32 METHODS FOR THE ANALYSIS OF URINE 



also assures one that the permanent standards have not changed 

 enough to cause inaccurate P H estimations. 



10. The distilled water may be tested at any time by adding to 

 20 c.c. two drops of the buffer phosphate solution and 1 c.c. of 

 rosolic acid, the color must be redder than the 6.65 standard but 

 not redder than the 6.8 standard. The distilled water should not 

 be too old. 



11. With these standards it is easy to make the estimations by 

 artificial light, preferably using a daylight lamp. 



12. For research accuracy it is necessary to use boiled distilled 

 water. For ordinary routine work unboiled distilled water can be 

 used, but it should be kept in a pyrex flask sealed with a rubber 

 stopper constantly except when water is being poured out. Do not 

 allow expired air to get into the flask. Excess of carbon dioxide in 

 the water can change the estimation noticeably in the case of 

 urines that are alkaline or very slightly acid. 



TOTAL SOLIDS 



1. Drying Method. Place 5 c.c. of urine in a weighed shallow 

 dish, acidify very slightly with acetic acid (1 to 3 drops), and dry 

 it in vacuo in the presence of sulphuric acid to constant weight. 

 Calculate the percentage of solids in the urine sample and the 

 total solids for the twenty-four-hour period. 



2. Long's Coefficient. The quantity of solid material contained 

 in the urine excreted for any twenty-four hour period may be 

 approximately computed by multiplying the second and third 

 decimal figures of the specific gravity by 2.6. This gives us the 

 number of grams of solid matter in 1 liter of urine. From this value 

 the total solids for the twenty-four-hour period may easily be 

 determined. 



Calculation. If the volume of urine for the twenty-four hours 

 was 1120 c.c. and the specific gravity 1.018, the calculation would 

 be as follows: 



(a) 18X2.6=46.8 gms. of solid matter in 1 liter of urine. 



,. 46.8X1120 _ . , ... 



= 52.4 gms. of solid matter m 1120 c.c. 



of urine. 



