144 



PRACTICAL PHYSIOLOGY. 



[xxiit. 



natant fluid has a straw-yellow colour, not a trace of blue remain- 

 ing. This is best seen when the capsule is tilted. It is not 

 advisable to spend too much time in determining when the blue 

 colour disappears, as it is apt to return on cooling. It is sometimes 

 difficult to determine when all the blue colour has disappeared. 

 The following process is useful. Filter a little 

 of the hot fluid, acidulate with acetic acid and 

 add potassic ferrocj^anide. If copper is present 

 a brown colour or precipitation is produced. If 

 this be so, add more urine until no brown colour 

 is produced. 



[Pavy's modification of Fehling's solution is sometimes 

 used. In it ammonia holds the cojjper in solution, so 

 that there is no yellow or red precipitate formed, as tlie 

 ammonia holds the oxide in solution. The reduction 

 is com})lete when the blue colour disa})})ears. lo cc. 

 Pavy's Fehling=i cc. rehling = 5 milligrams of dex- 

 trose.] 



(/.) Read ofl" the number of cc. of dihde 

 urine employed. If i8 cc. were used, this, of 

 course, would represent 1.8 cc. of the original 

 urine. 



(g.) Make a second determination, using the 

 data of the first, and in this case run in at once 

 a little less of the dilute urine than was reqidred 

 at first. 



Example.— Suppose the patient passes 8550 

 cc. of urine, then as 1.8 cc. of urine reduced all 

 the cupric oxide in the 10 cc. of Fehling's solu- 

 tion, it must contain 0.5 gram sugar; hence 



1.8 : 8550 : : .05.*. -^^—5 — ? = 237.5 grants of 



I.o 



Fio. 72.— Ficro-Sac- 



chariiiieter. sugar passed in twenty -four hours, 



3. Picro-Sacchariineter of G. Jolinson. 



Solutions Eequired. 



(i.) A solution of ferric acetate the colour of which is equal to that yielded 

 Dy a solution of sugar containing ^ grain per tluid ounce. 



(2.) Saturated solution of picric acid. 



(3.) Liquor potassa; (B.P.). 



{a.) Measure i fluid drachm of urine into the boiling tube, add 30 minims 

 of liquor potassae and 80 minims of the saturated solution of picric acid. 

 Make up to the 4-drachm mark on tlie tube with distilled water. Boil for 

 one minute. 



