268 PHYSIOLOGICAL CHEMISTRY 



on page 105. Note the temperature at which a cloudiness occurs as well as the 

 temperature at which coagulation is complete. 



2. Precipitation by Alcohol. To 5 c.c. of serum hi a test-tube add twice the 

 amount of 95 per cent alcohol and thoroughly mix by shaking. What is this pre- 

 cipitate? Make a confirmatory test. Test the alcoholic filtrate for protein. 

 Explain the result. 



3. Proteins of Blood Serum. Place about 10 c.c. of serum in a small evapo- 

 rating dish, dilute with 5 c.c. of water and heat to boiling. At the boiling-point 

 acidify slightly with dilute acetic acid. Of what does this coagulum consist? 

 Filter off the coagulum (reserve the filtrate) and test it as follows : 



(a) Millon's Reaction. Make the test according to directions given on page 



97- 



(b) Hopkins-Cole Reaction. Make the test according to directions given on 

 page 98. 



4. Sugar in Serum. To 5 c.c. of the neutralized filtrate from Experiment 3 

 add 5 drops of Fehling's solution and boil one minute. What do you conclude? 



5. Detection of Sodium Chloride. (a) Test a little of the filtrate from Ex- 

 periment 3 for chlorides, by the use of nitric acid and silver nitrate, (b) Evapo- 

 orate 5 c.c. of the filtrate from Experiment 3 in a watch glass on a water-bath. 

 Examine the crystals and compare them with those reproduced hi Fig. 80, p. 267. 



6. Separation of Serum Globulin and Serum Albumin. Place 10 c.c. of 

 blood serum in a small beaker and saturate with magnesium sulphate. What is 

 this precipitate? Filter it off and acidify the filtrate slightly with acetic acid. 

 What is this second precipitate? Filter this precipitate off and test the filtrate 

 by the biuret test. What do you conclude? 



in. Blood Plasma 



1. Preparation of Oxalated Plasma. Allow arterial blood to run into an equal 

 volume of 0.2 per cent ammonium oxalate solution. 



2. Preparation of Fibrinogen. To 25 c.c. of oxalated plasma add an equal 

 volume of saturated sodium chloride solution. Note the precipitation of fibrin- 

 ogen. Filter off the precipitate (reserve the filtrate) and test it by a protein color 

 test (see page 97). 



3. Effect of Calcium Salts. Place a small amount of oxalated plasma in a 

 test-tube and add a few drops of a 2 per cent calcium chloride solution. What 

 occurs? Explain it. 



4. Preparation of Salted Plasma. Allow arterial blood to run into an equal 

 volume of a saturated solution of sodium sulphate or a 10 per cent solution of 

 sodium chloride. Keep the mixture in a cool place for about 24 hours. 



5. Effect of Dilution. Place a few drops of salted plasma hi a test-tube and 

 dilute it with 10-15 volumes of water. What do you observe? Explain it. 



IV. Fibrin 



i. Preparation of Fibrin. Allow blood to flow directly from the animal into 

 a vessel and rapidly whip it by means of a bundle of twigs, a mass of strong cords, 

 or a specially constructed beater. If a pure fibrin is desired it is not best to 

 attempt to manipulate a large volume of blood at one time. After the fibrin has 

 been collected it should be freed from any adhering blood clots and washed in 

 water to remove further traces of blood. The pure product should be very light 

 in color. It may be preserved under glycerol, dilute alcohol, or chloroform water. 



