26 CHLORIDES OF POTASSIUM, SODIUM, ETC. 



quantity of finely -powdered oxide of mercury; the 

 mixture is digested for some time, dried, and ignited 

 in a covered crucible, when all the chloride of magne- 

 sium is decomposed and converted into magnesia. 



III. The chlorides are dissolved in a little water, and 

 the solution boiled for a long time with freshly preci- 

 pitated carbonate of silver, when all the chloride of 

 magnesium is decomposed. The precipitate is filtered 

 off) washed, and the precipitated carbonate of magnesia 

 dissolved out with dilute hydrochloric acid. 



IY. The solution of the bases is mixed with some 

 sal-ammoniac and ammonia in excess, and the mag- 

 nesia precipitated by phosphate of ammonia (see No. 6). 

 From the filtrate the ammonia is expelled by evapo- 

 ration, and the excess of phosphoric acid precipitated 

 by acetate of lead as a compound of phosphate and 

 chloride of lead. The excess of oxide of lead is pre- 

 cipitated by a mixture of ammonia and carbonate of 

 ammonia; the liquid digested, and the precipitate 

 filtered off. The alkalies are then obtained by evapo- 

 ration. 



Y. The chlorides are converted into nitrates by 

 heating with about six times their weight of nitric acid. 

 The solution is evaporated, the salts moistened several 

 times, digested with crystals of oxalic acid whereby all 

 the nitric acid is decomposed. 



From the residual mixture of magnesia and alkaline 

 carbonates, the latter are extracted with water. 



VI. The magnesia may be precipitated by sesqui- 

 carbonate of ammonia and ammonia, and washed with 

 the same. If potash is present in this precipitate it 

 may be dissolved out with water after ignition. 



VII. Should the three bases be in form of sulphates, 

 the process indicated in No. 4 must be adopted, or they 

 are weighed after ignition, dissolved in a little water, 

 the solution weighed, about one half poured ofi^ and 

 the remainder weighed. From one portion the mag- 



