CHAPTER IX

CARBON

(Carbon = C)

Introduction. Carbon, though perhaps not known by that name, in some form is known to all of us. We are all familiar with the black soot which collects on the side of a lamp-chimney from the burning of an unevenly trimmed lamp wick. To this substance the name lampblack is given.

All have seen the charred remains of bones that have been roasted out of reach of air. This substance we know as bone black. Charcoal, too, is somewhat familiar from its use in filtering water or as a deodorizer, while coke and coal are known as our chief sources of fuel for heating purposes. The so-called lead of the lead pencil is graphite, a form of carbon, while the diamond is another form.

As widely as these substances vary in physical properties, yet each is chiefly carbon. Carbon is the most widely distributed of all the known elements. It is found in all living matter, whether plant or animal, and it also forms a considerable part of the earth's crust. In the uncombined or free state it is found as diamond, coal, and graphite.

Charcoal. If a piece of charcoal is examined carefully it will be seen to look very much like a small block of wood. And such, in fact, it is. It is usually made by heaping up the small blocks of wood into mounds and covering the whole with soil and turf to exclude the air. Then a fire is started underneath the wood and although some of the wood burns, yet the greater portion only smolders. The result is that all other substances are driven off, leaving practically pure carbon. A more modern method of producing charcoal is to heat wood in closed iron ovens. The principle involved in either case is the same; namely, to break down the compounds which comprise wood into simpler substances, and drive off all but carbon. Animal carbon is prepared by burning bones away from air.

Uses of charcoal. Because of its porous nature, charcoal is a great absorber of gases. This quality renders it of great value in contributing to our comfort and welfare. The unpleasant odors which arise from sewers can be prevented by suspending bags of charcoal in the man-holes. Cistern water is kept sweet and clean by filtering through charcoal. In many

homes in our cities all water used for drinking and cooking purposes is passed through charcoal filters. In passing through the porous charcoal the impurities are removed. However, unless the filter is cleaned frequently it may become a menace to health rather than a benefit. The pores in the filter become clogged

with impurities and furnish a

germs may find their way there.

hotbed for whatever

So, instead of remov

ing the things that are injurious, it may be the means of supplying them. The necessity of keeping the filter thoroughly cleaned must be clear to all.

For this

Charcoal is also used as a decolorizer. purpose, however, animal charcoal is chiefly used. If you have ever visited a sugar beet factory, no doubt you were impressed by the difference of color in the dark sap from which the sugar is made and the beautiful white crystals of commercial sugar. This transformation in color is brought about in the large filters, called charfilters, which contain this finely divided charcoal through which the syrup passes. Large quantities of charcoal are used in sugar refining.

Lampblack. Lampblack or soot is practically pure carbon. It is obtained by incomplete burning; that is, by burning with a limited supply of air. This can be shown by cutting off the air to your Bunsen flame and holding a white porcelain plate over the flame. The soot will collect on the plate. This finely divided black powder furnishes the pigment for the manufacture of printer's ink and paint.

Coal. Generally speaking, coal is divided into soft, or bituminous, and hard, or anthracite coal. The difference is greater than the mere physical difference of degrees of hardness and is explained by the greater percentage of carbon found in the hard coal. Anthra

cite coal generally consists of about 95% carbon while bituminous coal contains 80% or less of carbon.

Copyright by Underwood & Underwood, N. Y.

Fig. 27. Mining anthracite coal three miles underground. Coal is wood that has undergone great changes during past centuries. The harder the coal the longer this change has been taking place. During a period of the earth's history known as the Carboniferous Age, the earth was covered with a luxurious growth

of vegetation under swamp and marsh conditions. As this fell and accumulated year after year, and century after century, and became submerged, many of the more volatile gases were driven off, with some of the carbon, no doubt, but much of the carbon was preserved. As the pressure of the accumulating weight increased, further changes took place until eventually coal, our chief source of heating fuel, was produced.

Copyright by Underwood & Underwood, N. Y. Fig. 28. Cutting peat in Ireland, where it is used as a substitute for coal.

Successive stages in coal formation are wood, peat, lignite or brown coal, soft or bituminous coal, and hard or anthracite coal.

Coke is produced from coal in very much the same manner that charcoal is produced from wood. When