AGRICULTURAL CHEMISTRY. 



influence upon it, we find, that these changes ! combined, to undergo the same decomposi- 



are not confined to any narrow limits, like 



those of inorganic bodies, but are in fact 



unlimited. 

 The elements of sugar yield to every at- 



<.raction, and to each in a peculiar manner. 



In inorganic compounds, an acid acts upon 



a particular constituent of the body, which 



it decomposes, by virtue of its affinity for 



that constituent, and never resigns its proper 



chemical character, in whatever form it may 



be applied. But when it acts upon sugar, 

 I and induces great changes in that compound, 

 1 it does this not by any superior affinity for 

 | a base existing in the sugar, but by disturb- 

 Ung the equilibrium in the mutual attraction 

 iof the elements of the sugar amongst them- 

 jselves. Muriatic and sulphuric acids, which 



differ so much from one another both in 



characters and composition, act in the same 



manner upon sugar. But the action of both 



varies according to the state in which they 



are ; thus they act in one way when dilute, 



in another when concentrated, and even dif- 

 ferences in their 

 their action 



in 



ir temperature cause a change 

 . Thus sulphuric acid of a 

 moderate degree of concentration converts 

 sugar into a black carbonaceous matter, 

 forming at the same time acetic and formic 

 acids. But when the acid is more diluted, 

 the sugar is converted into two brown sub- 

 stances, both of them containing carbon and 

 the elements of water. Again, when sugar 

 is subjected to the action of alkalies, a whole 

 series of different new products are obtained ; 

 wnile oxidizing agents, such as nitric acid, 

 produce from it carbonic acid, acetic acid, 

 oxalic acid, formic acid, and many other 

 products which have not yet been examined. 



If from the facts here stated we estimate 

 the power with which the elements of sugar 

 are united together, and judge of the force 

 of their attraction by the resistance which 

 they offer to the action of bodies brought 

 into contact with them, we must regard the 

 atom of sugar as belonging to that class of 

 compound atoms, which exist only by the 

 vis inerticK of their elements. Its elements 

 seem merely to retain passively the position 

 and condition in which they had been 

 placed, for we do not observe that they re- 

 sist a change of this condition by their own 

 mutual attraction, as is the case with sul- 

 phate of potash. 



Now it is only such combinations as 

 sugar, combinations therefore which possess 

 a very complex molecule, which are capa- 

 ble of undergoing the decompositions named 

 fermentation and putrefaction. 



We have seen that metals acquire a power 

 vhich they do not of themselves possess, 

 nauiely, that of decomposing water and 

 nitric acid, by simple contact with other 

 metals in the act of chemical combination. 

 We have also seen, that peroxide of hydro- 

 gen and the persulphuret of the same ele- 

 ment, in the act of decomposition, cause 

 other compounds of a similar kind, but of 

 which the elements are much more strongly 



tion, although they exert no chemical af- 

 finity or attraction for them or their consti- 

 tuents. The cause which produces these 

 phenomena will be also recognised, by at- 

 tentive observation, in those matters which 

 excite fermentation or putrefaction. All 

 bodies in the act of combination or decom- 

 position have the property of inducing those 

 processes ; or, in other words, of causing a 

 disturbance of the statical equilibrium in 

 the attractions of the elements of complex 

 organic molecules, in consequence of which 

 those elements group themselves anew, ac- 

 cording to their special affinities. 



The proofs of the existence of this cause 

 of action can be easily produced ; they are 

 found in the characters of the bodies which 

 effect fermentation and putrefaction, and in 

 the regularity with which the distribution 

 of the elements takes place in the subse- 

 quent transformations. This regularity de- 

 pends exclusively on the unequal affinity 

 which they possess for each other in an 

 isolated condition. The action of water on 

 wood, charcoal, and cyanogen, the simplest 

 of the compounds of nitrogen, suffices to il- 

 lustrate the whole of the transformations of 

 organic bodies; of those in which nitrogen 

 is a constituent, and of those in which it is 

 absent. 



CHAPTER IV. 



ON THE TRANSFORMATION OF BODIES WHICH 

 DO NOT CONTAIN NITROGEN AS A CONSTI- 

 TUENT, AND OF THOSE IN WHICH IT IS 

 PRESENT. 



WHEN oxygen and hydrogen combined 

 in equal equivalents, as in steam, are con- 

 ducted over charcoal, heated to the tempe- 

 rature at which it possesses the power to 

 enter into combination with one of these 

 elements, a decomposition of steam ensues. 

 An oxide of carbon (either carbonic oxide 

 or carbonic acid) is under all circumstances 

 formed, while the hydrogen of the water is 

 liberated, or, if the temperature be sufficient, 

 unites with the carbon, forming carburetted 

 hydrogen. Accordingly, the carbon is shared 

 between the elements of the water, the oxy- 

 gen and hydrogen. Now a participation of 

 this kind, but even more complete, is ob- 

 served in every transformation, whatever 

 be the nature of the causes by which it is 

 effected. 



Acetic and meconic* acids suffer a tine 

 transformation under the influence of heat, 

 that is, their component elements are dis- 

 united, and form new compounds without 

 any of them being singly disengaged. Acetic 

 acid is converted into acetone and carbonic 



* An acid existing in opium, and named from 

 the Greek for poppy. 



