64 CHEMICAL STATICS 



albumins. Dividing this by 0.00177, we obtain the percentage 

 of albumin in the serum. It is necessary to dilute the ammonium 

 sulphate solution of albumins because the refractivity of proteins 

 in half -saturated ammonium sulphate solutions is abnormal (21). 



(c) Estimation of the globulins. 



Determine the refractive index of the serum and that of dis- 

 tilled water. Subtracting from the difference the known refrac- 

 tivity of the non-proteins and the known refractivity of the 

 albumins, we obtain the refractivity of the globulins. Dividing 

 this by 0.00229 we obtain the percentage of globulin in the serum. 

 Adding together the percentages of albumins and globulins we 

 obtain the percentage of total proteins. 



The following is an illustrative determination, employing ox- 

 serum obtained by whipping and centrifuging freshly-drawn 

 blood : 



Refractive index of the fluid obtained after acidifying with 



acetic acid and boiling (3 determinations) 1 . 33024 



Refractive index of AT/50 acetic acid 1 . 32902 



Difference X 2 0.00244 



Estimated concentration of non-proteins = fff = 1.5 per cent. 



Refractive index of the fluid obtained after precipitation of the globulins 

 and subsequent dilution: 



1st determination 1 . 35189 



2nd determination 1 . 35172 



3rd determination 1 . 35181 



4th determination 1 . 35189 



Refractive index of | saturated (NH 4 ) 2 SO 4 1 . 34932 



Differences X 4: 



1st determination 0.01028 



2nd determination 0.00960 



3rd determination 0.00996 



4th determination 0.01028 



Refractivity of the albumins: 



1st determination 0.01028 - 0.00244 = 0.00784 

 2nd determination 0.00960 - 0.00244 = 0.00716 

 3rd determination 0.00096 - 0.00244 = 0.00752 

 4th determination 0.01028 - 0.00244 = 0.00784 

 Average 0.00759 



Concentration of albumins: 



1st determination = ^ = 4.4 per cent 

 2nd determination = rf = 4.1 per cent 

 3rd determination = ff =4.3 per cent 

 4th determination = ty$ = 4.4 per cent 

 Average 4 . 3 per cent 



