THE INDIVIDUAL GROUPS OF PROTEINS 445 



Preparation of Crystalline Serum Albumin. 



The globulins are removed by slowly adding an equal volume of saturated 

 ammonium sulphate to serum and stirring thoroughly ; after 4 or 5 hours they 

 are filtered off. The filtrate is treated with -2N sulphuric acid until there 

 is a permanent turbidity (10-14 c.c. per 100 c.c.). Crystals separate out as 

 the solution stands. They are filtered off, dissolved in water and recrystallised 

 by adding acid and ammonium sulphate. This is repeated several times. 



Coagulated protein is obtained from it by pouring its solution in water into 

 alcohol, washing the coagulum with water and drying with alcohol and ether. 



Properties. 



Uncoagulated serum albumin, obtained by evaporation of the 

 dialysed solution, forms an amorphous yellowish mass. It is soluble 

 in water and its solution is coagulated by heating when acidified with 

 acetic acid. It shows all the general reactions of the proteins. 



Coagulated serum albumin forms a white amorphous powder 

 which is insoluble in water and salt solutions. It is dissolved by dilute 

 acids and alkalies on warming and is hydrolysed into derivatives. It 

 is more resistant to acids than egg-albumin. 



Protein Content of Serum. 



The total amount of protein in blood serum varies considerably. 

 Hartley 1 found that bovine serum contained from 6-9 per cent, and that the 

 relative amounts of the three proteins varied, but that the composition in 

 protein of the serum of a healthy animal remained constant for periods of 

 1 1 -2 1 days. In disease, the total amount was found to diminish, the 

 amount of albumin varied little, but the amount of euglobulin diminished 

 considerably. Albumin formed 37-50 percent., euglobulin 21-31 per cent, 

 of the total proteins in healthy animals ; in diseased animals the euglobulin 

 diminished to 10 per cent, and less. 



Hartley refers to observations by other workers and gives the following 

 method of estimation. 



Estimation of Coagulable Proteins in Blood or Serum. 



The blood is defibrinated and centrifugalised. 



Total protein is estimated by adding 10 c.c. of blood to 190 c.c. of distilled 

 water, acidifying the solution and coagulating by heat. The precipitate is 

 filtered off, washed with water and alcohol, dried at 100 and weighed. 



Albumin is estimated by adding 10 c.c. of blood to 90 c.c. of distilled water 

 and half-saturating the solution with 100 c.c. of saturated ammonium sulphate. 

 An aliquot portion of the filtrate is acidified and boiled. The coagulum is 

 filtered off, washed with water, alcohol and ether, dried at 100 and weighed. 



Pseudoglobulin is estimated by adding 10 c.c. of serum to 20 c.c. of 

 distilled water ; 10*5 gm. of sodium chloride are slowly added and the volume 

 is made up to 100 c.c. with saturated sodium chloride solution. The pre- 

 cipitate is filtered off after 4 hours. An aliquot part of the filtrate is acidified 

 and boiled. The coagulum is filtered off, washed with alcohol and ether, 

 dried at 100 and weighed. 



The globulin is estimated by calculating the difference. 



'" Memoirs of the Department of Agriculture in India," 1914, Vol. I, No. iv. 



