550 PHYSIOLOGICAL CHEMISTRY 



When the tube is ready to be put in the boiling water bath, 5 drops of acetone 

 solution 1 are added, care being taken that the acetone does not fall on the inside wall 

 of the test tube. The solution is now well mixed, the tube closed with a cotton 

 plug and boiled for 15 minutes. At the same time 3 c.c. of a solution containing 

 i mg. of pure glucose are treated in a similar sugar tube with i c.c. of half saturated 

 picric acid, 0.5 c.c. of 5 per cent sodium hydroxide, 5 drops of the acetone solution 

 and then heated in the boiling water bath for the same length of time as the un- 

 known. 



Both tubes are now cooled to room temperature, the standard made up to 20 c.c. 

 and the unknown to 10, 15, or 20 c.c., according to the depth of color. 



Calculation. For the calculation the following formula may be used: 



IT X X o.ooi X ~ X 100 = per cent of sugar in urine, in which R represents 



the reading of the unknown, D the dilution of the unknown, o.ooi the strength of 

 the standard, V the volume of urine employed and 100 the factor to convert the 

 figure to per cent. 



For example, with a reading of 15, a dilution of 15 and i c.c. of urine employed, 



the formula would work out: X X o.ooi X - X 100 = 0.225 per cent of 



sugar in urine.* 



Interpretation. The quantity of sugar in normal urine varies with the individual 

 but is very small in any case. The maximum excretion is probably about 1.5 gram 

 per day. 



Protein 



i. Scherer's Coagulation Method. The content of coagulable protein may 

 be accurately determined as follows : Place 50 c.c. of urine in a small beaker 

 and raise the temperature of the fluid to about 40 C. upon a water-bath. Add 

 dilute acetic acid, drop by drop, to the warm urine, to precipitate the protein which 

 will separate hi a flocculent form. Care should be taken not to add too much 

 acid ; ordinarily less than 20 drops is sufficient. The temperature of the water hi 

 the water-bath should now be raised to the boiling-point and maintained there 

 for a few minutes hi order to insure the complete coagulation of the protein pres- 

 ent. Now filter the urine 2 through a previously washed, dried, and weighed 

 filter paper, wash the precipitated protein, in turn, with hot water, 95 per cent 

 alcohol, and with ether, and dry the paper and precipitate, to constant weight, in 

 an air-bath at noC. Subtract the weight of the filter paper from the combined 

 weight of the paper and precipitate and calculate the percentage of protein in the 

 urine specimen. 



Calculation. To determine the percentage of protein present in the urine 

 under examination, multiply the weight of the precipitate, expressed in grams, 

 by 2. 



acetone solution is prepared by mixing i part of C.P. acetone with i part of dis- 

 tilled water. The solution should be freshly prepared at frequent intervals. 



2 If it is desired the precipitate may be filtered off on an unweighed paper, and its 

 nitrogen content determined by the Kjeldahl method (see p. 504). In order to arrive at 

 correct figures for the protein content it is then simply necessary to multiply the total 

 nitrogen content by 6.25 (see p. 345). Correction should be made for the nitrogen content 

 of the filter paper used unless this factor is negligible. 



