OSMOTIC PRESSURES OF AQUEOUS SOLUTIONS OF CALCIUM FERROCYANIDE. 181 



1 part in 20,000. It was not considered necessary to correct for the volume of liquid 

 above the bottom of the meniscus as the error appertains to both the determination of 

 capacities and of the density. One uncertainty remains, in that when making up the 

 solution, the neck above the level has been wetted and an unknown, arid possibly 

 variable, quantity of liquid is left adhering. There is no means of correction for this, 

 but the fact that the densities of slightly differing solutions generally follow the 

 weight concentration indicates that this source of error is of no great importance. 



In the following table all the results on the densities of the solutions are given. 

 The first column gives the weight concentration, i.e., the number of grammes of 

 anhydrous salt in 100 gr. water, and the second gives the density. 



TABLE I. 



TABLE I A. Mean Values. 



LOWERING OF THE VAPOUR PRESSURE. 



During the progress of the research it was found that there was a disagreement of 

 some two or three per cent, between the direct measurement of the equilibrium 

 pressure and the same when calculated by means of PORTER'S equation from the 

 lowering of the vapour pressure of the solutions. 



The cause of this discrepancy is surmised to be due to the fact that the experiments 

 were carried out in air at atmospheric pressure, while Prof. PORTER'S equation implies 

 vacuum conditions ; and although by modifying the equation to suit our requirements 

 we obtain results (infra) which are in close agreement, yet the values for the vapour 



* This density was not used in the final computations it is known to be wrong sufficient time was not 

 given for the temperature of the solution to become constant at C. 



