104 COMPOSITION OF WOOD. 



did we not know that woody fibre, when heated or distilled, cannot be 

 resolved into carbon (charcoal) and water alone^ and, therefore, cannot 

 be supposed to consist of these alone. 



It is a remarkable character of this substance, however, that these two 

 elements, hydrogen and oxygen, exist in it in the proportions to form 

 water, and we shall find the knowledge of this fact of great importance 

 to us, when we come to inquire how this constituent of vegetables is 

 formed — from the food on which they live. 



2°. If a portion of the wood of a tree be dried and analyzed without 



being previously digested in water, alcohol, and ether, as long as any 



thing is taken up, the proportion of the constituents is found to vary 



slightly with the species of tree, but in all cases the hydrogen is in larger 



quantity than is necessary to form water with the oxygen they contain. 



Thus, according to Payen, the dry wood of the following trees consists of 



Ebony. Walnut. Oak. Beech. 



Carbon . . . 52-85 51-92 60-00 49-25 



Hydrogen . . 6-00 5 96 6-20 6-10 



Oxygen . . . 41-15 42-12 43'80 44-65 



100 100 100 100 



The carbon in these several kinds of wood differs as much as three 

 per cent., but in each of them the product of the hydrogen, when multi 

 plied by 8, is considerably greater than the per centage of oxygen. 



3°. When the solid substance of wood is examined under the micro- 

 scope it is observed to consist of two portions or kinds of matter, that of 

 which ihe original sides of the cells and tubes is composed, called the 

 cellular matter — the true woody fibre — and of a solid substance by which 

 the cells are internally coated and strengthened, called the incrusting 

 matter. It is in this latter substance that the excess of hydrogen, exhi- 

 bited by the preceding analysis, is suf)posed to exist, the true woody 

 fibre containing always the hydrogen arid oxygen in the proportions ne- 

 cessary to form water.* 



• Payen at first considered this incrusting matter as a peculiar substance, for which he 

 proposed the name of sclerogene. His first mode of separating it from the cellular matter 

 was by treating the finely rasped wood (of the oak and beech) with nitric acid, which dis- 

 solved out the incrusting matter and left the cellular matter behind. His second mode was 

 to digest the wood with dilute sulphuric acid, by which the cellular matter was dissolved 

 out, and the incrusting matter left. It is obvious, however, that no reliance whatever can be 

 placed on the analyses of substances so treated, since they cannot fail to have undergone a 

 chemical change by being exposed to the action of these strong acids. Further examination 

 has satisfied Payen that the incrusting matter consists of at least three substances, of which 

 one is soluble in water, alcohol, and ether, another in alcohol only, while the third is insolu- 

 ble in any of these liquids. They are composed, according to his analyses, of 



Soluble in Soluble in 



Insoluble. alcohol only. water and alcohol. 



Carbon ... 48 628 6853 



Hydrogen ... 6 59 704 



Oxygen ... 46 31-3 2443»- 



100 100 100 



It is impossible to say how far the substances analysed by Payen are to be considered as 

 pure, or as actually existing in the pores, or in the incrusting matter of the woody fibre, but 

 it is obvious that the presence of a variable quantity of such substances will necessarily 

 cause that excess of hydrogen, in the entire wood, which appears in the analysis of the ebo- 

 ny, walnut, oak, and beech woods, given in the text. That such an excess of hydrogen 

 above what is necessary to form water with the oxygen, does exist in the wood of most trees 



[^ Meyen's Jahresbericht, 1839, p. 10.] 



