CARBON AND THE II YDROCA !{!',< ).\s 327 



tju.-intity of carbon which enters into combination in molecules of its 

 compounds ; but the weight of the molecules of charcoal is probably 

 very great. This weight remains unknown, because charcoal is capable 

 of but few direct reactions, and those only at a high temperature (when 

 the weight of its molecules probably changes, as when ozone changes into 

 oxygen), when it does not turn into vapour. Carbon exists in nature, 

 both in a free and combined state, in most varied forms and aspects. 

 Carbon in a free state is found in at least three different forms, as 

 charcoal, graphite, and the diamond. In a combined state it enters 

 into the composition of what are called organic substances a 

 multitude of substances which are found in all plants and animals. It 

 exists as carbonic anhydride both in air and in water, and in the soil 

 and crust of the earth as salts of carbonic acid and as organic remains 

 The variety of the substances of which the structure of plants and 

 animals is built up is familiar to all. Wax, oil, turpentine, and tar, 

 cotton and albumin, the tissue of plants and the muscular fibre of 

 animals, vinegar and starch, are all vegetable and animal matters, and 

 all carbon compounds. 1 The sphere of carbon compounds is so vast 



1 Wood is the non- vital part of ligneous plants ; the vital part of ordinary trees is 

 situated between the bark and the lignin. Every year a layer of lignin is deposited 

 on this part by the juices which are absorbed by the roots and worked up by the leaves ; 

 for this reason the age of trees may be determined by the number of lignin layers depo- 

 sited. The following year the juices travel over a new layer, and in this way the layer 

 already deposited serves only as a support for the vital parts of the tree. A living tree 

 may be regarded as an agglomeration of many plants living on one support. The woody 

 matter consists principally of fibrous tissue on to which the lignin or so-called incrust- 

 ing matter has been deposited. The tissue has the composition C6H 10 O 5 , the substance 

 deposited on it contains more carbon and hydrogen and less oxygen. This matter is 

 saturated with moisture when the wood is in a fresh state. Fresh birch wood contains 

 about 31 p.c. of water, lime wood 47 p.c., oak 35 p.c., pine and fir about 37 p.c. When 

 dried in the air the wood loses a considerable quantity of water and not more than 19 p.c. 

 remains. By artificial means this loss of water may be increased. If water be driven 

 into the pores of wood it becomes heavier than water, as the ligniu of which it is com- 

 posed has a density of about 1-6. One cubic centimetre of birch wood does not weigh 

 more than 0'901 grams, fir 0'894, lime tree 0'817, poplar 0'765 when in a fresh state ; when 

 in a dry state birch weighs 0'622, pine 0'550, fir 0'355, lime 0'430, guaiacum T342, 

 ebony 1*226. It is not out of place to remark here that on one deciatin (2*7 acres) 

 of woodland the yearly growth averages an amount of 3000 kilograms, or 180 poods of 

 \vood, but rarely reaches as much as 5000. The average chemical composition of wood dried 

 in air may be expressed as follows : Hygroscopic water 15 p.c., carbon 42 p.c., hydrogen 

 5 p.c., oxygen and nitrogen 37 p.c., ash 1 p.c. Wood parts with its hygroscopic water at 

 150, and decomposes at about 800, giving a brown, brittle, so-called red charcoal ; above 

 350 black charcoal is produced. From the above-mentioned average composition of 

 wood it is evident that the hydrogen may be accepted as being in about the quantity to 

 combine with the oxygen, as the hydrogen contained in the wood requires for its combus- 

 tion about forty parts by weight of oxygen. Therefore all that burns of the wood is the 

 carbon which it contains, 100 parts of wood only giving out as much heat as forty parts 

 of charcoal. Charcoal gives out much more useful heat than wood because the water con- 

 tained in the wood, or formed by the combination of its oxygen and hydrogen, has to be 



