Mercury

an important metal. It is found in a pure state to some extent, but usually in combination with sulphur, from which it is separated by roasting. The ore, called cinnabar, is found chiefly in Austria, Spain, and California. It is noteworthy that the greatest American supply of mercury should have been discovered in California during the gold excitement at the very time and place it was most needed. Otherwise the miners would have been at the inconvenience and expense of obtaining mercury from far away Spain.

When cinnabar is roasted to a temperature of 357.25 deg. F., the mercury rises in a vapor and is caught and condensed. Ordinary mercury, or quicksilver, is a dense liquid, 13.6 times as heavy as water. It is sensitive to change of temperature and is much used in the construction of thermometers. It freezes at--39.5 deg. F. The union of mercury and any one of several metals is called an amalgam. Placer miners nail slats across their troughs or sluices, above which they pour a little mercury. The rolling grains of gold are heavy and are caught by the mercury, forming a gold amalgam from which the mercury is separated by heat and used again. Tin amalgam is used extensively in coating the backs of mirrors. Mercury is used in the manufacture of the explosive substances of gun caps.

In corrosive sublimate mercury is a rank poison. Calomel is a preparation of mercury much used in medicine. Mercury, taken in excess, remains in the system, enters the bones, and rots them. In the Austrian cinnabar mines the extreme limit of life is six years. It is said the bones of the skeletons of the miners are so loaded with mercury that quicksilver can be shaken from them.

One of the most noted uses of mercury is its employment in the making of barometers. Under ordinary conditions, a thirty-inch column of mercury at the sea level is about as heavy as a similar column of air extending to the upper limits of the atmosphere.

Producers put up mercury for sale usually in flasks of seventy-six and one half pounds. About 100,000 flasks are produced yearly, of which, roughly speaking, Spain furnishes a half, the United States a fourth, Austria and Italy the remainder.

See Placer Mining; Barometer