Zinc chloride
is used as a flux, for fireproofing, in dentistry, and in the manufacture
of batteries and fungicides. Zinc oxide and sulfide are used as white pigments.
Additionally, zinc oxide is an ingredient of many skin preparations that
has a mild astringent (dying) action
and a soothing effect. Zinc oxide is used to treat painful, itchy, and moist
skin (such as eczema, bedsores, and diaper rash). It also blocks the ultraviolet
rays of the sun.
|relative atomic mass
||7.14 (at 25°C)
Zinc and health
Zinc is a trace element (second only
to iron in its concentration in the body) that is essential for normal growth,
development of the reproductive organs, normal function of the prostate
gland, healing of wounds, and the manufacture of proteins and nucleic acid. Zinc is a cofactor that controls the activities of more than 100 enzymes and is involved in the functioning of the hormone insulin.
Small amounts of the element are present in a wide variety of foods; particularly
rich sources include lean meat, wholemeal breads, whole grain cereals, dried
beans, and seafoods. Beef, pork, and lamb contain more zinc than fish. The
dark meat of a chicken has more zinc than the light meat.
Zinc deficiency is rare, most cases occurring in people who are generally
malnourished. Deficiency may also be caused by any disorder that causes
malabsorption, by acrodermatitis enteropathica (a disorder of zinc absorption),
or by increased zinc requirements due to cell damage (for example, as a
result of a burn or in sickle cell
anemia). Symptoms of deficiency include impairment of taste and loss of appetite; in severe cases, there may also be hair loss and inflammation
of the skin, mouth, tongue, and eyelids.
Prolonged, excessive intake of zinc (usually through supplements) may interfere
with the intestinal absorption of iron and copper, leading to a deficiency
of these minerals and resultant symptoms of nausea, vomiting, fever, headache, tiredness, and abdominal pain.