340 



PRACTICAL PHYSIOLOGY 



PHOSPHATE MIXTUBES. 



To test the " buffer " action of salts like sodium bicarbonate, compare 

 the amounts of decinormal hydrochloric acid which must be added to 

 obtain the turning point of an indicator such as methyl orange, (a) 

 using 10 c.c. distilled water and (b) 10 c.c. of a 0-25 per cent, solution of 

 sodium bicarbonate. Repeat this experiment with solutions of phos- 

 phates, citrates and acetates. 



A similar type of experiment may be done, using bromthymol blue 

 or phenol red as indicator, by breathing through (one full expiration) 

 (a) 0-25 per cent, sodium chloride, (b) 0-25 N, (c) 0-025 N, and (d) 0-0025 N 

 sodium bicarbonate solutions. 



Standard tubes of the various solutions containing identical amounts 

 of the indicators (5 drops) should be prepared for comparison. Try 

 experiment with each indicator. 



Similar tests may be made of the reaction of the blood, but the dialysis 

 method introduced by Dale and Evans (Jour, of PhysioL, 1920, 54, 

 167) gives much more accurate results. 



