70 



WORK OF J. N. PEARCE. 



HYDRATES OF BARIUM BROMIDE AND BARIUM IODIDE. 



Since the two barium salts studied are so slightly soluble, it was thought best to 

 add the tables for the hydrates of barium bromide and barium iodide which were pre- 

 pared by Jones and Bassett 1 (table 53). Both of these salts crystallize with two 

 molecules of water of crystallization. 



The solubilities of these two salts are nearly equal to those of the other halicles of the 

 calcium group. It is very probable, owing to the fact that Jones and Bassett used a 

 thermometer less sensitive than the one employed in this work, that the observed 

 freezing-point lowerings for the most dilute solutions are too low. This would, of 

 necessity, give low values for the total combined water and for the hydration. 



The values of M for these salts increases regularly with increase in concentration. 

 The magnitude of hydration for each salt is approximately constant. If we compare 

 the values of // for the four barium salts in tables 48, 52, and 53 we see that, of the 

 halicles, the iodide has the greatest hydrating power and the chloride the least, while 

 the bromide stands intermediate between the other two. The nitrate has the least 

 hydrating power. 



Since the chloride, bromide, and iodide crystallize each with two molecules of 

 water, we should expect the observed molecular lowering to be greater than the cal- 

 culated. Experimental results confirm this. 



COBALT CHLORIDE. 



An approximately 2 normal solution was first made up. A portion of this was 

 diluted to convenient strength and the cobalt determined electrolytically. 



Cobalt chloride crystallizes with 6 molecules of water, and, like the other chlorides 

 with the same amount of water of crystallization, has a large hydrating power. The 

 results are just what we should expect (table 54). 



It will be noted, first of all, that the freezing-point lowerings for all concentrations 

 are greater than for any of the salts thus far studied, and hence there is a correspond- 



l Loc. cit. 



