PROTEINS 151 



the presence of strong alkalis, whereby there is formed more or less 

 alkali albumin which is not coagulated by heat. 



We have discussed these questions separately in order that we may 

 obtain a picture of the complicated relations which also reappear in 

 the other properties of albumin. 



Heat coagulation involves two overlapping processes; albumin be- 

 comes insoluble and it flocculates. WOLFGANG PAULI and H. HAND- 

 OVSKY demonstrated this very simply: a mixture of albumin with 

 2 normal KSCN was boiled and a portion of it dialyzed against run- 

 ning water. The control portion remained clear, but the portion from 

 which the KSCN was removed by dialysis showed marked flocculation. 



A further influence exerted by neutral salt upon amphoteric al- 

 bumin is the change in viscosity, the internal friction. Although 

 NaCl, NaSCN, Na 2 S0 4 , CaCl 2 and KSCN in concentrations of 0.01 

 to 0.05 normal raise the viscosity of water, they depress that of 

 amphoteric albumin solution. If the salt concentration rises, the 

 diminution in the viscosity of albumin may finally be exceeded by 

 the increase in the viscosity of the water, as occurs in fact at 0.1 

 normal NaCl and (NH^SCX Closer observation reveals a far- 

 reaching parallelism between the influence of neutral salts on heat 

 coagulation and viscosity. 



If non-neutral salts, or salts strongly dissociated hydrolytically, 

 (Na 3 PO 4 , NaHCO 3 , A1C1 3 ) are allowed to act on amphoteric al- 

 bumin, the result is quite different, since even minute traces of acid 

 or alkali form acid or alkali albumins, which behave quite differently, 

 as we shall see. With higher salt concentration the albumin is salted 

 out or flocculated. Neutral salts of the alkalis as well as magnesium 

 cause a reversible salting out such as occurs also with salts of the 

 alkaline earths, though after a very short time an irreversible coagu- 

 lation sets in. Some of the salts of the heavy metals cause an im- 

 mediate irreversible coagulation. With the alkali salts, the cations 

 (Li, K, Na, NH 4 ) do not materially differ in their salting out action, 

 but the anions do, as may be seen from the following table of F. 

 HOFMEISTER. The figures refer to the onset of turbidity in egg 

 albumen containing globulin but according to LEWITH apply also to 



OX Serum: Mols per liter 



at 30-40 C. 



Sodium citrate . 56 



Sodium tartrate . 78 



Sodium sulphate 0. 80 



Sodium acetate 1 . 69 



Sodium chlorid 3 . 62 



Sodium nitrate 5.42 



Sodium chlorate 5. 52 



lodid and sulphocyanate do not cause precipitation. 



