1906.] The Chemistry of Globulin. 139 



with p m , we should compare with p m referred to equal mass of globulin for 

 each salt. In a broad way a tends to be proportional to p m . 



It is a striking fact that though the acids HC1 and H2SO4 act by 

 equivalents in each case, the same number of equivalents is not required 

 in different cases ; in other words, a for different solvents and a constant 

 amount of globulin is not a constant, although with pure globulin these 

 acids react in definite proportions. It seems, indeed, as though the 

 precipitate we are now discussing cannot be pure globulin. So it is note- 

 worthy that the amounts of acid required to yield p m are nearly proportional 

 to the cube of the total globulin strength in each of the above four cases, 

 for, taking the values of 10b from Table V and dividing them by the cubes 

 of the relative globulin strengths given above, we get 25/17 3 , 45/2-1 3 , 

 40/2 3 , and 35/1-9 3 , or 5*1, 4*9, 50, and 51. It would appear, then, that the 

 equation of chemical equilibrium between acid b and total globulin G, 

 dissolved in neutral salt, is of the form 



C 3 = leb. (10) 



Here, evidently, G 3 represents the mass action amongst three globulin 

 compounds, whose amount in each case at the point of maximal precipitation 

 is proportional to the total amount of globulin present. Of these three we 

 know that two are probably the compound of globulin with acid alone and 

 the compound with neutral salt alone. The third, then, is probably a 

 compound containing both acid and salt, stable only when the other two 

 are present in excess. These compounds form by their joint action the 

 precipitate, whose rate of formation is measured by G 3 . Then in (10) kb 

 must represent the rate of action of the acid tending to dissolve the 

 precipitate, which acts in the usual way with a constant active mass. 



It is worth noting that when NaCl and MgS0 4 are the solvents, acids 

 precipitate globulin nearly equally, while when Na 2 S0 4 and MgCl 2 are the 

 solvents, acids precipitate nearly equal fractions, but smaller than in the 

 previous case. It seems as if ions of the same valency, like Na and CI or 

 Mg and SO4, can co-operate better than dyad with monad as found in Na2S04 

 and MgCl 2 . This recalls the observation of Picton and Linder, that ions of 

 different valency inhibit one another in precipitating colloids, while ions 

 of the same valency co-operate. 



4. A Theory of the Colloidal State. 



The characteristic of the colloid state is that the molecules cease to have 

 a separate existence ; they link on to one another by means of the atomic 

 electric charges, thus forming the meshes so characteristic of colloids 



