360 ANALYSIS OF URINE. [CH. xm. 



To each tube add 2 cc. of the one per mille starch, commencing 

 with tube 10. Mix the contents by agitation and place in a thermo- 

 stat or a water bath at 38 C. for exactly 30 minutes. 



Remove the tubes and place them in a beaker of cold water for 

 3 minutes to cool. 



Arrange the tubes in order in a stand. 



Commencing with tube I add I drop of the N/5O iodine to each 

 tube and carefully note the colour produced. 



Should a colour be produced and it rapidly fades, add i more 

 drop of iodine to each tube. 



Note the tube with the lowest number that shows a blue tinge. 

 The next lower tube contains an amount of urine that completely 

 digests 2 cc. of o-i per cent, starch in 30 minutes at 38 C. 



Calculation. This is explained on page 192. The d values corresponding 

 to the volumes of urine required are given in the table. Thus if tube 4 shows a 

 bluish tint and tube 3 a red, then d 6-6. 



NOTES. i. It is customary to use a freshly prepared oi per cent, 

 solution of starch in water and to make the volume of the urine up to i cc. 

 with i per cent, sodium chloride. The author has determined that 2 per cent, 

 starch in 10 per cent, sodium chloride is quite stable and that the results 

 obtained agree with these found by the original method. It is suggested 

 that the present more convenient method be adopted as a standard. 



38 



2. The d 7 of normal urine varies between 5 and 20, with an average 



of 10. In acute pancreatitis the value is high and may be over 200. In such 

 cases the urine is still further diluted to i in 100 and the d calculated. 



2 



Thus if O'Oo6 cc. of urine is required d = ^ = 333. 



3. It is important that the same amount of iodine be added to each tube. 

 Very uneven results are obtained if varying amounts of iodine be employed. 



4. Samples of the mixed 24 hours' specimen should be used. 



5. The diastase in the urine is quite stable if the urine be preserved by 

 the addition of toluol. 3 cc. are ample for an estimation. 



6. The pipettes for measuring the solutions must be accurate i cc. 

 pipettes graduated to i/ioo cc. 



7. The end of the pipettes that are placed in the mouth should be guarded 

 by plugs of cotton wool, to prevent contamination of the fluids with saliva. 

 Bewildering results in class work disappeared after this precaution was 

 rigorously enforced. 



