DILUTION OF CONCENTRATED SOLUTIONS. 



Table II. shows the degree of accuracy obtained. 



TABLE II. 



327 



The last value in this table shows the failure of the relation for dilute solutions, but 

 since heats of dilution at this concentration are so small, very little relative error is 

 introduced by interpolating graphically. 



The value of the constant b changes with the temperature. 



Heat of Dilution. 



All the observations were taken with the initial temperature of the solution and 

 the water that of the air. No radiation correction need be applied, since the process 

 of mixing was very rapid. In the first six experiments the smaller pipette was 

 employed, and the water equivalent 44'75 gr. ; for the next two experiments, the 

 larger pipette was used with water equivalent 4 5 '6 gr. The last two experiments 

 were performed by a pipette which was not immersed in the solution. The solution 

 and distilled water were brought to the same temperature (that of the air) by enclosing 

 the latter in a vessel immersed in the former. Quantities of each were measured out 

 in turn in experiment (IX.), 200 c.c. of solution to 100 of water, and in (X.), 150 c.c. 

 of each. The mixing process was performed in the same vessel, and the water 

 equivalent was 46 '0 gr. 



As a check on the concentration the densities of the solutions were obtained before 

 and after mixing, and the new value of concentration after the process of mixing was 

 found by application of the expression 



P , 1800 Qcd 



(1800 + cm) (Qd + x) - Qdcm 

 where c is the initial concentration in molecules of acid per 100 molecules of water, 



Q the volume of solution taken in c.c., 



d its density at the temperature employed (gr./c.c.) 



m the molecular weight here 36 '5, 



x the number of gr. of water added. 



VOL. CCXV. A. 



2 x 



