ON THE OSMOTIC PRESSURES OF CALCIUM FERROCYANIDE SOLUTIONS. 335 



where n (= 6) is the number of ions into which the molecule is split up ; column (6) 

 gives the observed osmotic equilibrium pressure. 



TABLE IX. 



If we take into consideration the various assumptions involved in calculating the 

 numbers in column (5). the agreement between these and the observed osmotic 

 pressures is as good as could be expected, but it should be mentioned that as good an 

 agreement can be obtained if the double molecule be assumed to be split up into 

 5 ions.* 



A simple chemical formula which will express these results is 



Ca(CN) ; 

 Ca(CN)/ 



/(CN) 3 Ca 

 Fe = Fe/ V 



\(CN) 8 Ca ' 



where the ions are the four Ca and two Fe(CN) 6 , while a corresponding formula applies 

 to the strontium salt. This formula was originally proposed by ERLENMEYERf for 

 the ferrocyanides, and it is of interest to see whether, in the case of the potassium 

 salt, a similar molecule, ionised into the corresponding number of ions, namely 10, 

 will bring the calculated and observed osmotic pressures into agreement. 



Using JONES and WEST'S^ measurements of the conductivities of potassium 



* In this case the constitutional formula gives four Ca ions and one {Fe(CN),;};>. 

 t 'Lehrbuch Org. Chem.,' 1867, p. 148. 

 t ' Amer. Chem. Jour.,' 34, 1809, p. 392. 



