226 



causes the amount of chloi'ine as ion in the solution to exceed the satura- 

 tion concentration of the chlorine ion in equilibrium with silver, so some 

 of the silver chloride must precipitate. Silver bromide is not affected 

 because there is no common ion in this case. 



In the following table, the ammonium hydroxide (1 : 100) solution 

 was saturated by warming with an excess of freshly precipitated silver 

 chloride. The ammonium chloride solution contained 25 grams per 100 cc. 



This table shows that the ammonium hydroxide silver chloride solu- 

 tion should be nearly saturated with the silver chloride, since large amounts 

 of the ammonium hydroxide make precipitation impossible or very difficult. 



In the following table, the ammonium hydroxide silver chloride solu- 

 tion was made by dissolving the silver chloride from 10 cc. of 0.8 N KCl 

 in 100 cc. of 10 per cent, ammonium hydroxide. This solution was then 

 diluted to 1000 with water. lOach cc. nf this solution contained 0.28 nig. 



Ammo.nium Chloride (25%) Solution Required to 



Give Maximum 

 Precipitation 



Produce a 

 Precipitate 



1 drop (good) r> drops 



1 drop (slight) 10 drops 



2 drops (slight) 20 drops 

 several drops never good 

 40 drops never g<M)(l 



One cc. of the ammonium hydroxide silver chloride solution contfiin- 

 ing 0.28 mg. chlorine gave a good precipitate when treated with the am- 

 monium chloride solution. Dilution of the ammonium hydroxide silver 

 chloride solution with water did not prevent the formation of the precipi- 

 tate. However, tlie addition of ammonium hydroxide solution made the 

 precipitation more difficult. 0.3 mg. of chlorine as silver chloride per 10 

 cc. of ammonium hydroxide (1:100) does not give a precipitate when am- 



