A Simple, Versatile Weighing Tube for Reactive Liquids
4
A frequent problem in vacuum line work is the accurate weighing of liquids whieh react with air, moistme, or stopcock luhricantr. The devices suggested in most laboratory textbooks for this purpose are awkward to use, relatively heavy, and difficult to clean. A simple weighing tnhe which avoids all these problems may he construct,ed utilizing 8. Teflon Nupro valve (available from Nuclear Products Company, 15635 Saranac Road, Cleveland, Ohio) with 3fs-in. Teflon Swagdok 0.d. horosilicate tubing which is f i t h g s . The receiving tuhe may be fashioned from straight a/& drawn out in several places to allow more accurate readings a t calibration marks. If the density of the liquid is known, a rough est,imate of t,he desired amount can easily, and fairly accurately, he made. A set of standard tapeper connectors with J/s-in. o.d. ends may be constructed to allow attachment at any convenient place on thevseuum line. To handle various volumes of liquids, receiving tubes from vsrious size o.d. tubins can he const,ructed. Old burets or pipets are very useful for this purpose and avoid the necessity of volume calibrations. Far liquids whieh react with horosilicate glsss, such as int,erhalogen compounds, receiving tubes of quarts or heat, sealahle Teflon can he substituted. The Swagelok cor~nectionsare vscuum tight with only finger tightening of the cap nuts and thus allow quick assembly and disassembly so that cleaning is a simple matter. Only the valve and receiving tuhe are actually weighed. Thir is a distinct advantage when using aul.omatic halances which have little overhead space. The ilubhor and his students have med such a device regularly over the past, four years and have encountered no serious difficultieswith the valves, connectiolw, or a?semhlies.
L. SMITH WAYNIC COLBYCOLLEGI: WATEWILLE, MAINE04901
Volume
47,Number 5, Moy 1970 / 381
