A text-book on chemistryFor the use of schools and colleges . austed from its inte- F&216-rior, the superincumbent pressure retains theglass so firmly in contact that it is impossibleto lift it off; but when the air is readmittedit can easily be moved. If within the receiv-er a a smaller one, #, be placed, and exhaus-tion made, while a is fixed, b can be easilymoved by shaking the pump; but, on letting in the air, bbecomes fixed and a loosened. If over the mouth ofa jar, Fig. 217, placedon the pump, the palmof the hand be laid asthe air is exhausted, it ispressed in close contactwith the jar,
A text-book on chemistryFor the use of schools and colleges . austed from its inte- F&216-rior, the superincumbent pressure retains theglass so firmly in contact that it is impossibleto lift it off; but when the air is readmittedit can easily be moved. If within the receiv-er a a smaller one, #, be placed, and exhaus-tion made, while a is fixed, b can be easilymoved by shaking the pump; but, on letting in the air, bbecomes fixed and a loosened. If over the mouth ofa jar, Fig. 217, placedon the pump, the palmof the hand be laid asthe air is exhausted, it ispressed in close contactwith the jar, and canonly be removed by the exertion of a veryconsiderable force. On the small plate a, Fig. 218, furnished0, vvith a stopcock, 5, terminating in a jet, c,a tall receiver is placed, and the appara-tus being screwed on the air-pump, is ex-hausted, and the stopcock closed. Onbeing opened when the lower end of thetube dips under water, the water rises tothe top of the jar, and forms a fountain invacuo. /f^ 3jk F f H i! 1 \l « i