Laboratory Fractionating Columns' By J . B. Hill and S. W. Ferris ?-tis AILINTIC RGYSNCNO C o . , P ~ I A D X L P H IFAA,
( ' 1 E X ' ~ l H C inyestigabeen to produce all of the The popular designs of laboratory fractionating coltors hold widely differcondensation at the top of the umns are shown to have lower efficiencies than packed column in order to obtain the oit opinions of the relacolumns of the Hempel type with selected packings. benefit of the total quant.ity The Snyder floating hall column and the packed coltiyc efficiencies of Inbornof reflux through its entire tony irnct,ionat,iirg columns. umn with iron jack-chain show up surprisingly well length. The emphasis, thereThis i;onditim has a r i s e n . in a comparison of efficiencies. The superiority of the fore, is put on designing a Snyder over the jack-chain is sosmall that the elahorate largely, from the h c t that column which will produce the wlmnns are used under glass blowing for the former is Rcarcdy warranted. maxinium contact between ~iiferentconditions of rat,e of A method is described which may serve for an acculiquid and rapor, resulting rate comparison of efficiencies in further similar work. ilistillntiori, temperature, eto., in a closer approaoh to equiwliicli may itlter, to n large Ibriurn conditions at each Doint in the column. cstent, their relative values. Alt~irouglimttny comparisons of columns have been made,% ?'lie prWaknt forms of laboratory fractioii:it,iiig api,aratoa each has heen conducted under a set oE arbitrary conditions ,,ire their eflicicricies to two distinct principles: in which the reflux has been allowed to take care of itself, 1 ~ On ~ - beinw subiccted to gradual condensation, ulrdfr such with no attempt to equalize it for the various tests. The purpose of the present work was to compare columns in such n way t,liat their ability to produce contact betweeii liquid and vapor, as affected by the design, would be the only factor enteriuy; int.o their relative efficienc.ies. This has been done by providing the column with pract.ically perfect thermal insitlnti(ni, riirming t.he vapor through it, a t a constant rate, and ireding hack tit t.he top a constant, carefully controlled :imoniit of ~ e f l i i ~ .
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Apparatus and Procedure
The form of apparatus is shown in Figure 1. It consisted n 3-Mer flask, supported over an electric heater and connected directly with the coliirnri t,o he tested. The flask was provided witb a tube to permit sampling oE the liquid during a test. The column was tliermally insuiated in accordance with the scheme outlined by Peters.' (if
This consists .of a glass tube immediateiy s u r r o u il d i n p t h e
a larger g l a s s t u b e . through which is passed hcatcd air. The air in this outer iarket mav i>c heated iurtller I& internal electrical resistance wires. In the authors' opinion thix scheme is far superior to other forms 01 thermal irisrilation for this type of work. By its use a column can be m a d e p r a c t i c a 11y adiabatic. ~
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.is demar~dcliiive lieen iiiade for increased fractionating efficiency in thc laboratory, the second has been recognized :is the more important of these principles. The trend has b
~rescrttedbciore the Division of Organic Chemistry a t '.he 72ed MeefChemical Society, Pldadeiphia, PI., SeDtember 5 to 11.
iiig 01 the American
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Above the column was the vapor separating device, shown detail in Figure 2. It consisted of a glass tube carrying the
~ .inn., ~ m, ~ i (1884); ~ ciaudoo. , R ~ I I .
