BLOOD AND LYMPH 261 



(b) Chlorides. To a small amount of the filtrate in a test-tube add a few 

 drops of nitric acid and a little silver nitrate. In the presence of chloride, a white 

 precipitate of silver chloride will form. 



(c) Phosphates. Test for phosphates by nitric acid and molybdate solution 

 according to directions given on page 59. 



(d) Proteose and Peptone. Test a smalt amount of the solution for pro- 

 teose and peptone by saturating with ammonium sulphate according to directions 

 given on page 120. 



(e) Crystallization of Sodium Chloride. Place the remainder of the filtrate 

 in a watch glass and evaporate it on a water-bath. Examine the crystals under 

 the microscope and compare them with those in Fig. 80, page 267. 



6. Test for Iron. Incinerate a small portion of the coagulum from the last 

 experiment (5) in a porcelain crucible. Cool, dissolve the residue in dilute hy- 

 drochloric acid and test for iron by potassium ferrocyanide or ammonium thio- 

 cyanate. Which of the constituents of the blood contains the iron? 



/ \ 



FIG. 77. EFFECT OF WATER ON ERYTHROCYTES. 



7. Hemolysis ("Laky Blood"). Note the opacity of ordinary defibrinated 

 blood. Place a few cubic centimeters of this blood in a test-tube and add water, 

 a little at a time, until the blood is rendered transparent. Hemolysis has taken 

 place. How does the water act in causing this transparency? Examine a drop 

 of hemolyzed blood under the microscope. How does its microscopical appear- 

 ance differ from that of unaltered blood? What other agents may be used to 

 bring about hemolysis? 



8. Osmotic Pressure. Place a few cubic centimeters of blood in each of 

 three test-tubes. Hemolyze the blood hi the first tube according to directions 

 given in the last experiment (7) : add an equal volume of isotonic (0.9 per cent) 

 sodium chloride to the blood in the second tube, and an equal volume of L io per 

 cent sodium chloride to the blood in the third tube. Mix thoroughly by shaking 

 and after a few moments examine a drop from each of the three tubes under the 

 microscope (see Figs. 77 and 150, page 473). What do you find and what is 

 your explanation from the standpoint of osmotic pressure? 



