On Sal Nitrum and Nitro-Aerial Spirit 23 



CHAPTER IV 



OF THE SOURCE OF ACID LIQUIDS; ALSO OF THE 

 TERRESTRIAL PART OF THE SPIRIT OF NITRE 



That the spirit of nitre is a compound, and that it 

 is derived partly from the air and partly from the 

 earth, has been shown above. We have already 

 treated of its aerial part ; so that its terrestrial and 

 acid part remains for discussion. 



It is extremely difficult to understand how the 

 spirit of nitre originates in the earth. For earth 

 appears to possess the nature of a fixed, rather than 

 of an acid, salt. And yet it is undoubtedly true 

 that if exposed to the air it will, after some lapse 

 of time, be impregnated with nitre. But it* has 

 been shown above that the acid salt of which the 

 nitre in part consists originates in the earth. But 

 that it may be understood how the acid spirit of nitre 

 is generated in the earth, let me be allowed to pre- 

 fix some observations regarding the spirit of sulphur 

 and other acid liquids, because there exists among 

 all acid spirits a very great likeness and affinity. 



Hitherto the opinion has prevailed that an acid 

 salt of a vitriolic nature lies concealed in the struc- 

 ture of sulphur, and that from this, exhaling in the 

 deflagration of sulphur and collected in a superim- 

 posed glass bell-jar, the acid spirit of sulphur is 

 composed. But it seems scarcely probable that a 

 spirit so corrosive should reside in common sulphur, 

 which has a sweetish and by no means acid 

 taste. Nay, sulphur seems to have rather the 



