336 



THE OSMOTIC PEESSUEES OF CALCIUM FEEEOCYANIDE SOLUTIONS. 



ferrocyanide solutions at C. and treating the results in the same way as that 

 adopted for the other salts, but keeping to their own units, we get for the double 

 molecule and 10 ions the following table, where /u,^ = 8 8 '5. 



TABLE X.- Potassium Ferrocyanide. 



The agreement between the numbers in columns (5) and (6) seems good enough to 

 warrant the conclusion that the assumption of double* molecules ionised into 10 ions 

 is not incompatible with the facts. On the other hand, it may be pointed out that 

 the deviation from the theoretical BOYLE'S law osmotic pressure may be considerable, 

 for it is apparent in cane-sugar solutions even down to some 7 atmospheres pressure ; 

 in view of the uncertainty of the value of the conductivities at infinite dilution, 

 together .with the weakness of the theory which connects them with the conduc- 

 tivities of _ the solutions themselves, it was considered useless to attempt to correct for 

 these deviations. 



Reviewing the evidence recorded in this communication, it may be concluded that 

 the calcium and strontium salts are proved to be associated when in solution, and it is 

 possible that they exist as the double molecules of the formula given on p. 335. 



* Cp. BUCHBOCK'S work on aqueous solutions of tetraethyl ferrocyanide (' Zeit. Phys. Chem.,' 23, 1897, 

 p. 157), shows the molecule to be (C 2 H 5 ) 2 Fe(CN)o. In view of the known tendency for organic iso- 

 cyanides to be formed from certain metallic cyanides, it may be that this substance is constituted 

 differently to the metallic ferrocyanides. 



