A HANDY MANOMETER FOR THE ORGANO-CHEMICAL LABORATORY M. Q. DOJA, SCIENCB COLLEGE, PATNA, INDIA
A small, direct-reading, and fairly accurate manometer' can be set up in the following manner. A strong bulb about an inch in diameter is blown in the middle of a piece of stout-walled glass tubing, A , having an internal diameter of about a tenth of an inchZ (Figure I). The tube is then bent as shown in Figure 11. To the bent bulh-tube is sealed another piece of glass tubing, B, of the same kind and the joint is drawn out a little. This new tube is bent twice at right angles at such points as will give the shape depicted in Figure 111. Another small tube, C, is fused to the upper horizontal portion of B to give a T and the open end of B is joined to that of A and well sealed (Figure IV). Pure dry mercury is poured into the bulb of the manometer through the tube C by means of a thistle tube provided with a ca~illarv stem until the dulb is a little more than half FLCURES V-VI1.-FILLINGAND SEALING
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A manometer somewhat similar in type has been in use in the chemical laboratory a t Cambridge, England, for some time, but the faulty method of filling gave unreliable readings and the absence of any arrangement for preventing the entrance of vapors into the manometer rendered it useless after a very short time. a This size is chosen only for its convenience: other sizes may also be used if desired. 1654
VOL.9, NO.9
A HANDY MANOMETER
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full (Figure V). The whole apparatus is then immersed in water contained in a large beaker and well exhausted3 by a Cenco-Hyvac pump connected to a standard manometer. The water is heated to boiling and the exhaustion continued, with gentle shaking of the apparatus from time to time, until the mercury in the standard manometer remains stationary a t about zero for 15 minutes. The drawn-out joint is then hermetically sealed by means of a hand blow-pipe and the position of the mercury head in the tube marked. This gives the zero point of the new manometer. After stopping the pump and allowing air to enter, the whole apparatus is disconnected and the unnecessary portions of glass tubing removed (Figure VI). The zero point ( A ) is then permanently marked by means of a good file and a millimeter scale (prepared by pasting some graph paper on a piece of thin cardboard) is attached to the manometer by wire, the zero of the scale being in line with the file mark ( A ) (Figure VII). For the sake of safety and convenience the open end of the manometer is inserted in a rubber stopper carrying a stopcock (F) provided with a side tuhe,' and the stopper is introduced into the neck of an ordinary filtering flask (Figure VIII). To ' * the open end of the manometer is attached by a piece of rubber tubing a small calcium chloride tube (H) containing a mixture of anhydrous calcium chloride and soda-lime, closed a t the other end by a cork fitted with a glass tube. The tap serves as a control for the introduction of air when the instrument is in use, and the calcium chloride tuhe prevents the entrance of moisture into the manometer-a source of constant FIGUREVII1.-THE MANOMETER MOUNTED aon USE trouble in an organo-chemical laboratory. The instrument evidently does not claim any high degree of accuracy but is sufficiently accurate for ordinary purposes. It is small in size, has a long life, is direct-reading, and requires no attention except the occasional recharging of the calcium chloride tube. These qualities, together with its simplicity, make it very useful for every-day purposes. WBELER. T. S., J. REILLY. AND W. N. RAE.Methuen & Co., Ltd., London, 1926, cf. "Physicachernical Methods." p. 371. The place of the stopcock can equally well be taken by an ordinary T-piece provided with a piece of pressure tubing and a screw clip.
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