8O PHYSIOLOGICAL CHEMISTRY. 



ALBUMINS PROPER. 



These bodies are characterized by solubility in water and in 

 weak cold acid or alkali solutions. They are readily coag- 

 ulated by heat and by shaking with strong alcohol. Although 

 usually considered as amorphous, the albumins have been 

 obtained in well crystallized form. 



The characteristic color reactions previously referred to are 

 all given by the true albumins and they are precipitated by 

 ammonium sulphate or zinc sulphate added to saturation. 

 With strong sodium chloride precipitation follows only after 

 addition of acid. 



SERUM ALBUMIN. This is the important protein body of 

 blood serum, of which it constitutes three to four per cent by 

 weight, the related substance, serum globulin, making up 

 nearly as much. While closely resembling each other, it is 

 not definitely known that the serum albumins of different 

 animals are identical. In blood the albumins are associated 

 with globulins, fibrinogen, mucoids, salts and other bodies, the 

 perfect separation of which is practically impossible. The 

 purification of serum albumin by crystallization is not easily 

 carried out with all blood serums ; in some cases the formation 

 of crystals is slow and incomplete. 



Serum albumin contains a relatively large amount of sul- 

 phur, about two per cent in the mean, and is characterized 

 further by a high specific rotation. The values which have 

 been given for this are not constant, but in the mean are about 



M^-60*. 



Crude serum albumin is now an article of commerce, being 

 made in large quantities from blood collected at the slaughter- 

 ing houses. It is usually mixed with globulin, and besides 

 is partly insoluble because of the high temperature employed 

 in drying it. For the following experiments fresh blood must 

 be used. 



Ex. Collect blood in a clean vessel and stir it thoroughly to separate 

 the fibrin and part of the corpuscles, as a clot. Some of the corpuscles, 





