Their utility or importance in life depends
on their composition For example, the properties of
brass (mixture of copper and zinc) are quite different
from those of German silver (mixture of copper, zinc
and nickel) or bronze (mixture of copper and tin);
1 part per million (ppm) of fluoride ions in water
prevents tooth decay, while 1 5 ppm causes the tooth
to become mottled and high concentrations of fluoride
ions can be poisonous (for example, sodium fluoride is
used in rat poison); intravenous injections are always
dissolved in water containing salts at particular ionic
concentrations that match with blood plasma
concentrations and so on In this Unit, we will consider mostly liquid
solutions and their formation