NOTE on the FILLING of MANOMETERS M. O; DOJA Science College, Patna, India
T
closed, and D and B are opened, the latter being connected to a Cenco-hyvac pump provided with a standard manometer. The whole apparatus is then evacuated until the standard manometer shows a minimum pressure. Freshly distilled mercury is placed in the cup, C, and the taps, B and D, are both closed. A is then very slowly opeoed and a small amount of mercury is allowed to collect in the space between A and D. The tap, A , is closed and D is gently opened so that the collected mercury slowly falls into the manometer. In this manner (which prevents a sudden rush of mercury), little by.little, the required quantity of mercury is introduced into the manometer. The manometer is finally disconnected from the apparatus and air is allowed to enter slowly through the tap, D. The manometer is then ready for use and gives quite accurate readings for ordinary purposes. The chief advantage of the method lies in its quickC ness and simplicity, as i t avoids the difficulty of elabofollowing methodfor thefilling rate sealing which is necessary in the standard method. of manometers has been de- I t also gives a much stronger sealed end than can be obtained in the other method, because the sealing is vised. done before the mercury is introduced into the maA cleaned and dried manometer is joined by means nometer. of a piece of pressure tubEqually satisfactory results are obtained by using ing to the apparatus shown screw clips and pressure tubing instead of the glass in the accompanying figure, which is simply a Y-piece taps, and an ordinary conical funnel in place of the provided with two taps and a cup. The tap, A, is cup shown in the figure.
HE standard method for the filling of accurate vacuum manometers by sealing both ends of the manometer to a suitable piece of glass tubing, boiling the introduced mercury in a vacuum until all air is expelled, and finally sealing off one end by means of a hand blowpipe, is so tedious and requires so much skiU in glass work that a simpler and quicker method seemed neces~sary. It is with this object in view that the
n
