THE URINE. 183 



ity is 1.010). The number of cubic centimeters of the mer- 

 cury solution used to obtain the end-point of the reaction 

 expresses the amount of the urea in the urine in grams per 

 liter. If considerably less than 30 cc. is found necessary to- 

 obtain the end-point, a correction (according to Liebig) must 

 be applied. The difference between 30 and the number of 

 cubic centimeters actually used is divided by 5. This num- 

 ber represents the tenths of cubic centimeters which must 

 be subtracted from the number of cubic centimeters actually 

 used. The entire determination is to be made at least 

 twice on the same urine. It is also advisable to make 

 a determination with a fever urine, in which case the 

 detection of the end-reaction is more difficult, and the 

 greater concentration of the urine may also cause difficul- 

 ties (in the case of very concentrated urine take an equal 

 quantity of urine and the baryta mixture ; 15 cc. of the filtrate 

 then correspond to 7.5 cc. of the urine; or the urine may previ- 

 ously be diluted). A determination of urea should also be made 

 in a urine containing albumin, after removing the albumin. 



Removal of Albumin from Urine. 



One hundred cubic centimeters of urine are heated to boil- 

 ing in a porcelain dish, the reaction being kept very faintly 

 acid during the heating; if the urine is not acid, then add cau- 

 tiously a few drops of acetic acid. The albumin then coagu- 

 lates completely in large flakes. Boil gently for a few minutes, 

 let cool, pour the fluid into a 100-cc. measuring-flask, carefully 

 avoiding any loss, rinse out the dish with a small quantity of 

 water, so that the volume will not exceed 100 cc., let cool 

 completely (place in water), fill up to the mark with water, 

 and filter through a dry filter. 



Liebig's method gives approximately the total amount 

 of nitrogen in the urine expressed as urea, but with an 



