288 



During the evaporation, a portion of the chloride of 

 magnesium was decomposed, and water being poured on, the 

 amount of magnesia left undissolved was determined. 



To the solution, oxalate of ammonia was added in 

 excess, by which the lime was obtained ; and, this being 

 separated, the remainder of the magnesia was insulated in 

 the usual manner, by boiling with carbonate of potash, eva- 

 porating to dryness, &c. 



To check the determination of the magnesia, the follow- 

 ing method was taken. A known weight of the water was 

 boiled with excess of lime, by which the magnesium and 

 manganese were separated and replaced by calcium. The 

 amount of this latter metal (the free lime being, of course, 

 first removed by carbonic acid, boiling, &c.) was then deter- 

 mined by oxalate of ammonia, and subtracting from it the 

 calcium of the water as previously determined, the remainder 

 was the calcium which replaced the magnesium and man- 

 ganese. This remainder (the manganese being present in 

 very minute proportion) was found to be almost exactly what 

 it should be, supposing it to replace nothing but magnesium, 

 or it was to the magnesium directly determined in the ratio 

 of the atomic weights of the two metals. 



The solution, depi-ived of magnesia, lime, and manga- 

 nese, was now evaporated to dryness, and ignited so as to 

 expel the ammoniacal salts, and the residue gave the mixed 

 chlorides of potassium and sodium, with a trace of sulphate 

 of potash. The quantity of chloride of potassium in this 

 mixture was determined in the usual way, by the bichloride 

 of platinum, and the difference gave the chloride of sodium. 

 The numbers thus obtained, some spattering having occurred 

 during the expulsion of the ammoniacal salts, were looked 

 upon as only relatively true, and were corrected in the fol- 

 lowing manner. 



The chlorine and bromine having being determined, as 

 shall be presently described, as also the different metals, 



