122 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. 



drying-paper, and moisten its inner surface with yellow nitric 

 acid such as was used in experiment 1. 



3. Make the urine alkaline with a few drops of sodium 

 carbonate and then add, with constant shaking, drop by drop, 

 calcium chloride solution until the supernatant fluid shows 

 no perceptible color or only the normal urine color. 



Filter off the precipitate, wash well, put it into a test-tube, 

 pour on some alcohol, and dissolve the precipitate by adding 

 hydrochloric acid and shaking. If the clear solution be boiled 

 it turns green to blue in the presence of bile-pigment, and in 

 the absence of this it remains uncolored. Let cool completely 

 and add nitric acid. The green color changes to blue, violet, 

 and red. According to Hammarsten a mixture of nineteen vol- 

 umes of hydrochloric acid with one of nitric acid is prepared. 

 One volume of this mixture is added to five to nine volumes 

 of alcohol and the precipitate dissolved in this: green solution 

 which gradually turns blue when bile-pigments are present. 



The Gmelin test may be doubtful or lead to errors if the 

 urine contains considerable indican. This is excluded by the 

 isolation of the bile-pigment in method 3. Moreover, the 

 test 3 often gives a positive result when test 1 does not. 



XX. DETECTION OF DISSOLVED BLOOD-PIGMENTS.! 



Take 400 cc. of normal urine. Add to 300 cc. of this 2 cc. 

 of diluted blood (1 : 10) and shake thoroughly. Reserve the 

 other 100 cc. for check tests. The color of the urine to which 

 the blood has been added would not lead us to suspect the 

 presence of the blood-pigment. 



1. Spectroscopic Examination Direct. If the bands of the 

 oxyhaemoglobin are not to be seen, add to the urine, accord- 

 ing to L. Lewin and Posner, some drops of ammonium sulphide 

 and then a few drops of sodium hydroxide solution. The 



1 Oxyhaemoglobin and methaemoglobin. 



