148 Mr. W. Sutherland. [July 26, 



6. The Molecular Mass of Glohulin. 



In "A Dynamical Theory of Diffusion for Non-Electrolytes and the 



Molecular Mass of Albumin,"* I have sought to show how the molecular 



radius of a molecule can be found from its coefficient of diffusion, having 



previously obtained the corresponding relation reproduced as (15) in the 



present paper between molecular conductivity and radius. These two 



definite and accurately measurable velocities, the ionic and that of diffusion, 



are convenient aids in the measurement of large molecular masses. From the 



Graham-Stefan coefficient of diffusion for egg albumin the radius of a gramme 



molecule of albumin was found to be 30 cm., whence, from the percentage 



composition, the following formula is obtained for albumin, C1436H2364N359O482S15 



with a molecular mass 32,814 Now Hardy has obtained a direct 



measurement of the ionic velocity of globulin, namely, about 10~ 4 cm. per sec, 



which corresponds to a molecular or rather ionic conductivity 100 in the 



units used by Hardy, and 10 in the units of Kohlrausch. With the latter 



units (15) is transformed! to 



B* = 2S0v/fMK, (20) 



in which K is the dielectric capacity of the ion, having for globulin the value 



2 nearly, because for proteids the index of refraction which equals Kj is about 



1*4. B is the volume of the molecules in a gramme molecule of the ion, and v 



its valence. We are going to use this equation to find B for globulin, using 



Hardy's value 10 for fi. But so far v is unknown. It is the basicity of 



globulinic acid which is easily determined approximately by the facts we have 



in hand. Thus it has been shown that when NaOH dissolves globulin, half 



of it acts as a relatively strong base. Let M be the molecular mass of 



globulin, then v gramme molecules of NaOH act as a strong base with M 



grammes of globulin. But Hardy finds 10~ 4 gramme molecule of NaOH 



just dissolves 1 gramme of globulin, so 10~ 4 /2 gramme molecule satisfies the 



z;-basicity of globulin 



2xlOV = M. (21) 



With fi = 10 equation (20) gives 



B* = Uv. (22) 



For the percentage composition of globulin, we have Hammarsten's 

 determinations, with which I shall give the limiting volume of a gramme atom 

 of the elements taken from my ' Phil. Mag.' papers on molecular force. 



C. H. N. O. S. 



Percent 5271 7*01 15-85 23-32 111 



Atomic B 8 4 8 6 18 



* 'Phil. Mag.,' [6], vol. 9, 1905. 



t See " The Dielectric Capacity of Atoms," ' Phil. Mag.,' [6], vol. 7. 



