LIQUIDS AND ALLIED EXPERIMENTS. 



73 



48. The Same, Continued. — On dilution with about an equal bulk 

 of water the density was p= 1.0680 at 21°, corresponding to 9.5 grams in 

 100 grams of solution or 10.5 grams in 100 grams of water. The vapor 

 pressure was 7r' = 7r(i —0.060). 



The record of results is contained in table 29 and fig. 26 b. The march 

 of values as a whole is very regular, particularly when the daily observations 

 are replaced by weekly observations. The rates of diffusion are 



z'o = 0.00725 c.c/day or io^°k = 0.192 

 showing a normal increase of rates toward the value for pure water. 



Table 29. — Air into air through NaCl solution (10.5 grams in 100 grams water). Vessel 

 F. Constants as in table 28. p„,= 1.0680 at 21°. 



49. Diffusion of Air into Air Through CaClj Solution. — This solution 

 was prepared by putting 140 grams of approximately anhydrous calcic 

 chloride in 400 c.c. of water. Its density was found to be 1. 192 2 at 24.9° C. 

 A table of densities between 16° and 25° was computed, as before. The 

 solution actually contained about 21.4 grams of CaClj in 100 grams of 

 solution, or 27.2 grams of salt in 100 grams of water. In endeavoring to 

 obtain the vapor pressure it' above the solution, some difficulty was encoun- 

 tered. By graphic interpolation for the given concentration, the data at 0° C. 

 from Dieterici's observations should be tt' = tt (i — 0.198). The results of 

 Tammann made at considerably higher temperatures v^^ould give 7r(i —0.145) 

 for the same solution. The former result was assumed, as the temperature 

 of observation was nearer 0° C. The effect on the diffusion coefficient is of 

 no consequence. The daily observations are given in table 30 and fig. 27. 



The diffusion of air through strong solution of CaCla is not of an abnormal 

 character, except in the temperature fluctuations. The rates of diffusion 

 (obtained by a mean line passed through the observations) are 



z'o = 0.0062 c.c/day io^*'k = o.2I3 



being again much less than the normal value for the air- water system. 

 The physical pores of the liquid are thus virtually still much smaller. 



It is important to note that notwithstanding the greater concentration 

 of the calcic chloride solution, diffusion proceeds more rapidly than for the 

 weaker solution of KCl. In other words, the virtual stoppage is much more 

 effective, ccBt. par., in the case of KCl than in the case of CaClj, as far as can 

 yet be foreseen. True, it seems possible that all comparisons will have to 

 be made with the same apparatus, as each may have its own constants. 



