286 WHAT IS LIFE 



Chemical Analysis. See Analysis, Chemical. 



Chemical Changes and Radioactivity, The Difference 

 Between. In chemical changes molecules are formed 

 or decomposed; in radioactivity atoms are disinte- 

 grated. In chemical changes the nuclei of the atoms 

 that are involved remain unaltered in constitution; 

 in radioactivity the nucleus of the atom suffers the 

 loss of one or more constituents. In chemical changes 

 the atoms (elements) remain unchanged; in radio- 

 activity the element is changed, transmuted, into 

 another element. The energy liberated in radio- 

 activity is millions of times greater than any energy 

 liberated in chemVal changes. 



Chemotaxis, Positive. The property possessed by 

 certain living cells (that are capable of spontaneous 

 motion) of moving towards certain substances. 



Chromatin. The minute granules that constitute 

 the chromoplasm (the readily stained parts) of a 

 cell-nucleus. 



Coagulation. The precipitation of a colloid. In 

 some colloids the disperse phase is separated from 

 the dispersion medium by heat, in others by the 

 addition of a small quantity of an electrolyte, etc. 

 See Disperse Phase and Dispersion Medium. 



Compton Effect. In a very interesting and dif- 

 ficult experiment, involving the scattering of X-rays 

 (of molybdenum) by free electrons, the shifting of a 

 characteristic spectral line from blue to red, indicat- 

 ing the change of the "waves" from a shorter to a 

 longer wave-length, or a higher to a lower frequency. 

 This effect is produced as the result of the collision 

 of "light-quanta" with free electrons, in which 

 collision the light-quant transfers some of its energy 

 to the electron, and thus with a smaller energy is 

 changed to a lower frequency, which latter registers 

 as a shifting of lines. The experiment was designed 



