DECAY OF WOODY FIBRE. 



Ill 



the remarkable result is obtained, that the j 

 proportion of carbon in the different products j 

 augments. Consequently, if we did not ] 

 take into consideration the evolution of car- 

 bonic acid under the influence of the air, 

 the conversion of wood into humus might ' 

 be viewed as a removal of the elements of 

 water from the carbon. 



The analysis of mouldered oak wood, 

 which was taken from the interior of the I 

 trunk of an oak, and possessed a chocolate ! 

 brown colour and the structure of wood, I 

 showed that 100 parts of it contained 53" 36 

 parts of carbon and 46*44 parts of hydrogen 

 and oxygen in the same relative proportions 

 as in water. From an examination of 

 mouldered wood of a light brown colour, 

 easily reducible to a fine powder, and taken 

 from another oak, it appeared that it con- 

 tained 56-21 1 carbon and 43789 water. 



These indisputable facts point out the 

 similarity of the decay of wood with the 

 slow combustion or oxidation of bodies 

 which contain a large quantity of hydrogen. 

 Viewed as a kind of combustion, it would 

 indeed be a very extraordinary process, if 

 the carbon combined directly with the oxy- 

 gen ; for it would be a combustion in which 

 the carbon of the burning body augmented 

 constantly, instead of diminishing. Hence 

 it is evident that it is the hydrogen which is 

 oxidised at the expense of the oxygen of the 

 air ; wnile the carbonic acid is formed from 

 the elements of the wood. Carbon never 

 combines at common temperatures with 

 oxygen, so as to form carbonic acid. 



In whatever stage of decay wood may be, 

 its elements must always be capable of be- 

 ing represented by their equivalent numbers. 



The following formula illustrates this fact 

 with great clearness : 



C36 H22 O22 oak wood, according to Gay- 

 Lussac and Thenard.* 



C35 H20 O20 humus from oak wood (Meyer.)t 

 C34 HIS 18 humus from oak wood (Dr. 



Will.)* 



It is evident from these numbers that for 

 every two equivalents of hydrogen which 

 are oxidised, two atoms of oxygen and cne 

 of carbon are set free. 



Under ordinary circumstances, woody 

 fibre requires a very long time for its decay ; 

 but this process is of course much accele- 

 rated by an elevated temperature and free un- 

 restrained access of air. The decay, on the 

 contrary, is much retarded by absence of 

 moisture, and by the wood being surrounded 

 with an atmosphere of carbonic acid, which 

 prevents the access of air to the decaying 

 matters. 



Sulphurous acid, and all antiseptic sub- 

 stances, arrest the decay of woody fibre. It 



* The calculation gives 52'5 carbon, and 47'5 

 water. 



t The calculation gives 54 carbon, and 46 

 water. 



t Tlv. Calculation gives 56 carbon, and 44 

 water. 



is well known that corrosive sublimate is 

 employed for the purpose of protecting the 

 timber of ships from decay; it is a substance 

 which completely deprives vegetable or ani- 

 mal matters, the most prone to decomposi- 

 tion, of their property of entering into fer- 

 mentation, putrefaction, or decay. 



But the decay of woody fibre is very 

 much accelerated by contact with alkalies or 

 alkaline earths; for these enable substances 

 to absorb oxygen, which do not possess 

 this power themselves; alcohol, gallic acid, 

 tannin, the vegetable colouring matters, and 

 several other substances, are thus affected 

 by them. Acids produce quite an opposite 

 effect; they greatly retard decay. 



Heavy soils, consisting of loam, retain 

 longest the most important condition for the 

 decay of the vegetable matter contained in 

 them, viz., water; but their impermeable 

 nature prevents contact with the air. 



In moist sandy soils, particularly such as 

 are composed of a mixture of sand and car- 

 bonate of lime, decay proceeds very quickly, 

 it being aided by the presence of the slightly 

 alkaline lime. 



Now let us consider the decay of woody 

 fibre during a very long period of lime, and 

 suppose that its cause is the gradual removal 

 of the hydrogen in the form of water, and 

 the separation of its oxygen in that of car- 

 bonic acid. It is evident that if we sub-" 

 tract from the formula C 36 , H 22 , O 22 , the 22 

 equivalents of oxygen, with 11 equivalents 

 of carbon, and 22 equivalents of hydrogen, 

 which are supposed to be oxidised by *he 

 oxygen of the air, and separated in the form 

 of water; then from 1 atom of oak wood, 

 25 atoms of pure carbon will remain as the 

 final product of the decay. In other words, 

 100 parts of oak, which contain 52'5 parts 

 of carbon, will leave as a residue 37 parts 

 of carbon, which must remain unchanged, 

 since carbon does not combine with oxygen 

 at common temperatures. 



But this final result is never attained in 

 the decay of wood under common circum- 

 stances ; and for this reason, that with the 

 increase of the proportion of carbon in the 

 residual humus, as in all decompositions of 

 this kind, its attraction for the hydrogen, 

 which still remains in combination, also in- 

 creases, until at length the affinity of oxygen 

 for the hydrogen is equalled by that of the 

 carbon for the same element. 



In proportion as the decay of woody fibre 

 advances, its property of burning with flame, 

 or in other words, of developing carburetted 

 hvdrogen on the application of heat, dimi- 

 nishes. Decayed wood burns without flame; 

 whence no other conclusion can be drawn, 

 than that the hydrogen, which analysis 

 shows to be present, is not contained in it 

 in the same form as in wood. 



Decayed oak contains more carbon than 

 fresh wood, but its hydrogen and oxygen 

 are in the same proportion. 



We would naturally expect that the flame 

 given out by decayed wood should be more 



