8/12/2019 Modified Hershberg Stirrer .pdf

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Modified Hershberg StirrerThe Hershberg stirrer is very effective far agitating light slurriesGrignard reactions) and maderately viscous liquids 1, 2). This stirrerdoes not appear to he commercially available and consequently is ofLocal construction. A reproduction of a published drawing 1 , 2) isshown as A with a portion of th e right half two loops) omitted. Other

laops may he added to the upper glass ring and the re usually is addi-tional bracing, which is not shown. There is a limit to bracing if theloops are to he tilted to permit insertion of the stirrer inta a narrow-necked flask. The Hershberg stirre r can he constructed in a variety ofshapes to fit th e contour of the flask. The original Hershberg stirr erwas constructed from glass tubing and no. 18 B. S. Nichrome o rChramel wire. For extremely viscous liquids polyphosphorie acid atroam temperature) heavier Nichrome or Chramel wire no. 16 is re- A Bquired to overcame bending and a t times wrapping the wire laops around t he shaft during vigorous stirring. Thisadditional stress frequently resulted in a broken stirrer with the glass laops being particularly vulnerable. Tostrengthen t he stirrer, massive pa i n of buttons upper pair shown as horizontal stipple and lower pair as diagonalstipple of B) were fused at 1800nta the stir ring shaf t ground rod 12.5 or 19 mm diameter with B d rawn to scale for a12.5 mm shaft) in place of the glass circles. The wire portion of the stirrer B is constructed by: a) Selecting th eappropriate length of Nichrome or Chrome1wire and preparing half of the stirrer loops usually hree or four),as shownfor the right half o fB , and curved to fit the contour of the flask. b) Attaching the pa rt constructed above to the st irri ngshaf t using the lower set of buttons as an anchoring point. The wire is woven around the shaf t as illustrated with theupper set of buttons of B. c) Repeating steps a an d h using the upper set of buttons of B. Ace Glass Inc. adapterscatalog no. 5030B an d no. 8065 ar e suitab le for the 12.5-mm and 19-mm shaft, respectively) may be used to attach th estirring shaft to a flask.These changes result in a sturdy device that retains the stirring characteristics of A. In contrast to A, the rigidattachment of th e wire loops to the stirring shaf t of B prevent its introduction inta a narrow-neck flask. Wide-mouthflasks of local mn s t ~ d i o nr commercial ones AceGlass Inc., reaction flask no. 6476) are used instead.

Literature.Cited1.H e r s h b ~ B Ind Eng.Chcm Anal Ed 19M 8 313.2.Piehex R S Ow.Synfk. dl Vol 2 Wiley:New York 1948,pp 116-119.

M. D. Cagle, T.T. Denton, and E.J. EisenbraunOklahoma S tate UniversityStillwater, OK 74078

718 Journal of hemical Education