186 Prof. Hare's improved Eudiometrkal Apparatus. 



meter, a communication between the inside of the receiver of 

 this instrument and the globe G, may be easily opened or 

 suspended at pleasure. 



The screw S serves to open or close a perforation which 

 communicates with the cavity of the receiver. 



Suppose the receiver R to be occupied by lime-water as 

 represented in the figure. Place the pedestal B over the 

 hole in the air-pump plate, which the rim of the pedestal is 

 ground to fit. On working the pump, the air of the receiver 

 above the lime-water is drawn out through the valve at the 

 bottom of the pipe p. Of course the air in the globe follows 

 it through the pipe, which leads from it into the receiver. 

 Having exhausted the globe and receiver, if the screw S be 

 so loosened as to allow the atmosphere to enter the receiver, 

 and press upon the surface of the lime-water while the globe 

 remains exhausted, the lime-water will of course rise into and 

 fill the globe. Should the receiver under these circumstances 

 be again exhausted, while by means of the flexible pipe D a 

 communication with the barometer-gauge eudiometer is ef- 

 fected, the pressure of the gas in the eudiometer being greater 

 than that of the rare medium of the exhausted receiver R, — it 

 follows that this gas will press into the globe and cause a por- 

 tion of the lime-water to descend into the receiver. In this 

 way, suppose 100 measures, by the barometer-gauge, taken 

 from the eudiometer. The valve-cock may then be closed, 

 and the screw S relaxed so as to admit the atmosphere. The 

 lime-water will rise into the globe until the pressure of the 

 gas therein be nearly equal to that of the atmosphere. By 

 agitating the globe, the carbonic acid will combine with the 

 lime in the water. When this object is effected, the residual gas 

 may be allowed to re-enter the eudiometer, where the quan- 

 tity of it may be measured, and consequently the extent of 

 the absorption known. It is not necessary that the apparatus 

 should remain upon the air-pump plate during the whole pro- 

 cess. By means of the valve which covers the perforation in 

 the pedestal, in which the pipe P is inserted, the exhaustion 

 may be sustained during the removal of the receiver from the 

 air-pump to any part of the laboratory where it may be con- 

 venient to connect it with the eudiometer. 



I have designated this instrument as a carbonicometer in 

 my text-book, to avoid circumlocution. It may however be 

 more properly called a washer of gas, than a measurer of car- 

 bonic acid. Hence the term gasilotor would be more appro- 

 priate. The employment of new names may appear pedantic 

 to some readers, but is really necessary, in order to avoid te- 

 dious, and, at times, almost unintelligible circumlocution. 



XXXII. Of 



