9:3 



Double Salts in Solution. 



By p. N. Evaxs. 



In a paper presented to this Academy four years ago, the author 

 <'alled attention to numerous apparent exceptions to the rule that an 

 electrolyte is less soluble in a solution of another electrolyte with an 

 ion in common with the first than in water alone. The evidence presented 

 at that time was that many saturated solutions fail to give precipitates 

 on addition of second electrolytes having ions in common Avith those 

 already in the solutions. 



Since that time some of the cases then noted have been further 

 investigated, and it has been proved, as then suspected, that in these 

 -cases the electrolyte is more instead of less soluble in a solution of 

 a second electrolyte with a common ion than in water alone. 



The substances chosen were lead chloride and nitrate, and l)arium 

 •chloride and nitrate. The method of investigation was the determi- 

 Jiation of the solubility at zero centigrade of one compound in solutions 

 of the other of varying concentrations up to saturation, one hundred 

 cubic centimeters of the solution being used in each case for analysis. 



Lead chloride was estimated l)y determining chlorine in the solution 

 volumetrically, beginning with pure water and ending with a saturated 

 solution of lead nitrate, after saturating with lead chloride. It was 

 found that the solubility of the chloride increased with the concen- 

 tration of the nitrate, the ciu-ve being a straight line within the limits 

 -of experimental error. The solubility of lead chloride in water was 

 found to be 0.5420 grams in one hundred cubic centimeters of the solu- 

 tion; in saturated lead nitrate solution, 1.83 grams. 



The solubility of lead nitrate in solutions of lead chloride was not 

 determined, on account of the very limited solubility of the latter. 



Barium chloride was estimated by determiifing chlorine in the solu- 

 tion. It was found in this case also that the solubility of the chloride 

 increased with the concentration of the nitrate, the curve again being 

 a straight line. The solubility of barium chloride in Avater was found 

 to be 33.89 grams in one hundred cubic centimeters of the solution: 

 in saturated barium nitrate solution, 37.42 grams. 



