On Sal Nitriim aud Nitro-A'erial Spirit 45 



sulphur and salt, fixed or volatile, are particularly 

 adapted for producing fermentation. Of this kind 

 are yolk of egg and all sorts of gall of animals, as 

 also soap — all of which when mixed with any farina- 

 ceous mass make it swell and ferment in cooking. 

 But the fermentative nature of the things named 

 seems to be due to this, that in cooking, the nitro-aerial 

 particles of the fire meet their saline-sulphureous par- 

 ticles and effervesce with them. 



I add further, that the glow or warmth which 

 arises in nearly everything when fermenting, appears 

 to be caused by nitro-aerial spirit, as has been already 

 indicated. For I think it is clear, from what has been 

 said elsewhere, that a most intense and fiery heat 

 proceeds from nitro-aerial particles when thrown into 

 very rapid motion. And indeed we must suppose 

 that heat of every kind depends upon the same 

 particles when briskly agitated, for heat and fire 

 must be supposed to result from the agitation with 

 different degrees of motion of the same kind of 

 particles. For in glowing substances of all sorts the 

 presence of nitro-aerial particles is shown by suffi- 

 ciently clear signs. 



As to the heat resulting from fire and from the 

 fermentation of things, it has now been shown that 

 it is caused by the motion of nitro-aerial particles. 

 As to the heat of antagonistic salts when mixed 

 together, we must imagine that it too is caused by 

 nitro-aerial spirit. For it has already been shown 

 that acid and corrosive liquids are produced by the 

 action of nitro-aerial particles, and that nitro-aerial 

 spirit resides in them as in a fitting subject ; although 

 I shall endeavour to show below that the heat pro- 

 duced by the fermentation of contrary salts depends 

 also upon nitro-aerial particles supplied by the air. 



