APPENDIX. 293 
1. That thefe Fumes do at the ^amc time 
both generate and abforb Air, is further e- 
vident from the following Experiment, viz. 
I placed at once under a large inverted chy- 
mical Receiver, whofe Orifice was immerfed 
in Water, five deep and wide glafs Tubes which 
were clofed at their lower ends, and bound faft 
together, and fupported at a due Height by a 
Stick in the midfl of them. There Was in 
each of the Tubes a cubic Inch of compound 
Aqua-fortis, on which I let fall at two Hours 
Diftance from each other, the powdered 
fVhitJlable Pyrites. Upon the two firrt Mix- 
tures more Air was abforbed than generated ; 
but the Effervefcences of the three following 
Mixtures generated feverally more than was 
abforbed, viz. becaufe as appears in feveral 
other Inftances, when the Air in the invert- 
ed Receiver was much impregnated with the 
fulphureous Fumes of the two firfl effervefeenc 
Mixtures, the Fumes of the three following 
Mixtures abforbing no more Air, the Quan- 
tity generated by thofe Mixtures, was feen by 
the fubfiding of the Water in the inverted Re- 
ceiver. 
5. This Coperas Stone with Oil of Vi- 
triol or Oil of Sulphur, or Spirit of Salt, each 
U 5 diluted 
