226 



causes the amount of chlorine 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. 



Ammonium Chloride 25% REQriRED to 



Produce a Give Maximum Redissolve 



Precipitate. Precipitation. Precipitate. 



1 drop 5 drops 12 ce. 



1 drop 5 drops 20 cc. 



1 drop 10 drops 



5 drops 



1 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 O.S N KCl 

 in 300 cc. of 10 per cent, ammonium hydroxide. Tliis solution was then 

 diluted to 1000 with water. Each cc. of this solution contained 0.28 nig. 

 of chloride. 



Cc. of Ammonium Cc. of Ammonium 

 Hydroxide Silver Hydroxide 



Chloride Used. :100) Added. 



Ammonium Chloride (25'^6) Solution Required to 



Produce a 

 Precipitate 



Give Maximum 

 Precipitation 



n drops 

 10 drops 

 2(1 (Imps 

 never good 

 never good 



1 drop (good) 



1 drop (slight) 



2 drops (slight) 

 several drops 

 40 drops 



One cc. of the ammonium liydroxide silver chloride solution contain- 

 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 formtition of the precipi- 

 tate. However, the addition of ammonium hydroxide solution iniide the 

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

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



