148 The Principles of Part III. 



latile fait, viz. from the putrefied vegetable 

 and animal fubftance mixed with it. The 

 fea-falt comes from the urine of animals 

 poured on the matrix of nitre. But he 

 never could extract real nitre from this 

 nitrous earth. That cannot be done, till it 

 has got the addition of an alkaline fait by 

 itfelf, or contained in the afhes of vegetables. 

 Thefe are generally added to the nitrous 

 mafs before the water is poured on j if not, 

 they muft be added afterwards. 



THE effect: which they produce is, to 

 join with the nitrous acid, whenever a fuf- 

 ficient quantity of water is added for them 

 to act: for alkaline falts attract the acid of 

 nitre more ftrongly than the earthy bafe 

 does, and the earth is ihaked off. Hence 

 it happens, that in boiling, the liquor de- 

 pofites much of this earth. There mould 

 as much alkaline fait be added, as to fatu- 

 tate the nitrous acid fully, and fhake off 

 all the abforbent earth. The alkaline fait 



cannot 



