526 



ILL USTRA TI VE EXPERIMENTS 



III. jM . 5-8-8-0 (Physiological Range). 

 Solutions : 50 c.c. solution (ii.), and cT c.c. of N/5NaOH. 



Indicators, 



Brom-cresol purple ; brom-thyniol blue ; 

 or Phenol red. 

 Dilute to 200 c.c. 



IV. Range 7-8-10-0 



Place 50 c.c of solution (iii.) in a number of 200 c.c. flasks. Add to each 

 a drop of one of the indicators cresol red or thymol blue and the number of 

 cubic centimetres of solution (iv.) given below. 



To demonstrate the acid-combining power of a "buffered" solution. 



Take 50 c.c. of the above nu.xture { pH = 7'8) or prepare a .Mjlution con- 

 taining about 0-25 per cent, sodium bicarbonate. Place this in a tall 

 cylinder and in another similar vessel place the same quantity of water. 



