126 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. 



empty desiccator may be used), and in the dish 5 cc. of water 

 containing a few drops of hydrochloric acid to absorb the 

 ammonia. Let stand for forty-eight hours. Show the pres- 

 ence of ammonia in the water in the usual manner (by means 

 of platinum chloride or Nessler's reagent) . 



VI. Detection of Potassium Iodide. 



Urine, voided after the use of potassium iodide, or one to 

 which potassium iodide (0.2 per cent.) has been added, is 

 treated with nitric acid containing some nitrous acid, a few 

 cubic centimeters of chloroform are added and the mixture 

 well shaken: the chloroform becomes colored violet. With 

 urines containing considerable indican errors may arise from 

 the formation of indigo red and indigo blue. In order to 

 exclude these, add to the solution a little starch paste and 

 shake thoroughly. At the surface of contact of the chloro- 

 form and the urine a ring of the blue starch-iodine product 

 will be formed. 



If the color is due to iodine it will be removed by the addi- 

 tion of a solution of sodium thiosulphate, while the indigo 

 color will remain unchanged. 



VII. Detection of Potassium Bromide. 



Ten to twenty cubic centimeters of urine, voided after 

 the use of potassium bromide, or one which contains 0.2 per 

 cent, of potassium bromide, are made alkaline with sodium 

 carbonate, about 3 g. of potassium nitrate added, evaporated 

 to dryness in a silver or platinum dish, and then heated more 

 strongly till the mass melts and becomes perfectly white. 

 After cooling, dissolve the fused mass in water, acidify strongly 

 with hydrochloric acid (not sulphuric acid), add some fresh 

 chlorine-water, and shake with chloroform: the chloroform 

 becomes colored yellow. 



