RASKINS' MODIFICATION 



29 



solutions can still be used satisfactorily when two months old, 

 although the rosolic acid weakens slightly in that time. New 

 solutions should be prepared once in two or three months. 



PERMANENT STANDARDS AND THE CORRESPONDING 

 SORENSEN STANDARDS 



Technic in Estimating P H of Urine 



All glassware used (bottles, pipettes, flasks, etc.) must be 

 thoroughly washed, rinsed with distilled water, and then tested 

 with a practically neutral indicator solution (e.g., 20 c.c. distilled 

 water, 1 drop of the buffer phosphate solution and 1 c.c. of rosolic 

 acid). If the test solution becomes less red, contaminating acid 

 is. present, if it becomes redder, alkali is present; in either case 



