784 Dynamical Theory of Diffusion for JYon- Electrolytes. 



Under the circumstances it seems to me best to express the 

 connexion between D and Bi by an empirical equation, 

 namely : — 



10 6 B*D = 6 + /<;/B3, (5) 



where b and k are constants for a given solvent at a given 

 temperature. For water at 16° G. 6 = 21, and k = 220, and 

 with these values the last row of numbers in the previous 

 tables marked "calcul." have been obtained. This empirical 

 formula gives a connexion between velocity of diffusion and 

 molecular radius for substances ranging from hydrogen with 

 a molecular mass 2 to raffinose with a molecular mass 500. It 

 makes 10 6 B3D = 21 when B* is large. For molecules of 

 large radius we have thus good reason to rely on the relation 



10 6 B*D = 21 (()) 



as approximately true. To illustrate its application we can 

 use it to calculate the molecular mass of egg albumin from 

 the value of 10 7 D calculated by Stefan from Graham's data, 

 namely 7. This makes B*=30,and B = 27,000. This is the 

 volume of a gramme-molecule of egg albumin. 



Representative minimum molecular formulae for albumin 

 obtained from chemical considerations are given in Gohnheiur's 

 Cliemie der Eiweisskorper. Hofmeister for serum albumin 

 gives C45oH 7 2oNii 6 Oi4oS 6 with a molecular weight (mass) 

 10166. For egg albumin he gives a minimum of 5378. For 

 haemoglobin Hiif ner and Jaquet assign 16669 for the minimum 

 molecular mass. From the lowering of the freezing-point in 

 albumin solutions Sabanajew and Alexandrow found for egg 

 albumin the molecular mass 14270, but the experimental 

 error due to impurities allows little reliance to be placed on 

 this estimate. Now to pass from the gramme-molecular 

 volume 27000 to the molecular mass we may proceed thus. 

 From the values of B published in previous papers of mine 

 we can estimate the limiting volume of a gramme-atom of G 

 as 8, of H as 4, of N as 8, of O as 6, and of S as 18. The 

 average percentage composition of egg albumin is C 52'5, 

 H 7-2, N 15*3, O 23'5, and S 1\5. Hence if x is the number 

 of carbon atoms in the molecule of egg albumin we have 

 the equation 



27000 



f« , 12 ( L 7-2 15-3 - 23-5 1'5\1 



and x= 1436. Thus the Graham-Stefan coefficient of diffusion 

 leads to G1436H2384N359O482S15 as the formula for egg albumin, 

 the molecular mass being 32814, which is a small multiple of 



