68 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. 



and exudates is very small; if it is present in considerable 

 quantities it indicates a direct connection of the fluids with 

 the kidneys or urinary ducts. 



If the test for urea in this way fails, which may happen 

 when the fluid is not quite fresh, in order to practice the 

 method add to 100 cc. of the fluid 0.1 to 0.2 g. of urea (pre- 

 viously dissolved in water). 



Under some circumstances, especially when the organs are under 

 examination (in retention of the constituents of urine), the urea 

 nitrate may be mixed with hypoxanthine nitrate : this admixture may 

 be readily detected by dissolving a weighed quantity of the urea 

 nitrate in water and adding ammonia and silver nitrate. Filter off 

 t<he precipitate, wash, incinerate, and weigh. We thus obtain the 

 weight of the silver corresponding to the amount of hypoxanthine. 

 From this the amount of hypoxanthine nitrate may be calculated, 

 and this is then subtracted from the weight of urea nitrate taken. 



V. Examination for Sugar. 



Proceed at first just as in the examination for urea, or 

 coagulate 50 to 100 cc. after the addition of a few drops of 

 acetic acid (in case the fluid contains considerable albumin it 

 is to be diluted with one or more times its volume of water), 

 filter, and concentrate, taking care that the reaction does not 

 become alkaline, by adding a few drops of acetic acid when 

 necessary. With the solution obtained, amounting to about 

 15 cc., after filtering once more, try the a-naphthol test, the 

 Trommer's test, and also the fermentation test (see in this 

 connection the chapter on Urine, " Detection of Sugar," 

 page 118). To obtain a positive result with the fer- 

 mentation test usually more than 100 cc. of the fluid are 

 necessary. 



VI. Detection of Pseudomucin (Paralbumin) in Cystic Fluids. 



1. Add to a small quantity of the fluid (about 25 cc.) some 

 drops of an alcoholic solution of rosolic acid, heat to boiling, 



