114 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. 



which the fibrin dissolved gives the biuret reaction (after it 

 has been neutralized with dilute sodium carbonate solution, 

 boiled and filtered) while the boiled portion does not. 



XIV. DETECTION OF ALBUMIN. 



1. Heat a portion of the clear, filtered urine to boiling. If 

 it remains clear and the reaction is acid, there is no albumin 

 present. If it becomes cloudy, the turbidity may be due to 

 the precipitation either of albumin or of calcium phosphate. 

 To decide this, acidify quite faintly with acetic acid: if the 

 urine then becomes clear, the turbidity is due to calcium phos- 

 phate and the urine is free from albumin ; if, on the other 

 hand, the turbidity remains and the precipitate tends to col- 

 lect in flakes on standing, the urine contains albumin. A 

 doubt can only arise when the turbidity which remains is very 

 small and uniform. In this case it may be due to the pres- 

 ence of mucin or nucleoalbumin in the urine. This is to be 

 assumed if the urine becomes cloudy even in the cold, when 

 acidified directly with acetic acid or after dilution with an 

 equal volume of water. If the urine remains clear on boil- 

 ing, but reacts strongly alkaline (a rare case), it may contain 

 albumin. In this case also the addition of acetic acid to acid 

 reaction decides the matter. 



2. Instead of acetic acid we may use nitric acid to acidify 

 the boiled urine. 



3. Add to the urine one-third of its volume of nitric acid. 

 If it remains clear (when only traces of albumin are present 

 the turbidity appears very gradually), then it is free from 

 albumin; if it becomes cloudy, the cloudiness may be due to 

 albumin or to urates, albumoses, or resin acids (after the use 

 of balsams or sandal- wood oil) . If the cloudiness remains on 

 warming, then it is due to albumin. 



4. Add one-third the volume of concentrated sodium 

 chloride solution, acidify with acetic acid to distinctly acid 



