Civil Engineering Reference
In-Depth Information
Arsenic
Arsenic is usually produced from arsenopyrite (FeAsS). Its main use is in timber
impregnation, where it is mixed with copper or chrome. Accessible sources of
arsenic are very limited. Arsenic has been the most popular poison used for mur-
der for many centuries! The metal has a tendency to biological amplification and
is extremely toxic.
Magnesium
Magnesium is not used very much. It is a light metal which in many ways can
replace aluminium. It is extracted from dolomite and sea-water and is thus the
only metal with large accessible reserves. Magnesium is not considered toxic.
Titanium
Titanium is the tenth most common element in the Earth's crust, even if the
accessible reserves are very few. The metal has been given a positive prognosis
as extraction costs for the other metals are increasing, but it is relatively difficult
to extract and requires high energy levels to do so. Titanium dioxide is produced
from ore of ilmenite (FeTiO
3
), and 92 per cent is used as the pigment titanium
white, usually for paints and plastics. Production of titanium oxide is highly pol-
luting, whereas the finished article causes no problems.
Cobalt
Cobalt is a metal used as a pigment and drying agent in the painting industry
and also as an important part of various steel alloys. Cobalt is slightly poisonous
for plants, but very little is known about how it affects organisms in water.
Gold
Gold has a very limited use in the building industry. The most important use is
the application of a thin layer on windows to restrict the amount of sun and
warmth coming into a building, and to colour glass used for lanterns in yellow
and red. Of the 80 000 tons of gold calculated to have been mined since the begin-
ning of its use, most is still around, partly because gold does not oxidize or break
down and partly because of its value. The gold used in window construction is
considered to be taken out of circulation, but this only represents a small
quantity.
Non-metallic minerals
The most important non-metallic minerals in the building industry are lime and
silicious acid.
