94 



Barium nitrate was estimated by determining barium in the pure 

 water solution, barium and chlorine in the solutions containing chloride, 

 and considering the excess of barium over chlorine to be present as 

 nitrate. Again the curve was a straight line, showing an increasing 

 solubility of nitrate with higher concentrations of chloride. The solu- 

 bility of barium chloride (anhydrous) in water was found to be 5.11 

 grams in one hundred cubic centimeters of the solution; in saturated 

 barium chloride solution, 9.38 grams. 



These results all agree with the assumption that double salts are 

 formed when these salts are mixed in solution, as lead chloride-nitrate 

 and barium chloride-nitrate. 



A single instance of this kind has been noticed by other observers, 

 potassium nitrate and lead nitrate by LeBlanc and Noyes. In this 

 Instance it is interesting to note that the common ion is the anion, while 

 in the new cases here presented it is the kathion. 



These exceptions to the general rule are apparently not uncommon 

 and deserve more consideration in the text-books on physical chemistry, 

 where they are rarely mentioned at all. 



In conclusion, the author desires to express his appreciation of the 

 careful experimental work performed by Mr. R. W. Duncan, B.S., 

 at that time a student in Purdue University. 



Lafayette, Indiana, December, 1903. 



