50 THE PROPERTIES OF PROTEINS 



forced to the conclusion that the same mass of albumin carries 

 many more positive than negative charges, so that the valency 

 of the positive albumin ion must be assumed to be relatively 

 high. This point can therefore be described as iso-molar with 

 reference to electric transport, and as aniso- electric with respect 

 to the albumin ions. 



c. Still further addition of acid produces purely cathodic 

 migration of the albumin, but at the same time the number of 

 neutral particles reaches a maximum, as is shown by a maxi- 

 mum in the quantity precipitated by alcohol, and a minimum 

 of viscosity, which occurs at approximately the same point. 

 The [Cl'j now exceeds i -o x io- 3 , but the [H-] is still 2 X io~ 6 . 

 Taking into consideration the equation of electrical neutrality 

 and also the strong migration to the cathode, we conclude that 

 the negative ionisation of the albumin is repressed almost to 

 extinction owing to the formation of neutral particles, which 

 indicate their existence by their precipitation by alcohol and 

 by the decrease in viscosity. The minimum osmotic pressure, 

 however, does not occur at the point c of maximum neutral 

 particles, but at an acid concentration which lies between b 

 and c, at which [Cl'] for i per cent, glutin is 3-8 x io~ 4 and for 

 albumin 57 X io- 4 (see Tables 13 and 14). The explanation 

 of this lies in the fact that the ionisation of A M +. wCl gives rise 

 to an increase in osmotic pressure which counteracts, and 

 finally exceeds, the decrease caused by the formation of neutral 

 particles. In consequence of this effect, the pressure minimum 

 lies at an acid concentration below that represented by the 

 point c. 



d. Above the point c, further quantities of acid convert the 

 remaining neutral albumin into acid albumin up to the point 

 of saturation of the albumin with acid, when a maximum of 

 ionisation represented by d is reached. The properties of the 

 acid albumin in this zone will be discussed in the next chapter. 



The rough diagrams of Fig. 7 serve to illustrate the points at 

 which the properties of acid albumin undergo change. It will 

 be easily understood from them that, with this mechanism of 

 reaction, the quantity of acid required to reach one of these 

 points depends on the albumin concentration ; it will be 



