382 POISONS, CONTAGIONS, MIASMS. 



effected by pure gluten, and by dilute mineral 

 acids. 



From all the preceding facts, we see that very 

 various transpositions, and changes of composition 

 and properties, may be produced in complex organic 

 molecules, by every cause which occasions a dis- 

 turbance in the attraction of their elements. 



When moist copper is exposed to air containing 

 carbonic acid, the contact of this acid increases the 

 affinity of the metal for the oxygen of the air in so 

 great a degree that they combine, and the surface 

 of the copper becomes covered with green car- 

 bonate of copper. Two bodies, which possess the 

 power of combining together, assume, however, 

 opposite electric conditions at the moment at which 

 they come in contact. 



When copper is placed in contact with iron, a 

 peculiar electric condition is excited, in consequence 

 of which the property of the copper to unite with oxy- 

 gen is destroyed, and the metal remains quite bright. 



When formate of ammonia is exposed to a tem- 

 perature of 388 F. (180 C.) the intensity and 

 direction of the chemical force undergo a change, 

 and the conditions under which the elements of 

 this compound are enabled to remain in the same 

 form cease to be present. The elements, therefore, 

 arrange themselves in a new form ; hydrocyanic 

 acid and water being the results of the change. 



Mechanical motion, friction, or agitation, is suffi- 

 cient to cause a new disposition of the constituents 



