Mary Lewonozgh, age 13, of Stratford, Conn,, for her questions

How is mercury mined and processed

Sometimes a thermometer breaks and we get a chance to see and handle this wonderful runny metal firsthand, But le t' s not do so without a word of warning. Liquid mercury gives off a little vapor, even at room temperatures. If inhaled for some time, this vapor can cause bodily injury. For this reason, we never leave mercury uncovered in a closet. It and its fumes should be stored in a closed container.

In pure form, the silvery, runny metal is rare in nature. We get it by extracting it from ores which contain mercury. Mankind has known how to do this for countless ages, Mercury was found among the treasures of Egypt's tombs, placed there more than 3,000 years ago. We know of a mercury mine in Spain which has been In operation since 800 B.C.

Mercury in sizeable amounts is present in some 25 different minerals. Only one of them, however, i s a useful mercury ore   a source from which we can extract it at a profits This ore is cinnabar, a red red earthy mineral. Cinnabar is mercuric sulphide, a compound of mercury and sulphu~. In processing the ore, the job is to separate the mercury from the sulphur,

This is done with heat for, like all elements, mercury and sulphur each have their own boiling points. Mercury boils and becomes vapor at 675 degrees Fahrenheit. Sulphur does not become vaporized below 832degrees, but it bursts into flame and becomes a brown paste at about 482 degrees. When roasted somewhat above 675 degrees, the cinnabar breaks apart into pasty sulphur and vaporized mercury,

The roasting may be done with blasts of hot air or the ore may be mixed with lime and heated in a furnace. In either case, the mercury rises as a vapor, The vapor is cooled and allowed to fall into long troughs of fine wet clay.

Now a drying agent, perhaps calcium chloride, is added to the clay and mercury mixture. The muddy batch 3s then squeezed until the pure mercury runs out. It is placed in 76 pound flasks and sent to market. Every year, the United States uses about 40,000 flasks of the silvery liquid  metal. In modern industry, we have about 3.,000 different uses for it.

Mercury is one of the basic chemical elements and it is 131 times heavier than water. It expands and contracts evenly when heated and cooled, This makes it a reliable substance to mark the thermometer degrees. Mercury vapor is used in ultra violet lamps. Various compounds of mercury are used to back mirrors, to make brilliant red paint, as disinfectants and in the manufacture of explosives and colored firecrackers. Mercury vapor and all its compounds, however, are poisonou,s and must be handled with care.