2 io Mr. Milner on the Production of 
ip. With calcined green vitriol I had much better fuccefs. 
The fait was calcined to whitenefs, and put into a gun-barrel ; 
and, after feveral trials of forcing the volatile alkali through 
the hot tube, I procured by the operation fome ounces of 
ftrong nitrous air. 
So extraordinary an effect would no doubt have proved 
highly grateful to the ancient chemifts, and have been by them 
denominated a tranfmutation. 
In the courfe of my enquiries, I confidered this experiment 
as important, becaufe it proved, that the fame combinations 
might take place when fubftances were made ufe of different 
from manganefe. 
1 8. As calcined green vitriol, per fe , in a ftrong heat yields 
dephlogiflicated air, I had now no doubt but that any fub- 
ftance which had this property might, by fimilar treatment, 
be made to afford nitrous air. 
But in this fuppofition I was entirely miftaken. The vola- 
tile alkali was applied to fome calcined alum at the moment 
when it was yielding in a ftrong heat plenty of dephlogifli- 
cated air. The product was an aftonifhing quantity of in- 
flammable air, mixed with hepatic air and adtual fulphur. The 
refidu-um of the alum had a ftrong hepatic fmell, and contained 
particles of perfectly formed fulphur. 
Mo ft of thefe experiments, if not all, were repeated in 
earthen tubes inftead of gun-barrels, and with the fame 
fuecefs. 
19. It now only remains, that I fhould briefly propofe what 
occurs to me as the probable theory and explanation of the 
facts related. 
The ingredients which enter into the composition of ni- 
trous acid leem to be the two principles or elements of the atmo- 
fphere, 
