66 



WORK OF J. N. PEARCE. 



Conductivity measurements gave us the value /ia>= 132.07. 



What has been said regarding the chlorides of calcium, strontium, and magnesium 

 applies equally well to barium chloride. The low value of H for 0.25 normal is 

 doubtless due to experimental error. (Table 48.) 



It is interesting to note that while the molecules of barium chloride have a much 

 smaller hydrating power than the other chlorides of the alkaline earth metals, as we 

 should expect from the fact that it crystallizes with but two molecules of water, the 

 ions which predominate in the dilute solutions have a relatively high hydrating power. 



70- 



Mg!N0 3 ) 2 



Ca(NO ;; ). : 



VTBa(NO : .)., 

 0.1 0.25 0.5 



Concentration 

 Fig. 25. 



0.1 0.25 



Concentration 

 Fig. 24. 



Another point is to be noted one 

 to which reference will be made later 

 in this paper. A glance at the 

 curves representing the values of 

 M and H for the three salts cal- 

 cium, strontium, and magnesium 

 chlorides will show that in each 

 case the curves for calcium chloride 

 lie above those for strontium chlo- 

 ride, while the two curves for mag- 

 nesium chloride lie above those for 

 calcium chloride. This order is just 

 the reverse of that for the atomic volumes of the three metals. Although barium chloride 

 crystallizes with but two molecules of water, the atomic volume of barium is still 

 larger than that of strontium. This may account for the relatively high hydrating 

 power of the ions of barium salts. 



The curves for the values of M and H are given in figs. 23 and 22, respectively. 



CALCIUM NITRATE. 



The mother-solution was diluted and 50 c.c. portions were taken for standardiza- 

 tion. The calcium was precipitated by means of ammonium oxalate and weighed as 

 calcium oxide. Table 49 gives the data; the curves are plotted in figs. 24 and 25. 



Nothing special need be said regarding the data for calcium nitrate, except to call 

 attention to the fact that the amounts of water combined with calcium chloride in 



