James Roeder, Age 11, Of Wichita, Kan., for his question:
What makes asbestos fireproof?
Most of the earth's rocky minerals ccme in bumpy lumps or smooth faced crystals. Asbestos is a mineral made from fine silken threads, closely packed or matted together. Industry has 3000 jobs for asbestos, and there is more work for this marvel of minerals in the conquest of space.
In the dim past, the bodies of eastern princes were burned in sheets of fireproof asbestos to preserve all the human ashes from the cinders. The eternal tapers on the altars of ancient rome had wicks of fireproof asbestos. The globe trotting reporter marco polo probed the legend of the salamander that was supposed to spring back to life after being consumed by a flaming fire. The so called salamander hair, he found, actually was the silken thread of the mineral asbestos.
The fireproof qualities of this marvel of minerals have been known and used since ancient times. The explanation of this mysterious quality had to wait for the modern age of chemistry. When a substance burns, it combines with oxygen and its molecules are broken apart and become atoms and molecules of different substances. Oxygen is necessary for the burning process, which is why the chemist calls all forms of burning oxidation.
If there is no oxygen among the chemicals, there can be no fire. This is why a fire cannot burn in an atmosphere composed entirely of carbon dioxide, and a blanket of carbon dioxide sometimes is used as a fire extinguisher. It deprives the blaze of the free oxygen it needs to keep going. There also is oxygen to aid the blaze, either free or in some compounds, in wood and coal and in most other natural substances.
There also is oxygen in asbestos, for it is a silicate compound of the elements silicon and oxygen. But this oxygen cannot be freed from its molecules. This fibrous mineral is fully oxidized, and there is absolutely no oxygen available to fuel the burning process. Asbestos cannot, just cannot burn. Under high temperatures it simply melts and decomposes. Glass, which is a man made compound of silicon, also is fully oxidized. Glass refuses to burn in the flames for the same reason that asbestos cannot be burned.
Asbestos has another quality that makes it a priceless firefighter. It is a good insulator, very slow to conduct heat through its silky threads. An asbestos suit protects a fireman from both the flames and the heat, for only the surface facing the fire gets hot.
It seems miraculous that nature prepared this fireproof mineral in threads of yarn. Its silken fibers can be woven into fireproof fabrics or matted with gypsum or other minerals to make fireproof tiles and slabs of fireproof board. An italian scientist once suggested that paper money should be made from asbestos, and if his idea had been followed we would never have to worry about burning up our dollars.