Dropping Funnel without Stopcock. J. 1 . _. -.... A. Mills, University oi Adelaide, Adelaide S. A,, Australia. _.____ l__l I_ I _
HE conventions! type of dropping funnel with a bored-plug T s t o p c o c k has a number of disadvantages, and funnels with.out external taps have been described [Hershberg, Organic Sptheses, Coll. Vol. 11, 129 (1943); Kobe, IND. ENG.CHEM.,ANAL. ED., 16, 641 (1944)l. The funnel shown in the figure, with m.hat, is essentially n glass needle valve, gives a flexibility and ease oi control very suitable for general Inboratory use.
Plunger A , made of sealed-off glass tubing, ts snugly in a guide tuhc and has its head ilarged somcwhat so that it may bc held ,.rmly in any position by mcans of thc tightly fitting rubber sleeve, B, which is lightly lubricated with glycerol or silicone grease. The tip of the plunger is d r a m off accurately and ground int,o the conical jet, C, which is sealcd into the base of the funnel. Tf the jet is correctly aligned and ground, t,ho plungor should give a vacuum-tight sed when pushed in, It is convenient t,o have the top opening ai the funnel offsot as a t F. A regulated flow of liquid is obtained by loosening the plunger in its socket and withdrawing it slightly. If a very oonstant rate ai flow is needed, the funnel may hr adapted to the design of Ashhurn and Frank [IND.ENG. CHEX, ANAL. En., 16, 418 (1944)l by having two holes, D and E, in the top~andjust ahove the tip, respectively. Jet C should be longer (2 to 3 cm.) in this ease to tmure SIifficient head of liquid to cause the dovice t cI function properly. Is of t.his type have several itdvaw 'he rate of flow is continuously v w sme uvcr a wide range from 1 or 2 drops per minute upwards; there is no risk of the contents being contaminated with lubricant, nor of leakage when using such reagents as liquid bromine. In addition, the funnel lends itself to easy warming-for example, by encasing in a steam jacket if it should be necessary to keep the contents hot. The dimensions of the funnel can vary considerably: the - ^ A ^ -."y.:FL.l..Ay u v L 2 L 6 ^i^..t c i" -..L":Jneedle valves are usually.. llldiur yuuuy Llilll. 111 YUYDIUr le diameter for the plunger and tl 3 mm. with an orifice ahout 1m r/ . a
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permit escape of the ink;t gas usod to sw&p oxygen from the solution. Use of the machinist's level ensures the horizontal posit.ion
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t" "_ II. U i i i l V l i ' ,"I bLLC p'"p"L"""" "L u m p""b"g,apLIa, V. R. Damerell oi Western Reserve University f c ing the preparation of this paper.
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many commercial polarogritphic accessories &re available. no device is made far holding, the capillary electrode in a vertical position to ensure reproducihlc drop rates [MiAler, 0. H., J . C h m . Education, 18, 65 (1941)l. The device described by Lykken [Lykken, Pompeo. and Weavcr, IND.ENG. CEEM.,ANAL.ED., 17, 728 (1945)l with a special vyatcr hath to hold the electrode and cell assembly, seems complicatcd and expensive to construct. The holder described below is easily constructed and convenient to use. Its flexibility permits resdy introduction of the cell into t,he usual type of water bath and subsequent adjustment of the electrode. Figure 1is an isometric drawing of the unit.
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Figure 2 is a 4-inch machinist's level mnnufactured by the Stanlcy Tool Company. The cell is placed in the water bath while the clectrode is in a raised position. The electrode holder is then lowered to a pre-
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Holder for Dropping Mercury Ele . . -. Cleveland Twist Drill Company, Cleveland, Ohio.
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was taken from an electrical appliance cord. The level shown in
Figure 2.
Electrode Holder
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