CHEMICAL TRANSFORMATIONS. 



combination with any of its constituents. 

 In this respect, its decomposition depends 

 evidently upon the same causes which effect 

 that of iodide of nitrogen, or fulminating 

 silver. Yet it is singular that the cause of 

 the sudden separation of the component 

 parts of peroxide of hydrogen has been 

 viewed as different from those of common de- 

 composition, and has been ascribed to a new 

 power termed the catalytic force. Now, it 

 has not been considered, that the presence 

 of the platinum and silver serves here only 

 to accelerate the decomposition ; for without 

 the contact of these metals, the peroxide of 

 hydrogen decomposes spontaneously, al- 

 though very slowly. The sudden separa- 

 tion of the constituents of peroxide of hydro- 

 gen differs from the decomposition of gase- 

 ous hypochlorous acid, or solid iodide of 

 nitrogen, only in so far as the decomposition 

 takes place in a liquid. 



A remarkable action of peroxide of hydro- 

 gen has attracted much attention, because it 

 differs from ordinary chemical phenomena. 

 This is the reduction which certain oxides 

 suffer by contact with this substance, on the 

 instant at which the oxygen separates from 

 the water. The oxides thus easily reduced, 

 are those of which the whole, or part at 

 least, of their oxygen is retained merely by 

 a feeble affinity, such as the oxides of silver 

 and of gold, and peroxide of lead. 



Now, other oxides which are very stable 

 in composition, effect the decomposition of 

 peroxide of hydrogen, without experiencing 

 the smallest change; but when oxide of 

 silver is employed to effect the decomposi- 

 tion, all the oxygen of silver is carried away 

 with that evolved from the peroxide of hy- 

 drogen, and as a result of the decomposition, 

 water and metallic silver remain. When 

 peroxide of lead is used for the same pur- 

 pose, half its oxygen escapes as a gas. Per- 

 oxide of manganese may in the same man- 

 ner be reduced to the protoxide, and oxygen 

 set at liberty, if an acid is at the same time 

 present, which will exercise an affinity for 

 the protoxide and convert it into a soluble 

 salt. If, for example, we add to peroxide 

 of hydrogen sulphuric acid, and then per- 

 oxide of manganese in the state of fine pow- 

 der, much more oxygen is evolved than the 

 compound of oxygen and hydrogen could 

 yield ; and if we examine the solution which 

 remains, we find a salt of the protoxide of 

 manganese, so that half of the oxygen has 

 been evolved from the peroxide of that metal. 



A similar phenomenon occurs, when car- 

 bonate of silver is treated with several or- 

 ganic acids. Pyruvic acid, for example, 

 combines readily with pure oxide of silver, 

 and forms a salt of sparing solubility in 

 water. But when this acid is brought in 

 contact with carbonate of silver, the oxygen 

 of part of the oxide escapes with the car- 

 bonic acid, and metallic silver remains in 

 the state of a black powder. (Berzelius.) 



Now no other explanation of these phe- 

 nomena cun be given, than that a'bedy in 

 12 



the act of combination or decomposition 

 enables another body, with which it is in 

 contact, to enter into the same state. It is 

 evident that the active state of the atoms of 

 one body has an influence upon the atoms 

 of a body in contact with it; and if these 

 atoms are capable of the same change as the 

 former, they likewise undergo that change;, 

 and combinations and decompositions are the. j 

 consequence. But when the atoms of the^~ 

 second body are not capable of such an 

 action, any further disposition to change 

 ceases from the moment at which the atoms 

 of the first body assume the state of rest,, 

 that is when the changes or transformations 

 of this body are quite completed. 



This influence exerted by one compound 

 upon the other, is exactly similar to that 

 which a body in the act of combustion exer- 

 cises upon a combustible body in its vicinity ; 

 with this difference only, that' the causes 

 which determine the participation and du- 

 ration of these conditions are different. For ""> 

 the cause, in the case of the combustible 

 body, is heat, which is generated every mo- 

 ment anew ; whilst in the phenomena of 

 decomposition and combination, which we 

 ! are considering at present, the cause is a 

 body in the state of chemical action, which 

 exerts the decomposing influence only so 

 long as this action continues. 



Numerous facts show that motion alone 

 exercises a considerable influence on chemi- 

 cal forces. Thus, the power of cohesion 

 does not act in many saline solutions, even 

 when they are fully saturated with salts, if 

 they are permitted to cool while at rest. In 

 I such a case, the salt dissolved in a liquid 

 does not crystallize; but when a grain of 

 ' sand is thrown into the solution, or when it 

 ( receives the slightest movement, the whole 

 liquid becomes suddenly solid while heat 

 is evolved. The same phenomenon happens 

 with water, for this liquid may be cooled 

 much under 32 F. (0 C.,) if kept com- 

 pletely undisturbed, but solidifies in a mo- 

 ment when put in motion. 



The atoms of a body must in fact be set 

 in motion before they can overcome the vis 

 inertice so as to arrange themselves into cer- 

 tain forms. A dilute solution of a salt of 

 potash mixed with tartaric acid yields no 

 precipitate whilst at rest ; out if motion is 

 communicated to the solution by agitating 

 it briskly, solid crystals of cream of tartar 

 are deposited. A solution of a salt of mag- 

 nesia also, which is not rendered turbid by 

 the addition of phosphate of ammonia, de- 

 posits the phosphate of magnesia and am- 

 monia on those parts of the vessel touched 

 with the rod employed in stirring. 



In the processes of combination and de 

 composition under consideration, motion, by 

 overcoming the vis inertice, gives rise im- 

 mediately to another arrangement of the 

 atoms of a body, that is, to the production 

 of a compound which did not before exist in 

 it. Of course these atoms must previously 

 possess the power of arranging themselves 



H2 



