CHAPTER XX. 

 PROTEIDS. 



Albumins and Globulins. Native proteids. 



Eg-g- white. (S.G. 1,045, Alkaline, contains 1QP- C - Proteids, one- 

 twentieth of which is globulin, arid nearly 1 P- C - salts.) 



Break an egg, decant the white from the yolk into a porcelain 

 capsule, cut into it repeatedly with scissors to break up the membranes, 

 strain through wet linen. 



Make the following solutions : 



1. Measure 5 CC into a beaker and add water to 50 cc , mix thoroughly 

 by stirring. The turbidity which results is due to the globulin which 

 is thrown out of solution by the dilution of its saline solvent. Strain 

 through mull muslin = solution egg albumin. 



2. To another solution of the same strength, unstrained, gradually 

 add with constant stirring small quantities of a 10 i xc - solution of common 

 salt until solution of the globulin is effected. Note the approximate 

 percentage of salt required to effect this solution. Strain = solution egg 

 albumin and globulin. 



Utilise both of these solutions to perform the following more char- 

 acteristic reactions, taking about 8 CC for each test. 



Coloup reactions. 



1. Xanthoproteic reaction. Add 2 drops of HNO 3 a pp forms, 

 heat increases it and produces a yellowish tint. Cool, 

 add NH 3 an orange colour results, which may constitute 

 the whole change if the quantity of proteid present is 

 insufficient to give a pp with acids or heat. (Due to 

 nitro-derivatives, Salkowski.) 



