IOO 



PHYSIOLOGICAL CHEMISTRY. 



FIG. 32. 



13. Coagulation Temperature. Prepare 4 test-tubes each con- 

 taining 5 c.c. of neutral egg albumin solution. To the first add i 

 drop of 0.2 per cent hydrochloric acid, to the second add i drop of 



0.5 per cent sodium carbonate solution, 

 to the third add i drop of 10 per cent 

 sodium chloride solution and leave 

 the fourth neutral in reaction. Partly 

 fill a beaker of medium size with 

 water and place it within a second 

 larger beaker which also contains 

 water, the two vessels being separated 

 by pieces of cork. Fasten the four 

 test-tubes compactly together by means 

 of a rubber band, lower them into the 

 water of the inner beaker and suspend 

 them, by means of a clamp attached to 

 one of the tubes, in such a manner 

 that the albumin solutions shall be 

 midway between the upper and lower 

 surfaces of the water. In one of the 

 tubes place a thermometer with its bulb 

 entirely beneath the surface of the 

 albumin solution (Fig. 32). Gently 

 heat the water in the beakers, noting 

 carefully any changes which may 

 occur in the albumin solutions and 

 record the exact temperature at which 

 these changes occur. The first ap- 

 pearance of an opacity in an albumin 

 solution indicates the commencement 

 of coagulation and the temperature at which this occurs should be 

 recorded as the coagulation temperature for that particular albu- 

 min solution. 



What is the order in which the four solutions coagulate ? 

 Repeat the experiment, adding to the first tube i drop of acetic 

 acid, to the second i drop of concentrated potassium hydroxide 

 solution, to the third 2 drops of a 10 per cent sodium chloride solu- 

 tion and leave the fourth neutral as before. 



What is the order of coagulation here? Why? 



14. Precipitation by Alcohol. Prepare 3 test-tubes each con- 

 taining about 10 c.c. of 95 per cent alcohol. To the first add one 



COAGULATION TEMPERATURE 

 APPARATUS. 



