238 PHYSIOLOGICAL CHEMISTRY 



sulphate until a precipitate is obtained. Again place in the ice 

 box until the next period. On standing, the precipitate, which 

 is at first amorphous, will become crystalline. Examine under 

 the microscope. The crystals are small, and look much like sand 

 grains. If similarly prepared, serum albumin and lactalbumin 

 crystals may be obtained. 



ii. Solubility of Egg Albumin. Test the solubility of pow- 

 dered egg albumin in water and 10% HC1. Recall notes on solu- 

 bility determinations under dextrose. A filtrate may best be 

 tested for protein by one or more of the color reactions. Recall 

 that albumins are precipitated in neutral solution by saturating 

 with ammonium sulphate, but not with magnesium sulphate, or 

 sodium chloride, or on half saturation with ammonium sulphate. 

 If the solution is acid, however, in these latter cases some albumin 

 is precipitated. Recall also that albumin is coagulated by heat 

 and is precipitated by various reagents such as alcohol, mineral 

 acids, etc. 



iii. Recall the color reactions of the albumins as determined 

 under general protein tests. 



iv. Coagulation Temperature of Egg Albumin Solution. Fill 

 a large beaker half full of tap water. In this beaker place a 

 smaller beaker or an Erlemeyer also about half full of water. If 

 the inner vessel is not supported by fitting into the large beaker, 

 arrange the amount of water in this inner vessel so that it will 

 not sink to the bottom of the large beaker. Place a test tube 

 c< ntaining about five cubic centimeters of clear, fresh albumin 

 solution in the inner vessel, and add to the albumin solution 

 about 1 c.c. of saturated sodium chloride and a few drops of 1% 

 acetic acid. While your partner carefully warms the water in 

 the outer beaker, observe the thermometer and the albumin solu- 

 tion. The point at which it becomes cloudy is taken as the coagu- 

 lation temperature of the protein under examination. 



2. Globulins. As has been observed above, globulins, at least 

 those of animal origin, are precipitated from neutral solution by 

 saturating with MgS0 4 or half saturating with (NH 4 ) 2 S0 4 . 



i. Plant Globulins. Globulins are found in many plants and 



