20 CHEMISTRY AND PHYSICS IN RELATION 



ration of the nitric acid. The solution of the platinum and copper follows in both 

 cases against the electrical laws ; heat or other causes, which might increase the 

 affinity, have no share in the process. 



INFLUENCE OF THE SAME CONDITION UPON THE CAPACITY OF 

 BODIES TO SUFFER DECOMPOSITION. 



If, further, binoxide of hydrogen be brought into contact with hyper-oxide of 

 lead or hyper-oxide of silver, the decomposition of the former is accelerated, as 

 by many solid bodies, and it is resolved, with effervescence, into oxygen and 

 water ; but the molecules of both metallic oxides undergo a like decomposition 

 when in contact with the decomposing parts of the binoxide of hydrogen ; oxide 

 silver is resolved into oxygen and the metal, hyper-oxide of lead into oxygen and 

 oxide of lead. Both oxides behave as if they had been exposed to a faint red 

 heat. 



It follows, from these appearances, that the condition of the combination or 

 decomposition of a body, or of its change of place or motion, may exercise an 

 influence upon the molecules of many other combinations brought in contact with 

 it ; they pass into the same condition ; their elements are in a like manner sepa- 

 rated, and they thus gain the power, which they did not possess in themselves, of 

 entering into a combination. 



The decomposition of the second body naturally proves that the resistance of the 

 force, which strives to hold the atoms together in their original mode of arrange- 

 ment, must be less than the force of that activity which affects it. 



INFLUENCE OF A SIMILAR CONDITION UPON ORGANIC SUBSTANCES. 



The property possessed by any substance in combination or decomposition, to 

 call forth in other bodies of similar or dissimilar nature in contact with it, a condi- 

 tion of form and character like its own, belongs, in a much higher degree, to 

 organic bodies than to inorganic substances. 



DECAYED WOOD. 



Decayed wood brought in contact with that which is sound, changes gradually 

 the sound body, under similar conditions, to a state of decomposition. 



RELATION OF UREA AND HIPPURIC ACID IN URINE. 



In fresh urine, if there is a complete exclusion of oxygen, no change of the 

 urea, or of the hippuric acid contained in it occur ; or exposure to the air, another 

 substance, occurring in urine in consequence of the oxygen being taken up, suffers 

 a change in form and properties, which is communicated to the urea and the 

 hippuric acid. Urea is decomposed into carbonic acid and ammonia, and in the 

 place of the hippuric acid which disappears, benzoic acid is found. 



INFLUENCE OF THE PUTREFACTION OF WOOD ON THE OXIDATION 



OF HYDROGEN. 



Decayed wood takes up oxygen from the air, and gives out an equal volume of 

 carbonic acid. If hydrogen be added to the air, it becomes oxidized with the 



