SOLUBLE IN NITRATE OF AMMONIA. 299 



glass closed with a stopper. This glass is put in a 

 warm place for ten or twelve hours, so that all evolu- 

 tion of the hydrochloric acid may cease in the liquid ; 

 the stopper is washed, the liquid in the glass evaporated, 

 and the washing waters are also evaporated in a plati- 

 num crucible ; the water and excess of hydrochloric 

 acid are driven off, and a mixture of chloride of potas- 

 sium and sodium is obtained, which always crystallizes 

 in cubes when the chloride of sodium is in excess. 

 Sometimes these chlorides have a slight red color, 

 caused by a small quantity of nitrate left in the car- 

 bonates, but any error is prevented by heating the 

 chlorides to such a temperature as to decompose the 

 chloride of platinum formed. The chlorides become 

 black by the presence of the platinum, but this metal 

 from the vessels does not alter the weight of the 

 chlorides. 



The alkaline chlorides being weighed, a small quan- 

 tity of water is added, and some chloride of platinum, 

 if there is any potassa. The mixture of chloride of 

 platinum and alkaline salts is evaporated to a syrupy- 

 consistency, and treated with pure alcohol. The resi- 

 due consists of the double chloride of platinum and 

 potassium, and some chloride of sodium. It is dried 

 and calcined in order to reduce the platinum. The 

 chlorides of potassium and sodium are separated by 

 water; the mixture is again ignited and weighed. 

 The material which remained in the crucible is the 

 platinum which proceeds from the double chloride. 

 From the weight obtained we deduct that of the chlo- 

 ride of potassium which it contains; by subtracting 

 from the weight of the alkaline chlorides the weight of 

 the chloride of potassium, the weight of the chloride of 

 sodium is obtained. Having these weights it is easy 

 to determine that of the potassa and soda. 



The following verifications may then be made : 1st. 

 The lime which has been heated till cessation of loss 



