Ion Exchange 



The replacement of one kind of ion by another, e.g., 

 hydrogen ions replacing calcium ions in certain soil solutions. 

 See Exchange capacity. 



lonization 



The process of ion formation. 



Ionizing Radiation 



Radiation that takes electrons from atoms and attaches 

 them to other atoms, e.g., Alpha, Beta, Gamma radiation, 

 (q. v.). 



Irradiance 



The receipt of radiant energy per unit area per unit of 

 time. On a clear summer day solar radiant energy equals 

 1.2 to 1.5 gram-calories per square centimeter per minute 

 at noon. cf. Illuminance, Light intensity. 



Irradiation 



The exposure of an object to radiation such as sunlight, 

 Ionizing radiation, etc. 



Irritability 



The characteristic capability of an organism to respond 

 to a stimulus, e.g., a plant growing towards the light. 



Irruption 



An abrupt, irregular increase in population number or 

 size. 



Isobar 



A line drawn on a map or chart connecting places of 

 equal barometric pressure. 



Isobath 



A line drawn on a map connecting points of equal depth 

 on the bottom of the sea. 



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