134 



Mr. W. Sutherland. 



[July 26, 



conditions of combination. Whereas the amount of a globulin suspension 

 dissolved by a certain strength of NaCl is proportional to the original 

 concentration of the suspension, the amount dissolved by HC1 depends only 

 on the total amount of acid which has access to the suspension. Hence, for 

 acids and alkalies in place of (1), we have the relation 



9 = Be, (4) 



where B is a parameter characteristic of each acid and alkali. Mellanby 

 established the same result and shows that B does not vary with temperature. 

 The contrast between solution in neutral salts and in acids or alkalies is 

 complete. Hardy proves that a given amount of globulin reacts not with 

 equivalents, but with molecules of such acids as HC1, H 2 S0 4 , and H 3 P0 4 . 

 Similarly he finds that the molecule Ba(OH) 2 has the same solvent power as 

 KOH, NaOH, and NH 4 OH. To dissolve one gramme of globulin 10 x 10~ 5 

 gramme equivalent of alkali is required, and 18 x 10~ 5 gramme equivalent 

 of the strong acids. These results will be used in Sections 4 and 6. 

 T. B. Osborne, from 1899 to 1901, obtained similar results for the vegetable 

 globulin edestin. 



3. Formulae for the Precipitation of Globulin by Salts and by Acids. 



The first case is that in which globulin is precipitated by excess of 

 a solvent neutral salt. Let c be the concentration of the salt and p the 

 fraction which the precipitated globulin is of the total originally in solution, 

 then Mellanby's graph for (NH 4 ) 2 S0 4 * is given by the equation 



p(l+p) = 28-8(c-0152). (5) 



The values of c given by this for the experimental values of p are compared 

 with the experimental values of c in the following table : — 



Table III. 



i(fip 



10 3 c exp. 

 10 3 c calc. 



315 



447 



533 



695 



787 



858 



1000 



166 



175 



183 



192 



200 



208 



218 



166 



174 



180 



193 



202 



207 



221 



To interpret this equation, we start with the consideration of the value c of 

 c at which precipitation just begins. Two actions of the salt just balance 

 here, the solvent action and the precipitant. If, then, by increasing the 

 concentration to c, the fraction p of the globulin is precipitated, an amount 

 of solvent power proportional to c p is liberated, so the solvent power, which 

 at c was proportional to c , at c is proportional to (l+p)c Q . This implies 



* Loc. cit., p. 357. 



