2 Mayow 



nitre, sal nitrum seems to be composed of an extremely 

 fiery acid salt, and, in addition, of an alkali or of purely 

 saline volatile salt taking the place of the sal alkali. 

 And this may be ascertained not only from its analysis 

 but also from the way in which it is produced. As 

 regards sulphur, which nitre is commonly supposed to 

 contain, it is our opinion that although nitre defla- 

 grates readily enough when thrown into the fire, 

 still a combustible sulphur is in no wise present, as 

 will be shown below. 



If nitre is analysed by distillation, acid spirit will 

 pass into the receiver, while fixed nitre, closely re- 

 sembling sal alkali^ will be left in the retort. More- 

 over, when nitre is melted in a crucible, and sulphur 

 is thrown in repeatedly until the nitre will deflagrate 

 no longer, the substance left at the bottom is im- 

 properly called fixed nitre, since there is fixed only 

 one element of the nitre, namely, its salt ; the other 

 element, namely, the acid spirit, escaping in vapour 

 during deflagration. Still, this spirit may be retained 

 if deflagration takes place in a tubulated retort with a 

 receiver attached, or under a bell-jar. 



Further, if nitre and tartar, mixed in equal quanti- 

 ties, are kindled by ignited iron or charcoal, fixed salt 

 equal in amount to the whole of the tartar will be 

 found after the deflagration, and of this at least some 

 part is derived from the nitre, and is generally but im- 

 properly called salt of tartar ; for, since this fixed salt 

 is equal to the whole of the tartar, while the tartar is 

 not all fixed salt, but consists to a large extent of spirit 

 and a fetid oil which passes off during the deflagra- 

 tion, some part of the remaining salt must accordingly 

 be due to the nitre. 



In the same way, if we look at the mode in which 

 nitre is produced, we shall recognise clearly the same 



