1] PHYSICAL ACTION OF SOLUTIONS 73 



(3) All salts of alkalis with two atoms of metal to the molecule have 



four-thirds the osmotic action of (1) (formula, R 2 'A")', e.g. 

 K 2 S0 4 . 



(4) Salts of alkalis with three atoms of the metal to the molecule 



have five-thirds the osmotic action of (1) (formula, R B 'A'"); 

 e.g. K 3 (C 6 H 5 7 ). 



In other words, the osmotic action of groups (2), (1), (3), 

 and (4) are in the proportions of 2, 3, 4, 5. These last num- 

 bers are the Isotonic Coefficients of DE VRIES. In addition to 

 these substances, DE VRIES determined that the isotonic coeffi- 

 cient is, in the case of 



salts of earthy alkalis with 1 acid radicle ; e.g. MgS0 4 . . 2 

 salts of earthy alkalis with 2 acid radicles ; e.g. CaCL, ... 4 



In the third place DE VRIES established the law that each 

 acid group and each metal has, in all compounds, the same par- 

 tial isotonic coefficients ; the coefficient of any salt is the sum 

 of these partial coefficients of the constituent components. 

 These partial coefficients are : 



for each atom-group of an acid 2 



for each atom of an alkaline metal (Li, Na, K, Kb, Cs) . . 1 

 for each atom of an earthy metal (Ca, Sr, Ba, Mg) .... 



while of the compounds the isotonic coefficients are 



KC1 = 1 + 2 = 3, MgSO 4 =0 + 2 = 2, 



K 2 S0 4 = 2x1 + 2 = 4, MgCl 2 = + 2x2 = 4, 



K,(C 6 HA) = 3x1+2 = 5, etc. 



The determination of isotonic coefficients has subsequently 

 been extended by several authors, especially by HAMBURGER 

 ('86 and '87) and by MASSART ('89). 



The work of HAMBURGER was done upon blood corpuscles. 

 The method employed by him was as follows : In certain weak 

 solutions the haemoglobin passes out of the red blood corpuscles 

 of ox blood. The concentration at which it just began to ex- 

 trude was determined for various salts, and it was found that 

 these concentrations were usually proportional to the molecular 

 weights of the substances divided by certain whole numbers, 

 which are the same as the isotonic coefficients of DE VRIES. 



