URINE: QUANTITATIVE ANALYSIS. 409 



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. 



Practically all the methods the technique of which includes eva- 

 poration at an increased temperature, either under atmospheric 

 conditions or in vacuo are attended with error. 



2. Calculation by 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 one 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 1 1 20 c.c. and the specific gravity 1.018, the calculation would 

 be as follows : 



(a) 18 X 2.6 = 46.8 grams of solid matter in i liter of urine. 



,, s 46.8 X 1 120 , -. , . 



(b) -=52.4. grams of solid matter in 1120 c.c. of 

 1000 



urine. 



Long's coefficient was determined for urine whose specific grav- 

 ity was taken at 25 C. and is probably more accurate, for con- 

 ditions obtaining in America, than the older coefficient of Haeser, 

 2-33- 



