Oji Sal Nitrtim and Nitro- Aerial Spirit 113 



It is not easy to know whether air of this kind is 

 really common air or not, but this is certain, that it 

 will expand like air upon the application of a gentle 

 iheat, and when cooled again will contract. Nay, this 

 :air is endowed with elastic force no less than common 

 air, as I ascertained by the following experiment. 



Let a small glass tube of the diameter of a goose 

 quill and about four inches long, be hermetically 

 sealed (as chemists say) at one end ; then let a single 

 drop of water be dropped in iby the other and open 

 end, and let it be marked on a paper attached to the 

 outside of the glass how much of the space of the 

 glass the drop occupies ; then let a second drop, and 

 then others be dropped into the glass in the same 

 way as the first, and let the space occupied by them 

 b)e marked on the aforesaid paper. This done, let the 

 •open end of the glass be fitted into the narrower 

 opening of another glass open at both ends, and then 

 let that opening be carefully closed with suitable 

 •cement, as is shown in Plate V., Fig. 5. Let the glass, 

 when prepared in this manner, be so submerged in 

 water contained in a suitable vessel that, when its 

 orifice is turned upwards, all the air may pass out and 

 water enter in its place, great care being taken that 

 the narrow glass be also filled with water. Then let 

 the glass filled with water be inverted and let it rest 

 on the bottom of the other vessel, and let things 

 remain in this condition. 



And now the aforesaid air is to be transferred to 

 this glass in the following manner. Let a small dish, 

 big enough however to receive the mouth of the 

 vessel containing the air, be placed under that vessel. 

 Next let the small dish filled with the aforesaid Hquid, 

 together with the inverted glass, containing the air, 

 resting upon it, be transferred to the vessel in which 



H 



