88 



AGRICULTURAL CHEMISTRY. 



one of which ammonia possesses the j an alloy of copper, zinc, and nickel, dis- 

 power of uniting with the acting body. j solves easily in this acid with evolution of 



Inorganic chemistry can present instances hydrogen gas. 



analogous to this class of decomposition ! Tin decomposes nitric acid with great fa- 

 also; but there are forms of organic chemi- cility, but water with difficulty; and yet, 

 cal decomposition of a very different kind, when tin is dissolved in nitric acid, hydrogen 

 in which none of the component parts of the | is evolved at the same time, from a'decom- 

 matter which suffers decomposition enter j position of the water contained in the acid 

 into combination with the body which de- ! 

 termines the decomposition. In cases of 



this kind a disturbance is produced in the 

 mutual attraction of the elements of a com- 

 pound, and they in consequence arrange 

 themselves into one or several new combi- 

 nations, which are incapable of suffering 

 farther change under the same conditions. 



When, by means of the chemical affinity 

 of a second body, by the influence of heat, 

 or through any other causes, the composi- 

 tion of an organic compound is made to 

 undergo such a change, that its elements 

 form two or more new compounds, tnis 

 manner of decomposition is called a chemi- 

 cal transformation or metamorphosis. It is 

 an essential character of chemical transfor- 

 mations, that none of the elements of the 

 body decomposed are singly set at liberty. 



The changes, which are designated by the 

 terms fermentation, decay, and putrefaction, 

 are chemical transformations effected by an 

 agency which has hitherto escaped atten- 

 tion, but the existence of which will be 

 proved in the following pages. 



CHAPTER II 



ON THE CAUSES WHICH EFFECT FERMENTA- 

 TION, DECAY,* AND PUTREFACTION. 



ATTENTION has been recently directed to 

 the fact, that a body in the act of combina- 

 tion or decomposition exercises an influence 

 upon any other body with which it may be 

 in contact. Platinum, for example, does 

 not decompose nitric acid ; it may be boiled 

 with this acid without being oxidized by it, 

 even when in a state of such fine division, 

 that it no longer reflects light (black spongy 

 platinum.) But an alloy of silver and pla- 

 tinum dissolves with great ease in nitric 

 acid ; the oxidation which the silver suffers 

 causes the platinum to submit to the same 

 change; or, in other words, the latter body, 

 from its contact with the oxidizing silver, 

 acquires the property of decomposing nitric 

 acid. 



and ammonia is formed in addition to oxide 

 of tin. 



In the examples here given the only com- 

 bination or decomposition which can be ex- 

 plained by chemical affinity is the last. In 

 the other cases, electrical action ought to 

 have retarded or prevented the oxidation of 

 the platinum or copper while they were in 

 contact with silver or zinc, but, as experience 

 shows, the influence of the opposite electri- 

 cal conditions is more than counterbalanced 

 by chemical actions. 



The same phenomena are seen in a less 

 dubious form in compounds, the elements 

 of which are held together only by a feeble 

 affinity. It is well known that there are 

 chemical compounds of so unstable a nature, 

 that changes in temperature and electrical 

 condition, or even simple mechanical fric- 

 tion, or contact with bodies of apparently 

 totally indifferent natures, cause such a dis- 

 turbance in the attraction of their constituents, 

 that the latter enter into new forms, with- 

 out any of them combining with the acting 

 body. These compounds appear to stand 

 but just within the limits of chemical combi- 

 nation, and agents exercise a powerful influ- 

 ence over them, which are completely de- 

 void of action on compounds of a stronger 

 affinity. Thus, by a slight increase of tem- 

 perature, the elements of hypochlorous acid 

 separate from one another with evolution of 

 heat and light; chloride of nitrogen explodes 

 by contact with many bodies, which com- 

 bine neither with chlorine nor nitrogen at 

 common temperatures ; and the contact of 

 any solid substance is sufficient to cause the 

 explosion of iodide of nitrogen, or fulminat- 

 ing silver. 



It has never been supposed that the causes 

 of the decomposition of these bodies should 

 be ascribed to a peculiar power, different 

 from that which regulates chemical affinity, 

 a power which mere contact with the down 

 of a feather is sufficient to set in activity, 

 and which, once in action, gives rise to 

 the decomposition. These substances have 

 always been viewed as chemical compounds 

 of a very unstable nature, in which the 

 component parts are in a state of such ten- 



Copper does not decompose water, even s j on) that the least disturbance overcomes 

 when boiled in dilute sulphuric acid ; but | their chemical affinity. They exist only by 



the vis inertise, and any shock or movement 

 is sufficient to destroy the attraction of their 

 component parts, and consequently their 

 existence in their definite form. 



Peroxide of hydrogen belongs to this class 

 of bodies ; it is decomposed by all substances 

 capable of attracting oxygen from it, and 



* An essential distinction is drawn in the follow- 

 ing part of the work, between decay and putre- 

 faction (Verwesung und Faulniss,) and they are 

 shown to depend on different causes ; but as the 

 word decay is not generally applied to a distinct 

 species of decomposition, and does not indicate its 

 true nature, 1 shall in future, at the suggestion of . 



he author! employ the term eremacansis, the even by contact with many bodies, such as 

 meaning of which has been already explained. ED. ! platinum or silver, which do not enter into 



