1906.] The Chemistry of Globulin. 145 



capacity K, and charge e, moving through water of dielectric capacity K and 

 viscosity r\ the formula is — 



fi = ve 2 K /Q7rrjaK', (15) 



that is to say, the ionic velocity is inversely as a, so that the time taken by 

 an ion under standard electric force to travel 1 cm. is proportional to a. 

 Now in the case of HC1 globulin the corresponding time is proportional 

 to 1//*, and therefore to 0'00026 + 0-009^-i Here 0*00026 represents the time 

 that would be taken by the H and the CI ions to increase their distance 

 apart by 1 cm., if they were always dissociated from the globulin. The term 

 0-009?;-* represents the time lost on account of the presence of the globulin. 

 The way in which this time is lost is the following: Suppose that HC1 

 globulin is HGC1, yielding two sets of ions HG$ and Clb, and also GClb and 

 Hf . So the H ion travels part of its path as Bf and part as HG$, while 

 the CI ion travels part of its path as Clb and part as GClb. Let r be the 

 fraction of each second which Hj and Clb spend in the forms HG and GC1. 

 During this fraction each moves with the smaller velocity %i due to the large 

 radius of G, for the rest of the second it moves with the ionic velocity u 

 appropriate to H# or Clb. The average velocity of the ion is w (l — t) + ilt. 

 Hence the time taken by the H and CI ions to separate by 1 cm. is 

 proportional to — 



= L(i+ T(i-tt/«o) y (16) 



Uq{1 — t) + UT Uq\ 1—t(1—u/uq)/' 



If, then, we write 0'00026 + 0-009^ in the form 0-00026 (1 + 34-6?;-*), 

 we have 



Tjl-uju,) 34-6^ (17) 



1 — t(1— u/uo) 



Denote r (l—u/u ) by x, then we have x/(l—x) proportional to v~%, and 



therefore to c*, where c is the concentration of the HC1. If uju is small, 



as Hardy directly proved it to be in the way we shall discuss in the next 



section, then x stands almost for t, the fraction of the total H or CI existing 



at any moment as HG#or GClb, while 1 — t stands for the amount of free 



HC1. In short, t represents the fraction of the HC1 which is combined, and 



1 — t that which is free. Hence the proportionality proved above, which 



may be written 



x = k(l-x)c\ (18) 



is an equation of chemical equilibrium expressing that the amount of 

 combined HC1 existing as HGC1 in the form of ions HG and GC1 is propor- 

 tional to the amount of free HC1 and to the amount of something else. In 

 " Ionisation, etc."* it is suggested that this something else in ordinary 



* Loc. tit., p. 173. 



