100 



AGRICULTURAL CHEMISTRY. 



But if the hydrogen does not exist in 

 woody fibre in the form of water, the direct 

 oxidation of the carbon cannot be considered 

 as at all probable, without rejecting all the 

 facts established by experiment regarding 

 the process of combustion at low tempera- 

 tures. t 



If we examine the action of oxygen upon 

 a substance containing a large quantity of 

 hydrogen, such as alcohol, we find most 

 distinctly, that the direct formation of car- 

 bonic acid is the last stage of its oxidation, 

 and that it is preceded by a series of changes, 

 the last of which is a complete combustion 

 of the hydrogen Aldehyde, acetic, formic, 

 oxalic, and carbonic acids, form a connected 

 chain of products arising from the oxidation 

 of alcohol; and the successive changes 

 which this fluid experiences from the action 

 of oxygen may be readily traced in them. 

 Aldehyde is alcohol minw hydrogen; acetic 

 acid is formed by the direct union of alde- 

 hyde with oxygen. Formic acid and water 

 tire formed by the union of acetic acid with 

 oxygen. When all the hydrogen is removed 

 from this formic acid, oxalic acid is pro- 

 duced ; and the latter acid is converted into 

 carbonic acid by uniting with an additional 

 portion of oxygen. All these products 

 appear to be formed simultaneously, by the 

 action of oxidising agents on alcohol ; but 

 it can scarcely be doubted, that the forma- 

 tion of the last product, the carbonic acid, 

 does not take place until all the hydrogen 

 has been abstracted. 



The absorption of oxygen by drying oils 

 certainly does not depend upon the oxida- 

 tion of their carbon ; for in raw nut-oil, for 

 example, which was not free from mucilage 

 and other substances, only twenty-one vo- 

 lumes of carbonic acid were formed for 

 every 146 volumes of oxygen gas absorbed. 



It must be remembered, that combustion 

 or oxidation at low temperatures produces 

 results quite similar to combustion at high 

 temperatures with limited access of air. The 

 most combustible element of a compound, 

 which is exposed to the action of oxygen, 

 must become oxidised first, for its superior 

 i combustibility is caused by its being enabled 

 to unite with oxygen at a temperature at 

 which the other elements cannot enter into 

 that combination ; this property having the 

 same effect as a greater affinity. 



The combustibility of potassium is no 

 measure for its affinity for oxygen; we have 

 reason to believe that the attraction of mag- 

 nesium and aluminium for oxygen is greater 

 than that of potassium for the same element; 

 but neither of those metals oxidises either 

 in air or water at common temperatures 

 wnilst potassium decomposes water with 

 great violence, and appropriates its oxygen. 



Phosphorus and hydrogen combine with 

 oxygen at ordinary temperatures, the first 

 in moist air, the second when in contact 

 with finely-divided platinum ; while char- 

 coal requires a red heat before it can enter 

 into combination with oxygen. It is evi- 



dent that phosphorus and hyorogen are 

 more combustible than charcoal, that is, that 

 neir affinity for oxygen at common tempera- 

 ures is greater; and this is not the less cer- 

 ain, because it is found, that carbon in cer- 

 tain other conditions shows a much greater 

 affinity for oxygen than either of tnose sub- 

 stances. 



In putrefaction, the conditions are evi 

 dently present, under which the affinity of 

 carbon for oxygen comes into play; neither 

 expansion, cohesion, nor the gaseous state, 

 opposes it, whilst in eremacausis all these 

 restraints have to be overcome. 



The evolution of carbonic acid, during 

 the decay or eremacausis of animal or vege- 

 table bodies which are rich in hydrogen, 

 must accordingly be ascribed to a transposi- 

 tion of the elements or disturbance in their 

 attractions, similar to that which gives rise 

 to the formation of carbonic acid in the pro- 

 cesses of fermentation 'and putrefaction. 



The eremacausis of such substances is, 

 therefore, a decomposition analogous to the 

 putrefaction of azotised bodies. For in these 

 there are two affinities at play ; the affinity 

 of nitrogen for hydrogen, and that of carbon 

 for oxygen, and both facilitate the disunion 

 of the elements. Now there are two affini- 

 ties also in action in those bodies whicn de- 

 cay with the evolution of carbonic acid. 

 One of these affinities is the attraction of the 

 oxygen of the air for the hydrogen of the 

 substance, which corresponds to Ihe attrac- 

 tion of nitrogen for the same element ; and 

 the other is the affinity of the carbon of the 

 substance for its oxygen, which is constant 

 under all circumstances. 



When wood putrefies in marshes, carbon 

 and oxygen are separated from its elements 

 in the form of carbonic acid, and hydrogen 

 in the form of carburetted hydrogen. But 

 when wood decays or putrefies in the air, 

 its hydrogen does not combine with carbon, 

 but with oxygen, for which it has a much 

 greater affinity at common temperatures. 



Now it is evident from the complete simi- 

 larity of these processes, that decaying and 

 putrefying bodies can mutually replace one 

 another in their reciprocal actions. 



All putrefying bodies pass into the state 

 of decay, when exposed freely to the air, 

 and all decaying matters into that of putre- 

 faction when air is excluded. All bodies, 

 likewise, in a state of decay are capable of 

 inducing putrefaction in other bodies in the 

 same manner as putrefying bodies them 

 selves do. 



CHAPTER VII. 



EREMACAITSIS OR DECAY OP BODIES DESTI- 

 TUTE OF NITROGEN: FORMATION OF ACETIC 

 ACID. 



ALL those substances which appear to 

 possess the property of entering spontar.e- 



