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Round-bottom flask
open-in-new
<h2 id="uses">Uses</h2> <ul><li>Heating and/or boiling of liquid.</li> <li><a href="/facts/Distillation/plDvUMxn">Distillation</a>.</li> <li>Contain chemical reactions.</li> <li>Distilling flask in <a href="/facts/Rotary_evaporator/451a3Tyy">Rotary evaporators</a>.</li> <li>Storage of the culture media.</li> <li>Preparation of gas-phase standards for flasks fitted with septa (requires volumetric calibration)</li></ul> <p>The round bottoms on these types of flasks allow more uniform heating and/or boiling of liquid. Thus, round-bottom flasks are used in a variety of applications where the contents are heated or boiled. Round-bottom flasks are used in <a href="/facts/Distillation/plDvUMxn">distillation</a> by chemists as distilling flasks and receiving flasks for the distillate (see distillation diagram). One-neck round-bottom flasks are used as the distilling flasks in <a href="/facts/Rotary_evaporator/451a3Tyy">rotary evaporators</a>. </p><p>This flask shape is also more resistant to fracturing under vacuum, as a sphere more evenly distributes stress across its surface. </p><p>Round-bottom flasks are often used to contain <a href="/facts/Chemical_reaction/GpqWlKrz">chemical reactions</a> run by chemists, especially for <a href="/facts/Reflux/Elav2kgM">reflux</a> set-ups and <a href="/facts/Laboratory/kqR3Vtx9">laboratory</a>-scale <a href="/facts/Chemical_synthesis/3KXsVVwC">synthesis</a>.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> <a href="/facts/Boiling_chip/YwCIIu5o">Boiling chips</a> are added in distilling flasks for distillations or boiling chemical reactions to allow a nucleation site for gradual boiling. This nucleation avoids a sudden boiling surge where the contents may overflow from the boiling flask. <a href="/facts/Stir_bar/MywqG2YS">Stirring bars</a> or other stirring devices suited for round-bottom flasks are sometimes used.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> Round bottom flasks suffer from poor stirring when compared with <a href="/facts/Erlenmeyer_flask/p2X2jrPa">Erlenmeyer flasks</a>, as they can't accept large stir bars and material can become trapped at the base. For a reflux set-up, a <a href="/facts/Condenser_(laboratory)/ITtBcchY">condenser</a> is typically attached to the middle or only neck of the flask being used. Additional necks on a flask could allow a <a href="/facts/Thermometer/almVTBxI">thermometer</a> or a mechanical stirrer to be inserted into the flask contents. The additional necks can also allow a <a href="/facts/Dropping_funnel/cYkB86Au">dropping funnel</a> to be attached to let <a href="/facts/Reactant/c3GLInCu">reactants</a> slowly drip in.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a> </p><p>Special electrically powered heating mantles are available in various sizes into which the bottoms of round-bottom flasks can fit so that the contents of a flask can be heated for distillation, chemical reactions, boiling, etc. Heating can also be accomplished by submerging the bottom of the flask into a <a href="/facts/Heat_bath/8ntaBCB6">heat bath</a>, <a href="/facts/Heated_bath/WPm0vgJA">water bath</a>, or <a href="/facts/Sand_bath/fN79VIhA">sand bath</a>. Similarly cooling can be accomplished by partial submerging into a <a href="/facts/Cooling_bath/XrxQyrEE">cooling bath</a>, filled with e.g. cold <a href="/facts/Water/0lkXnJPK">water</a>, <a href="/facts/Ice/BGvkKFjD">ice</a>, <a href="/facts/Eutectic/UFbecnqo">eutectic</a> mixtures, <a href="/facts/Dry_ice/BvW99HtH">dry ice</a>/solvent mixtures, or <a href="/facts/Liquid_nitrogen/IGWI1h00">liquid nitrogen</a>. For gas preparation where heating is required. Since the flask is round bottomed heat is uniformly distributed throughout on heating. </p> <h2 id="related-glassware">Related glassware</h2> <p class="note">Main article: <a href="/facts/Laboratory_flasks/9puakCDX">Laboratory flasks</a></p> <ul><li><a href="/facts/Flat-bottomed_flask/9puakCDX">Flat-bottomed flask</a>: A flask with similar uses as the round-bottom flask, but with a flat bottom that allows it to stand on a level surface.</li> <li><a href="/facts/Florence_flask/UWvWEKSQ">Florence flask</a>: A flask similar to the flat-bottomed flask that has round bodies and either a round bottom or a flat bottom so that one can stand the flask on a level surface. Florence flasks typically have one neck which is longer and may be somewhat wider than the usual neck of a round bottom flask. The necks of traditional Florence flasks often do not have a ground glass joint like modern round bottom flasks do. Round-bottom flasks are used more commonly by professional <a href="/facts/Chemist/N09K7Bdm">chemists</a> than Florence flasks.</li> <li><a href="/facts/Retort/lwrgFkIC">Retort</a>: A spherical vessel with a long downward-pointing neck, specially used for distillation or <a href="/facts/Dry_distillation/Eh04GWau">dry distillation</a> of substances.</li> <li><a href="/facts/Schlenk_flask/nAJ7W1I9">Schlenk flask</a>: A round-bottom flask with a built-in plug valve or <a href="/facts/Stopcock/VnwHgYGB">stopcock</a>.</li></ul> <h2 id="legality">Legality</h2> <p>In the United States, it is illegal for an individual to possess, manufacture, buy, or sell a three neck round bottom flask while knowing, suspecting or intending the flask's purpose to be the manufacture of illegal or controlled substances. It is <i>not</i> illegal, however to possess, manufacture, buy or sell a three neck round bottom flask for legal activities.<a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p> <h2 id="gallery">Gallery</h2> <table><tbody><tr><td></td><td></td></tr></tbody></table> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>"OCS Lab Equipment: round Bottom Flask." Department of Chemistry. University of Nevada. <a href="http://www.chem.unr.edu/store/glassware/rbf.html" target="_blank">http://www.chem.unr.edu/store/glassware/rbf.html</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>"OPCW Logo". OPCW. Retrieved 2020-08-13. <a href="https://www.opcw.org/media-centre/opcw-logo" target="_blank">https://www.opcw.org/media-centre/opcw-logo</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Reflux. Department of Chemistry. University of Alberta, Canada <a href="https://web.archive.org/web/20111008182253/http://www.chem.ualberta.ca/%7eorglabs/Techniques%20Extra%20Info/Reflux.html" target="_blank">https://web.archive.org/web/20111008182253/http://www.chem.ualberta.ca/%7eorglabs/Techniques%20Extra%20Info/Reflux.html</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>"Reaction Notes 2.". Chemistry Department. University of Rochester <a href="http://chem.chem.rochester.edu/~nvd/reactionnotes2.html" target="_blank">http://chem.chem.rochester.edu/~nvd/reactionnotes2.html</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Distillation. Department of Chemistry. University of Alberta, Canada <a href="https://web.archive.org/web/20111008182346/http://www.chem.ualberta.ca/~orglabs/Techniques%20Extra%20Info/Distillation.html" target="_blank">https://web.archive.org/web/20111008182346/http://www.chem.ualberta.ca/~orglabs/Techniques%20Extra%20Info/Distillation.html</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>"21 U.S. Code § 843 – Prohibited acts C". Legal Information Institute, Cornell University. <a href="https://www.law.cornell.edu/uscode/text/21/843" target="_blank">https://www.law.cornell.edu/uscode/text/21/843</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> </ol>