460 APPENDIX 



the test-tube and cylinder as directed above. Next pour off or pipette 

 urine exactly to the 50 c.c. mark. Incubate for twenty-four to forty-eight hours 

 and make up the loss by evaporation, with distilled water. After the urine has 

 cooled down to room temperature the contents of tube and cylinder are thoroughly 

 mixed (the small tube having been withdrawn with a pair of forceps), then filtered 

 to remove the sediment of yeast and then brought to the exact original volume of 

 50 c.c. with distilled water to make up the loss by evaporation. (If there should be 

 doubt as to the completion of the fermentation of the glucose a qualitative test for 

 sugar can be made.) The specific gravity is again taken and the difference between 

 this and the first reading multiplied by 0.23. Example: Specific gravity of unfer- 

 mented urine, 1.030, that of urine after incubation, 1.022. Difference, 8X0.23 = 

 1.84%. 



It is advisable to have two good urino meters, one to register from 1000 to 1025, 

 a second to register from 1025 to 1050. 



Benedict's New Method for Quantitative Determination of Sugar in Urine. 



The solution for quantitative work has the following composition: . 



Copper sulphate (pure crystallized) 18 .o gm. 



Sodium carbonate crystallized (100 grams of anhydrous salt 



will answer) 200 . o gm. 



Sodium or potassium citrate 200.0 gm. 



Potassium sulphocyanate 125 .o gm. 



5% potassium ferrocyanid solution 5.0 c.c. 



Distilled water to make total volume of 1000 . o c.c. 



With the aid of heat dissolve the carbonate, citrate and sulphocyanate in enough 

 water to make about 800 c.c. of the mixture, and filter if necessary. Dissolve the 

 copper sulphate separately in about 100 c.c. of water and pour the solution slowly 

 into the other liquid, with constant stirring. Add the ferrocyanid solution, cool and 

 dilute to exactly i liter. Of the various constituents, the copper salt only need be 

 weighed with exactness. Twenty-five c.c. of the reagent are reduced by 50 mg. of 

 glucose. 



Sugar estimations are conducted as follows: The urine, 10 c.c. of which should 

 be diluted with water to 100 c.c. (unless the sugar content is believed to be low), is 

 poured into a 50 c.c. burette up to the zero mark. Twenty-five c.c. of the reagent 

 are measured with a pipette into a porcelain evaporating dish (25-30 cm. in diameter), 

 10 to 20 grams of crystallized sodium carbonate (or one-half the weight of the anhy- 

 drous salt) are added, together with a small quantity of powdered pumice-stone or 

 talcum, and the mixture heated to boiling over a free flame until the carbonate has 

 entirely dissolved. The diluted urine is now run in from the burette, rather rapidly 

 until a chalk white precipitate forms, and the blue color of the mixture begins to 

 lessen perceptibly, after which the solution from the burette must be run in a few 

 drops at a time, until the disappearance of the last trace of blue color, which marks 

 the end point. The solution must be kept vigorously boiling throughout the entire 

 titration. If the mixture becomes too concentrated during the process, water may 

 be added from time to time to replace the volume lost by evaporation. The cal- 





