Each metal actually has its own particular hue. Its dark, dull, or silvery base always has a definite tint. Scientists have become convinced of this by studying metals in the very pure state.

   Many of them when left in the air, become coated sooner or later with a very thin film of oxide which masks their true colour. But the pure metals give a very wide range of colours. The observant eye can discern metals with bluish, greenish-blue and greenish shades, with a reddish or yellowish play of colours, dark-grey like sea water on a cloudy autumn day, and shiny silvery ones which reflect solar rays like a mirror.

   The colour of a metal depends on many factors. Among others, it depends upon the method of its production. A metal obtained by sintering has a different appearance from the same metal poured into an ingot.

   If we compare metals by weight, we can distinguish light, medium and heavy ones.

   These "weight classes" have their record holders.

   Lithium, sodium, and potassium do not sink in water, because they are lighter than water. For example, the density of lithium is almost half that of water, which equals unity. Were lithium not so active an element, it would be an excellent material for a great variety of purposes. Imagine a ship or an automobile made entirely of lithium. Unfortunately, chemistry bans this attractive idea.

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