Stories About Chemistry
27. Liquid Metals and a
Gaseous (?) Metal
All the metals are solids, harder or softer. Such is the general rule. But there are exceptions.
Some metals are more like liquids. A chip of gallium or cesium melts on your palm, because the melting point of these metals is just below thirty degrees Celsius (86°F). Francium, which has not been prepared as the pure metal so far, would melt at room temperature.
Mercury is a classical example of a liquid metal which everybody knows. It freezes at minus 39°C (-38.2°F), which makes it eligible for various kinds of thermometers.
An important rival to mercury in this respect is gallium, and here is why. Mercury boils at the comparatively low temperature of about 300°C (572°F). This makes mercury thermometers useless for measuring high temperatures. But it takes a temperature of 2000°C (3670°F) to turn gallium into a vapour.
Not a single metal can remain in the liquid state for so long, i.e., has such a large interval between its melting and boiling points, as gallium. This makes gallium an excellent material for high-temperature thermometers.
One more thing, and this is quite remarkable. Scientists have proved theoretically that if there existed a heavy analogue of mercury (an element with a very large atomic number an inhabitant of, the imaginary seventh floor - eighth period - of the Big House, unknown on Earth) its natural state at ordinary conditions would be gaseous.
A gas possessing the chemical properties of a metal!
Will scientists ever have such a unique element to study?
A lead wire can be melted in a match flame. Tinfoil immediately changes into a drop of liquid tin if thrown into a fire. But to liquefy tungsten, tantalum or rhenium, the temperature has to be raised above 3000°C (about 5500°F).
These metals are harder to melt than any of the others. That is why the filaments of incandescent electric light bulbs are made of tungsten and rhenium.
The boiling point of some metals are really tremendous. For instance, hafnium begins to boil at 5400° (almost 9800° F) (!), almost the temperature of the Sun’s surface.