194 PHYSIOLOGICAL CHEMISTRY. 



pare this result with the specific gravity as determined by Hammer- 

 schlag's method in the next experiment. 



4. Specific Gravity by Hammerschlag's Method. Fill an 

 ordinary urinometer cylinder about one-half full of a mixture of 

 chloroform and benzene, having a specific gravity of approximately 

 1.050. Into this mixture allow a drop of the blood under exami- 

 nation to fall from a pipette or directly from the finger in case 

 fresh blood is being examined. Care must be taken not to use 

 too large a drop of blood and to keep the drop from coming in 

 contact with the walls of the cylinder. If the blood drop sinks to 

 the bottom of the vessel, thus showing it to be of higher specific 

 gravity than the surrounding fluid, add chloroform until the blood 

 drop remains suspended in the mixture. Stir carefully with a glass 

 rod after adding the chloroform. If the blood drop rises to the 

 surface upon being introduced into the mixture, thus showing it to 

 be of lower specific gravity than the surrounding fluid, add benzene 

 until the blood drop remains suspended in the mixture. Stir with 

 a glass rod after the benzene is added. After the blood drop has 

 been brought to a suspended position in the mixture by means of 

 one or more additions of chloroform and benzene this final mixture 

 should be filtered through muslin and its specific gravity accurately 

 determined. What is the specific gravity of the blood under ex- 

 amination ? 



5. Tests for Various Constituents. Place 10 c.c. of defibri- 

 nated blood in an evaporating dish, dilute with 100 c.c. of water 

 and heat to boiling. Is there any coagulation, and if so what 

 bodies form the coagulum? At the boiling-point acidulate slightly 

 with dilute acetic acid. Filter. The filtrate should be clear and 

 the coagulum dark brown. Reserve this coagulum. What body 

 gives the coagulum this color? Evaporate the filtrate to about 

 25 c.c., filtering off any precipitate which may form in the process. 

 Make the following tests upon the filtrate: 



(a) Fehling's Test. Test for sugar according to directions 

 given on page 27. 



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

 add a few drops of nitric acid and a little argentic nitrate. In the 

 presence of chloride, a white precipitate of argentic chloride will 

 form. 



(c) Phosphates. Test for phosphates by nitric acid and molyb- 

 dic solution according to directions given on page 57. 



(d) Protease and Peptone. Test a small amount of the solu- 



