POTASSIUM NITRATE 



Potassium nitrate is made by metathesis of 

 potassium chlorid and sodium nitrate, taking 

 advantage of the different solubiUties of the 

 four possible salts in hot and cold water. 



Procedure. — Heat 200 cc. of water in a 

 porcelain dish and when hot add 100 grams 

 of sodium nitrate and 90 grams of muriate 

 of potash. Evaporate until the volum is 

 reduced to about 100 cc, and filter off the 

 sodium chlorid, sand and dirt thru a 

 carefully prepared Witt filter. Throw away 

 the residue on the filter, and cool the fil- 

 trate until the crystals of potassium nitrate 

 appear in quantity. 



Some care is required to judge when the solution is 

 boild down to one-haH its original volum. If it is 

 filterd too soon, in which case few or no potassium 

 nitrate crystals separate out of the filtrate on cooling, 

 the filtrate should be evaporated further and again 

 filterd to remove the sodium chlorid which will sepa- 

 rate as solution boils away. If the mixture boils too 

 long before filtering the crystallization of the potas- 

 sium nitrate will take place in the funnel stem and 

 clog the filter. In such a case the whole mass should be 

 put back in the dish with about 50 cc. more of water 

 and reheated. It sometimes aids the filtermg to warm 



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