Potassium Nitrate 21 



the funnel just previous to using. This can be done 

 by pouring a test tube of hot water thru, the funnel. 

 Empty out the water. 



Filter off the crystals of potassium nitrate 

 when the solution is cold; set the crystals 

 aside. Evaporate the filtrate again until 

 reduced about one-half its volum, or until 

 crystals of sodium chlorid appear in quan- 

 tity, filter thru the Witt plate, rejecting 

 the sodium chlorid on the filter and cool the 

 filtrate to the lowest point possible to crystal- 

 lize the potassium nitrate. Filter off this 

 crop of potassium nitrate, and put with 

 the quantity previously obtaind. As both 

 crops of crystals came from a solution 

 saturated with sodium chlorid as well as 

 potassium nitrate and as sodium chlorid is 

 slightly less soluble (4 grams per 100 cc.) in 

 cold water than hot some sodium chlorid 

 crystals will have formd on the nitrate. To 

 get rid of these, dissolv the nitrate in hot 

 water, using about 50 cc. or less for every 

 100 grams of crystals, and cool in cold water 

 as was done before. Filter. The mother 

 liquor should contain all the sodium chlorid 

 and if the mother liquor adhering to the 

 crystals on the filter can be replaced by water 

 before they dry out the product will be free 

 from chlorid. Wash the crystals with cold 

 water, a drop at a time, until a few of the 



