Potassium Nitrate 23 



tubing, and a pinchcock to help regulate the 

 pressure. The proper use consists in ar- 

 ranging the apparatus, starting the pump, 

 emptying the mixture on the filter, closing 

 the rubber tube with the pinchcock and 

 then shutting off the water. As the vacuum 

 in the flask is relieved it can be increased by 

 starting the pump and momentarily opening 

 the pinchcock. Too much use of the pump 

 is to be avoided. 



It is only in exceptional cases where potas- 

 sium nitrate is of agricultural importance. 

 True, it contains both potash and nitrogen in 

 one compound and therefore in concentrated 

 form, but these substances are as well sup- 

 plied in agriculture by the sodium nitrate and 

 the potassium chlorid separately. In isolated 

 localities where the freight rate is exception- 

 ally high it is possible that the cost of manu- 

 facture of potassium nitrate would be less 

 than the freight on the sodium chlorid elimi- 

 nated in the process. In such a locality it 

 might be desirable to use potassium nitrate 

 for fertilizer. 



The classic use of potassium nitrate is for 

 black powder. Sodium nitrate being hygro- 

 scopic does not make a powder suitable for 

 use in fire arms; however a coarse blasting 

 powder is made from it, the large grains 

 being glazed to keep out moisture. 



