472 PEACTICAL PHYSIOLOGY 



primary proteoses. Filter and add a drop of acetic acid ; 

 a precipitate points to secondary proteoses. 

 B. No precipitate with nitric acid, but a distinct pink Biuret 

 reaction points to Peptone. Confirm by saturating the 

 original fluid with ammonium sulphate, filtering arid 

 applying the Biuret test to the nitrate. 



When two or more Proteins are present, the following method 

 will be found very useful. 



Add a few drops of salicyl sulphonic acid to several c.c. of the 

 original fluid. A white precipitate may indicate native 

 protein or proteoses. Boil. The proteoses dissolve, 

 whereas the native protein becomes coagulated. Filter 

 hot. If a precipitate forms in the filtrate on cooling, it 

 indicates Proteoses. Filter off this precipitate and apply 

 the Biuret test to the filtrate. A rose pink colouration 

 indicates Peptone. 



III. For Fats. In watery solution fat may be dissolved as a soap. 

 The presence of this can be detected by pouring some of the original 

 fluid into about 20 c.c. of 20 per cent. H 2 S0 4 contained in a small 

 beaker, and heated to near boiling point. If soap be present a film of 

 fatty acid will form on the surface of the fluid. 



IV. The following substances should also be tested for. I. Bile 

 salts Pettenkofer's reaction ; II. Bile Pigments Gmelin's test. 



V. Urea (1). Add some fuming nitric to some of the original fluid. 

 Effervescence points to urea. 



(2) Repeat with hypobromite solution. 



(3) If 1 and 2 be positive, confirm by obtaining urea nitrate crystals. 

 To do this evaporate about 30 c.c. of the original fluid to small bulk, 

 extract residue with six times its bulk of methylated spirit, evaporate 

 this extract to dry ness, dissolve residue in 3-4 c.c. distilled water, and 

 add to the resulting fluid a few c.c. of pure nitric acid, meanwhile 

 keeping the test-tube cool by holding it under the tap. Crystals of 

 urea nitrate separate out if urea is present. Examine under micro- 

 scope. 



VI. Uric Acid. Apply Murexide test. 



VII. Blood Pigment. (1) Examine by means of the spectroscope. 

 A, the original fluid; B, the same after reduction; C, the same 

 after the addition of caustic alkali and heating. By this latter 

 method alkali haematin is formed. This itself does not give a very 

 distinct absorption band, but if a reducing agent (NH 4 HS) be added 

 to it haemochromogen is formed, which has two very distinctly 

 marked bands in about the same position as those of oxyhaemoglob. in 



