94 63. BASES AND ACIDS AA'ITH EEAGENTS. 



HYDRO CHLORIC ACID. IICl. 36.5. 



63. Chlorides of all the metals in the list in § 43 are 

 soluble in water. Plumbic chloride is sparingly soluble 

 in cold water but readily soluble in hot. 



Reaction. — When argentic nitrate is added to a solu- 

 tion containing a chloride or hydrochloric acid, a white 

 precipitate is produced, AgCl, which, if at all abundant, 

 is collected together in curdy flakes on violently agitating 

 the mixture. This precipitate is blackened on exposure 

 to the light, is insoluble in dilute nitric acid, but is solu- 

 ble in ammonia ; from this solution it is re-precipitated 

 unchanged, on addition of nitric acid in excess. It can 

 be fused without decomposition. In contact with metal- 

 lic zinc in the presence of sulphuric acid, it is decomposed, 

 metallic silver being set free. 



Quantitative estimation. — Hydrochloric acid or chlo- 

 rine is most easily and accurately determined by precipi- 

 tation as argentic chloride, and the estimation may be 

 made either by a gravimetric or a volumetric process. 



a. Oravimetric Process. — Add the solution of argentic 

 nitrate, containing a slight excess of nitric acid, to the so- 

 lution of the chloride, heat the mixture and stir or shake 

 it vigorously to cause the precij^itate to settle more read- 

 ily, let it stand until the supernatant liquid is quite clear, 

 decant the liquid through a small filter, agitate the pre- 

 cipitate with hot water, transfer it to the filter with the 

 aid of a little water acidulated with nitric acid, wash it 

 at first with the same acidulated water and afterwards 

 with pure water, until the washings give no turbidity 

 with ammonic chloride. 



Dry the filter and its contents, separate the latter from 

 the filter as completely as possible, burn the filter on the 

 crucible cover, add the ash to the precipitate in the cruci- 

 ble, heat the whole some time with a little nitric acid, add 

 a little hydrochloric, evaporate carefully to dryness on the 



