{"id":15907,"date":"2023-07-13T08:00:07","date_gmt":"2023-07-13T06:00:07","guid":{"rendered":"https:\/\/www.rct-online.de\/magazin\/?p=15907"},"modified":"2026-01-22T16:59:08","modified_gmt":"2026-01-22T15:59:08","slug":"standard-ground-joints-in-chemistry","status":"publish","type":"post","link":"https:\/\/www.rct-online.de\/magazin\/en\/standard-ground-joints-in-chemistry\/","title":{"rendered":"Standard Ground Joints in Chemistry"},"content":{"rendered":"<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_73 ez-toc-wrap-center counter-hierarchy ez-toc-counter ez-toc-white ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/standard-ground-joints-in-chemistry\/#Taper_Joints_%E2%80%93_The_Most_Common_Joint_Connection\" title=\"Taper Joints \u2013 The Most Common Joint Connection\">Taper Joints \u2013 The Most Common Joint Connection<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/standard-ground-joints-in-chemistry\/#Sealing_Taper-Joint_Connections\" title=\"Sealing Taper-Joint Connections\">Sealing Taper-Joint Connections<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/standard-ground-joints-in-chemistry\/#Connecting_Different_NS_Sizes\" title=\"Connecting Different NS Sizes\">Connecting Different NS Sizes<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/standard-ground-joints-in-chemistry\/#Where_Cylindrical_Joints_Are_Used\" title=\"Where Cylindrical Joints Are Used\">Where Cylindrical Joints Are Used<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/standard-ground-joints-in-chemistry\/#Spherical_Joints_%E2%80%93_The_Flexible_Joints\" title=\"Spherical Joints \u2013 The Flexible Joints\">Spherical Joints \u2013 The Flexible Joints<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/standard-ground-joints-in-chemistry\/#Flat_Planar_Joints\" title=\"Flat (Planar) Joints\">Flat (Planar) Joints<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/standard-ground-joints-in-chemistry\/#Types_of_Joint_Clamps\" title=\"Types of Joint Clamps\">Types of Joint Clamps<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/standard-ground-joints-in-chemistry\/#Various_Ground-Joint_Stoppers\" title=\"Various Ground-Joint Stoppers\">Various Ground-Joint Stoppers<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/www.rct-online.de\/magazin\/en\/standard-ground-joints-in-chemistry\/#Manufacturing_Standard_Ground_Joints\" title=\"Manufacturing Standard Ground Joints\">Manufacturing Standard Ground Joints<\/a><\/li><\/ul><\/nav><\/div>\n<p style=\"text-align: justify;\"><strong>In the chemical laboratory, many standards must be observed, including those for standard ground joints on laboratory apparatus or glass containers. Standard ground joints ensure that glassware and vessels, such as flasks and Liebig condensers, can be connected and sealed reliably. They are used in distillation and extraction setups, rotary evaporators, glass stoppers, and desiccators. <\/strong><\/p>\n<div class=\"box info  \"><div class=\"box-inner-block\"><i class=\"fa tie-shortcode-boxicon\"><\/i>\n\t\t\tStandard ground joints consist of a socket and a cone that fit into each other. The mating surface between the two is referred to as the ground joint. Ground Joints are available in different sizes and geometries, such as taper, cylindrical, spherical, and flat (planar) joints.\n\t\t\t<\/div><\/div>\n<h2><span class=\"ez-toc-section\" id=\"Taper_Joints_%E2%80%93_The_Most_Common_Joint_Connection\"><\/span>Taper Joints \u2013 The Most Common Joint Connection<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">With these standard ground joints, the mating surface between cone and socket is tapered, as shown in the figure below.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-15924 size-full\" title=\"Tapered mating surface between cone and socket\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2023\/07\/verbindung-kegelschliff_en.jpg\" alt=\"Tapered mating surface between cone and socket\" width=\"285\" height=\"142\" \/><\/p>\n<p style=\"text-align: justify;\">A taper-joint connection is suitable for vacuum use and rigid, which is why care must be taken to ensure a stress-free setup. The connection can additionally be secured with a <a href=\"https:\/\/www.rct-online.de\/en\/laboratory-equipment\/laboratory-semifinished-products-and-aids\/30036\/ground-joint-safety-clamp-made-of-pom\">joint clip<\/a>.<\/p>\n<p style=\"text-align: justify;\">The size designation uses the letters NS, the abbreviation for Normschliff (standard ground joint), followed by two dimensions: the first number indicates the larger diameter d2 and the second number indicates the length of the cone. Dimensions and tolerances for taper joints are defined in ISO 383, the international standard for interchangeable conical ground joints, which is published in Germany as DIN 12242 by the German standards body Deutsches Institut f\u00fcr Normung (DIN).<\/p>\n<div class=\"box note  \"><div class=\"box-inner-block\"><i class=\"fa tie-shortcode-boxicon\"><\/i>\n\t\t\tFor example, NS 29\/32 has a diameter of 29 mm and a length of 32 mm. Standard taper joints have a 1:10 taper (i.e., the diameter changes by 1 mm over 10 mm of length). This means the joint length determines the inner diameter d1.\n\t\t\t<\/div><\/div>\n<figure id=\"attachment_8889\" aria-describedby=\"caption-attachment-8889\" style=\"width: 450px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-8889 size-full\" title=\"Opened taper-joint connection between flask and condenser\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/geoeffnete-kegelschliff-verbindung.jpg\" alt=\"Opened taper-joint connection between flask and condenser\" width=\"450\" height=\"309\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/geoeffnete-kegelschliff-verbindung.jpg 450w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/geoeffnete-kegelschliff-verbindung-300x206.jpg 300w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/geoeffnete-kegelschliff-verbindung-110x75.jpg 110w\" sizes=\"(max-width: 450px) 100vw, 450px\" \/><figcaption id=\"caption-attachment-8889\" class=\"wp-caption-text\"><center>Opened taper-joint connection between flask and condenser<\/center><\/figcaption><\/figure>\n<p style=\"text-align: justify;\">The smallest size is NS 5\/13, the largest is NS 85\/55. Sizes NS 14\/23 and NS 29\/32 are used most frequently. In laboratory jargon, the length is usually omitted and people simply refer to a &#8220;14&#8221; or &#8220;29&#8221; joint. To securely seal <a href=\"https:\/\/www.rct-online.de\/en\/laboratory-equipment\/laboratory-containers\/measuring-beakers-and-measuring-flasks\/29817\/round-bottom-flask-with-standard-ground-glass-joint-made-of-pfa\">round-bottom flasks<\/a> and other <a href=\"https:\/\/www.rct-online.de\/en\/laboratory-equipment\/laboratory-containers\">laboratory containers<\/a> with a standard socket, suitable <a href=\"https:\/\/www.rct-online.de\/en\/laboratory-equipment\/laboratory-stoppers-and-caps\">laboratory stoppers<\/a> can be used.<\/p>\n<p><a href=\"https:\/\/www.rct-online.de\/en\/laboratory-equipment\/laboratory-containers\/measuring-beakers-and-measuring-flasks\/29817\/round-bottom-flask-with-standard-ground-glass-joint-made-of-pfa\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-8895 size-full\" title=\"Round-Bottom Flask with Standard Ground-Glass Joint made of PFA\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/messbecher-und-messkolben_normschliff-rundkolben-aus-pfa.jpg\" alt=\"Round-Bottom Flask with Standard Ground-Glass Joint made of PFA\" width=\"300\" height=\"300\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/messbecher-und-messkolben_normschliff-rundkolben-aus-pfa.jpg 300w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/messbecher-und-messkolben_normschliff-rundkolben-aus-pfa-150x150.jpg 150w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a> <a href=\"https:\/\/www.rct-online.de\/en\/laboratory-equipment\/laboratory-stoppers-and-caps\/30012\/standard-ground-joint-stopper-made-of-pp\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-8896 size-full\" title=\"Standard Ground Joint Stopper made of PP\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/laborstopfen-und-kappen-normschliff-stopfen-aus-pp.jpg\" alt=\"Standard Ground Joint Stopper made of PP\" width=\"300\" height=\"300\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/laborstopfen-und-kappen-normschliff-stopfen-aus-pp.jpg 300w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/laborstopfen-und-kappen-normschliff-stopfen-aus-pp-150x150.jpg 150w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><\/p>\n<p style=\"text-align: justify;\">In addition to the medium-length joints, long joints are also manufactured. A long version with a diameter of 14 mm has a length of 35 mm; with a diameter of 29 mm, the length is 42 mm. Because they provide a larger sealing surface, long joints are preferred for vacuum work.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Sealing_Taper-Joint_Connections\"><\/span>Sealing Taper-Joint Connections<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\">To seal the glass connection and prevent it from &#8220;sticking&#8221;, the joint is greased, for example with <a href=\"https:\/\/www.rct-online.de\/en\/adhesives-and-lubricants\/greases\">silicone-based greases<\/a>. Instead of greases, sleeves and sealing rings made of PTFE (polytetrafluoroethylene) are increasingly used today. Such seals made of plastics are low-maintenance, chemically resistant, reusable, and make it easier to separate the connection.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"Connecting_Different_NS_Sizes\"><\/span>Connecting Different NS Sizes<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p style=\"text-align: justify;\">Glassware with joints of different sizes can be connected using adapters, which are specified in DIN 12257, the German standard for ground-joint adapters. A reducing adapter connects a large cone to a smaller socket, for example a 19 cone to a 14 socket. The counterpart\u2014small cone to large socket\u2014is referred to as an expansion adapter.<\/p>\n<p style=\"text-align: justify;\">Taper joints are frequently used in the chemical laboratory. Examples of such glassware include laboratory containers such as round-bottom flasks, volumetric flasks, reflux condensers, distillation bridges, dropping funnels, and glass stoppers.<\/p>\n<h2 style=\"text-align: justify;\"><span class=\"ez-toc-section\" id=\"Where_Cylindrical_Joints_Are_Used\"><\/span>Where Cylindrical Joints Are Used<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">With cylindrical joints, the mating surface corresponds to the shape of a cylinder. The connection is not fixed; cone and socket can be moved axially relative to each other or rotated. Cylindrical joints are found in gas syringes used for dosing gases and referred to as piston samplers.<\/p>\n<p><a href=\"https:\/\/www.rct-online.de\/en\/laboratory-equipment\/ground-joint-components\/30020\/spherical-ground-joint-sleeve-made-of-ptfe\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-8897 size-full\" title=\"Spherical Ground Joint Sleeve made of PTFE\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/hochvakuum-griffbundrand-kugelschliff-dichtung-aus-ptfe.jpg\" alt=\"Spherical Ground Joint Sleeve made of PTFE\" width=\"300\" height=\"300\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/hochvakuum-griffbundrand-kugelschliff-dichtung-aus-ptfe.jpg 300w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/hochvakuum-griffbundrand-kugelschliff-dichtung-aus-ptfe-150x150.jpg 150w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a> <a href=\"https:\/\/www.rct-online.de\/en\/laboratory-equipment\/ground-joint-components\/30019\/sleeve-with-gripping-ring-made-of-ptfe\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-8898 size-full\" title=\"Sleeve with Gripping Ring made of PTFE\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/hochvakuum-griffbundrand-kegelschliff-dichtung-aus-ptfe.jpg\" alt=\"Sleeve with Gripping Ring made of PTFE\" width=\"300\" height=\"300\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/hochvakuum-griffbundrand-kegelschliff-dichtung-aus-ptfe.jpg 300w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/hochvakuum-griffbundrand-kegelschliff-dichtung-aus-ptfe-150x150.jpg 150w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><\/p>\n<p style=\"text-align: justify;\">Cylindrical joints are also used as guides for rotating shafts such as KPG stirrers\u2014an abbreviation for &#8220;kerngezogenes Pr\u00e4zisions-Glasger\u00e4t&#8221; (core-drawn precision glassware). KPG stirrers consist of a stirring sleeve and a stirring shaft with a precision cylindrical fit, so the shaft can rotate with an exact fit inside the sleeve. These glass laboratory devices are used for stirring liquids when <a href=\"https:\/\/www.rct-online.de\/en\/laboratory-equipment\/stirring-and-mixing\/stirrers-and-stirring-devices\">magnetic stirrers<\/a> are not sufficient.<\/p>\n<p style=\"text-align: justify;\">This is the case when stirring viscous liquids, when a solid forms during a reaction taking place in the stirring vessel, when a high stirring speed is required, or when working with a large reaction batch.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Spherical_Joints_%E2%80%93_The_Flexible_Joints\"><\/span>Spherical Joints \u2013 The Flexible Joints<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">Instead of cone and socket, spherical joints consist of a ball and a socket (cup), with spherical mating surfaces that can move freely against each other around the centre of the ball. This makes these connections more flexible than others; however, they must be secured with clamps.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter wp-image-8884 size-full\" title=\"Spherical mating surfaces\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/verbindung-kugelschliff.jpg\" alt=\"Schematic representation of a spherical connection\" width=\"337\" height=\"169\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/verbindung-kugelschliff.jpg 337w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/verbindung-kugelschliff-300x150.jpg 300w\" sizes=\"(max-width: 337px) 100vw, 337px\" \/><\/p>\n<p style=\"text-align: justify;\">Spherical joints are designated with the letter S, from the English &#8220;spherical&#8221;, and the rounded cone diameter. They are offered in sizes from S 13 to S 64. In addition to adapters for different sizes, there are also adapters from ball to taper and vice versa.<\/p>\n<p style=\"text-align: justify;\">Spherical joints are more expensive than other joints, but they have the advantage that they cannot &#8220;seize&#8221;, i.e., they do not jam in such a way that they become difficult to separate. They can be found on flasks connected to rotary evaporators, on vacuum traps, and on condensate separators of diaphragm pumps.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Flat_Planar_Joints\"><\/span>Flat (Planar) Joints<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">Flat joints are characterised by completely level ground surfaces. They cannot be inserted into each other and are freely movable radially. The dimensions of and requirements for tube ends and lids with flat joints are specified in DIN 12214, the German standard for flat ground joints. In the <a href=\"https:\/\/www.rct-online.de\/en\/laboratory-equipment\">laboratory supplies<\/a> range, round, standardised flat joints with diameters of 35, 60, 100, 120, 150, and 200 mm are available. They are used in <a href=\"https:\/\/www.rct-online.de\/en\/laboratory-equipment\/laboratory-containers\/test-tube-racks-and-desiccators\">desiccators<\/a>, flat-joint lids for glass reactors, and vacuum bells.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Types_of_Joint_Clamps\"><\/span>Types of Joint Clamps<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">A clamp prevents the cone and socket from sliding apart under tensile or compressive load. In laboratory supplies, clamps made of metal or plastic are available. Plastic clamps are usually made of polyoxymethylene (POM), which is characterised by good chemical resistance and autoclavability and can be used at temperatures up to +150 \u00b0C.<\/p>\n<p><a href=\"https:\/\/www.rct-online.de\/en\/laboratory-equipment\/laboratory-semifinished-products-and-aids\/30036\/ground-joint-safety-clamp-made-of-pom\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-13122 size-full\" title=\"Ground Joint Safety Clamp made of POM\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/schliff-und-sicherheitsklammer-aus-pom.jpg\" alt=\"Ground Joint Safety Clamp made of POM\" width=\"300\" height=\"300\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/schliff-und-sicherheitsklammer-aus-pom.jpg 300w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/schliff-und-sicherheitsklammer-aus-pom-150x150.jpg 150w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a> <a href=\"https:\/\/www.rct-online.de\/en\/laboratory-equipment\/laboratory-stoppers-and-caps\/30013\/standard-ground-joint-stopper-made-of-ptfe\"><img loading=\"lazy\" decoding=\"async\" class=\"alignnone wp-image-8900 size-full\" title=\"Standard Ground Joint Stopper made of PTFE\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/laborstopfen-und-kappen_normschliff-stopfen-aus-ptfe.jpg\" alt=\"Standard Ground Joint Stopper made of PTFE\" width=\"300\" height=\"300\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/laborstopfen-und-kappen_normschliff-stopfen-aus-ptfe.jpg 300w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/laborstopfen-und-kappen_normschliff-stopfen-aus-ptfe-150x150.jpg 150w\" sizes=\"(max-width: 300px) 100vw, 300px\" \/><\/a><\/p>\n<p style=\"text-align: justify;\">These safety clamps are colour-coded by size, do not bend, and are suitable for both taper and spherical types. They are also known as Keck clips, named after the German chemist Hermann Keck (1919\u20132010), who received a patent for them in 1984.<\/p>\n<p style=\"text-align: justify;\">Clamps made of PTFE with an encapsulated steel spring are also offered, as well as versions made of metallic alloys such as V2A spring steel, which are attached according to the functional principle of clothes pegs and can additionally be secured with a knurled set screw.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Various_Ground-Joint_Stoppers\"><\/span>Various Ground-Joint Stoppers<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">To seal glassware, <a href=\"https:\/\/www.rct-online.de\/en\/laboratory-equipment\/laboratory-stoppers-and-caps\/30012\/standard-ground-joint-stopper-made-of-pp\">ground-joint stoppers<\/a>, mainly with taper joints, are used. They are made of plastics such as polypropylene (PP), low-density polyethylene (PE-LD), and PTFE, or glass, and are usually equipped with a hexagonal or octagonal cap.<\/p>\n<p style=\"text-align: justify;\">Glass ground-joint stoppers can be solid or hollow, with hollow stoppers being lighter but also more expensive due to the more complex manufacturing. Hollow ground-joint stoppers are available with a flat or pointed base. Glass ground-joint stoppers are offered in clear and amber glass.<\/p>\n<h2><span class=\"ez-toc-section\" id=\"Manufacturing_Standard_Ground_Joints\"><\/span>Manufacturing Standard Ground Joints<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p style=\"text-align: justify;\">To meet the standards&#8217; requirements for dimensions and tolerances, both a complex production process and careful quality control are necessary. First, glass tubing is heated to a viscous state and a joint blank is produced using a glass-forming machine. In several steps, socket and cone are ground to the required roughness. Conicity, roundness, wall thickness, and roughness are checked.<\/p>\n<figure id=\"attachment_8891\" aria-describedby=\"caption-attachment-8891\" style=\"width: 450px\" class=\"wp-caption aligncenter\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-8891 size-full\" title=\"Glass dropping funnel with taper-joint connections\" src=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/tropftrichter-aus-glas.jpg\" alt=\"Glass dropping funnel with taper-joint connections\" width=\"450\" height=\"609\" srcset=\"https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/tropftrichter-aus-glas.jpg 450w, https:\/\/www.rct-online.de\/magazin\/wp-content\/uploads\/2024\/07\/tropftrichter-aus-glas-222x300.jpg 222w\" sizes=\"(max-width: 450px) 100vw, 450px\" \/><figcaption id=\"caption-attachment-8891\" class=\"wp-caption-text\"><center>Glass dropping funnel with taper-joint connections<\/center><\/figcaption><\/figure>\n<p style=\"text-align: justify;\">Standard ground joints play an important role, above all, in preparative organic chemistry. They make it possible to assemble complex glass apparatus for the synthesis, purification, and concentration of chemical compounds.<\/p>\n<pre><strong>Image Sources:<\/strong>\r\nCover image | \u00a9 Souvik \u2013 stock.adobe.com\r\nOpened taper-joint connection | \u00a9 Phasmatisnox on English Wikipedia, CC BY-SA 3.0 &lt;https:\/\/creativecommons.org\/licenses\/by-sa\/3.0&gt;, via Wikimedia Commons\r\nGlass dropping funnel | \u00a9 Ichwarsnur, CC BY-SA 4.0 &lt;https:\/\/creativecommons.org\/licenses\/by-sa\/4.0&gt;, via Wikimedia Commons\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>In the chemical laboratory, many standards must be observed, including those for standard ground joints on laboratory apparatus or glass containers. Standard ground joints ensure that glassware and vessels, such as flasks and Liebig condensers, can be connected and sealed reliably. They are used in distillation and extraction setups, rotary evaporators, glass stoppers, and desiccators. &hellip;<\/p>\n","protected":false},"author":13,"featured_media":13115,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1,3028,2744],"tags":[3829,3822,3811,3826,3827,3825,3824,3815,3816,3812,3817,3823,3828,3810,3814,3818,3820,3819,3821,3813],"class_list":["post-15907","post","type-post","status-publish","format-standard","has-post-thumbnail","","category-all-articles","category-alle-beitraege-en","category-chemical-technology-in-action","tag-cylindrical-joints","tag-flat-joints","tag-glass-ground-joint-stoppers","tag-ground-joint-connections","tag-ground-joint-connections-in-the-laboratory","tag-ground-joint-stoppers","tag-joint-clamp","tag-laboratory-containers-with-standard-ground-joint-socket","tag-long-joints","tag-manufacturing-standard-ground-joints","tag-medium-length-joints","tag-plastic-joint-seals","tag-safety-clamps","tag-sealing-taper-joint-connections","tag-spherical-joints","tag-standard-ground-joint-diameter","tag-standard-ground-joint-dimensions","tag-standard-ground-joint-size","tag-standard-ground-joints-in-chemistry","tag-taper-joint-connection"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v23.1 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Standard Ground Joints in Chemistry - Reichelt Chemietechnik Magazine<\/title>\n<meta name=\"description\" content=\"What are standard ground joints, what types exist, and where are they used in the lab? 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