190 THE EAKL OF BERKELEY, MR. E. G. J. HARTLEY AND DR. C. V. BURTON: 



TABLE HA. Mean Values. 



numbers in the horizontal row included in columns 6 and 7 gives li ; the 1 Oth gives 

 the total loss of weight of solution and water, = 1 ; the llth gives the total gain, 

 including the amount of moisture found in the "dipping tube," while the 12th gives 

 the ratio of the vapour pressure of water to that of the solution and is obtained by 

 dividing the total loss by the loss of weight of the solution, = ?//!. 



Remarks on the Table. 



It will be noticed that the ratios of 1 to l for experiments with similar concen- 

 trations are in very close agreement. 



It should be mentioned that at first, in these experiments at C., a difficulty was 

 experienced in that the sulphuric acid in the first branch of the last vessel crystallized 

 out during the run. Now, the freezing-point of the hydrate H 2 SO 4 lAq is higher 

 than C., hence when the pure acid in the first branch takes up enough water 

 to form a liquid of that concentration it solidifies, but the addition of more water will 

 lower the freezing-point. The difficulty, therefore, was overcome by filling this first 

 branch, at the start, with an 85-per cent, solution of sulphuric acid, i.e., a solution 

 slightly weaker than H 2 S0 4 lAq. 



OSMOTIC EQUILIBRIUM PRESSURES. 



The equilibrium pressures were determined in exactly the same way as described in 

 'Phil. Trans.,' A, vol. 206, pp. 481-507. 



It is only necessary, before giving a table of the results, to call attention to the fact 

 that in all cases the " solution-leak correction," that is, the amount of calcium ferro- 

 cyanide which came through the membrane during the experiment, is practically 

 negligible. The amount coming through was determined by evaporating the water 

 contents of the tubes together with 100 c.c. washing water passed through the tube 

 after an interval of four days, down to a small bulk, and determining the calcium in 

 it by the oxalate method. 



It should be mentioned that the solutions act on the gunmetal of the osmotic 

 apparatus ; this was prevented by coating the metal with a varnish. 



In Table III., Column (l) gives the date of the experiment; (2) the weight 

 concentration (i.e., the number of grammes of anhydrous salt to 100 grammes of 



