32 GENERAL PROPERTIES OF LIVING TISSUES 



increase upon this further addition of water. 

 Observation shows that it does increase. It 

 must therefore depend on the degree of dissocia- 

 tion, i. e. the number of ions. 



When the solution is heated, its viscosity and 

 thus its fluid friction diminishes ; the ions pass 

 through it with less difficulty and the conduc- 

 tivity rises. Non-conducting substances added 

 to aqueous solutions may affect both the number 

 and the speed of the ions. The first additions 

 of alcohol to a dilute solution increase the vis- 

 cidity, and lessen the speed of the ions ; after a 

 certain limit, further additions have little effect 

 on the speed, but markedly lessen the number 

 of the ions, i. e. the degree of ionisation or dis- 

 sociation. Comparisons of electrical conductivity 

 in solutions of different concentration can be 

 made only when the rate at which the ions 

 move remains the same ; in other words, the 

 salt, the solvent, and the temperature must be 

 the same in the two solutions. 



Electrolytic solution Pressure. When a salt 

 is placed in water it dissolves until its solution 

 pressure or tendency to pass into solution is 

 balanced by the osmotic pressure of the dissolved 

 particles. If the osmotic pressure exceed the 

 solution pressure, salt will be deposited. As 

 the salt dissolves, positive and negative ions are 



