10 



THE ANALYSIS OF POTASSIC CHLORIDE. 



Next potassic chlorate was studied a salt which had already been 

 used by Stas for the preparation of pure potassium material. Both in 

 crystalline form and in solubility this salt is very suitable for the separa- 

 tion of sodium from potassium material. Sodic chlorate crystallizes in 

 regular crystals which are six times as soluble in hot water and sixteen 

 times as soluble in cold water as the monoclinic crystals of potassic 

 chlorate. On the other hand, the data concerning the crystalline form 

 and solubility of the chlorates of rubidium and caesium are not suffi- 

 cient to enable one to make any certain prediction with regard to their 

 behavior, and therefore experiments were made in order to discover 

 whether or not these salts could easily be separated from potassic chlorate 

 by recrystallization. The four salts of sodium, potassium, rubidium, and 

 caesium were mixed together and qualitatively separated by fractional 

 crystallization. The sodium was effectively separated from the crystals ; 

 but after three careful crystallizations the caesium line, although stronger 

 in the mother liquor than at first, was still not absent from the crystals. 

 Indeed, neither rubidium nor caesium lines had considerably diminished 

 therein. Accordingly, this method was also abandoned. 



Potassic nitrate showed itself to be much more satisfactory in its 

 behavior. Its usefulness did not seem at first so certain as to be a fore- 

 gone conclusion, especially as Stas had not succeeded in preparing a 

 particularly pure material from this salt. Probably this failure was due 

 to the circumstance that he carried out the crystallization in glass vessels, 

 which of course continually introduced sodium and silica. The rather 

 inadequate data concerning the four nitrates may be well put together 

 as follows : 



Because this series of results is not entirely conclusive, although 

 promising, a series of crystallizations was carried out here also. This 

 series showed that an admixture of the three other nitrates with a 

 large excess of potassic nitrate was nearly all eliminated by as few as 

 two crystallizations. The separation of the sodium was especially marked 



