A reflux set-up with conically-tapered ground glass joints connecting the Graham condenser with the vacuum adapter (top) and two-necked flask. Another ground glass joint connects the second neck two another vacuum adapter.

Ground glass joints are used in laboratories to quickly and easily fit leak-tight apparatus together from commonly available parts. For example, a round bottom flask, Liebig condenser, and oil bubbler with ground glass joints may be rapidly fitted together to reflux a reaction mixture. This is a large improvement compared with older methods of custom-made glassware, which was time-consuming and expensive, or the use of less chemically- and heat-resistant corks or rubber bungs and glass tubes as joints which took time to prepare as well. Diagram of typical reflux apparatus. ... Categories: Laboratory equipment | Chemistry stubs ... Liebig condenser The Liebig condenser is a piece of laboratory equipment where a straight glass pipe goes through a water jacket (a glass cylinder through which water constantly flows). ... A simple oil bubbler. ... Diagram of typical reflux apparatus. ... A cork stopper for a wine bottle Champagne corks Varnished cork tiles can be used for flooring, as a substitute for linoleum or tiles. ...

To connect the hollow inner spaces of the glassware components, ground glass joints are hollow on the inside and open at the ends, except for stoppers.

History

Crude versions of conically-tapered ground glass joints have been made for quite a while, particularly for stoppers for glass bottles and retorts. These days, ground glass joints can be precisely ground to a reproducible taper or shape. They are made to join two glassware pieces together. One of the glassware items to be joined would have an inner (or male) joint with the ground glass surface facing outward and the other would have an outer (or female) joint of a correspondingly-fitting taper with the ground glass surface facing inward. Reusable glass milk bottles A bottle is a small container with a neck that is narrower than the body and a mouth. ... A retort. ... A sample ground glass showing the Academy 1. ...

Joint types

Two general types of ground glass joints are fairly commonly used: joints which are slightly conically-tapered and ball and socket joints(sometimes called spherical joints).

Conically-tapered joints

Standard Taper symbol

• The conically-tapered ground glass joints typically have a 1:10 taper and are often labeled with a symbol consisting of a capital T overlaid on a capital S which stands for "Standard Taper". This symbol is followed by a number, a slash, and another number. The first number represents the outer diameter in millimeters (mm) at the base of an inner joint or the inner diameter in mm at the tip of an outer joint, in both cases where the applicable diameter is at a maximum in the joint. The second number represents the ground glass length of the joint in mm. The most commonly encountered joints are 14/20 and 24/40. These joint sizes apply only to glassware in the US. There are also European ISO standard joints with common joint sizes of 10/19, 14/23 and 29/32. The stopper joints of chemical bottles, volumetric flasks, and separatory funnels often do not use the precision standard taper ground glass joints. Stopper joints are designated (if at all) only by the maximum diameter number.

Conically-tapered ground glass joints. Inner (male) joint shown on the left and outer (female) joint shown on the right. Ground glass surfaces are shown with gray shading. By putting them together in the direction of the arrows, they can be joined, usually with some grease applied to the ground glass surfaces.

Image File history File links Standard_Taper_Symbol. ... A millimetre (American spelling: millimeter), symbol mm is an SI unit of length that is equal to one thousandth of a metre. ... United States is the current Good Article Collaboration of the week! Please help to improve this article to the highest of standards. ... World map showing Europe A satellite composite image of Europe Europe is one of the six inhabited continents of the Earth. ... ISO has many meanings: Iso is the stem of the Latin transliteration of the Greek word ίσος (ísos, meaning equal). The iso- prefix in English derives from this and means equality or similarity. ... A volumetric flask (vol flask for short) is a piece of laboratory glassware used to measure a very precise and accurate amount of a liquid, and is used for such when the amount is too big for a pipette or burette. ... Separating funnel A separating funnel or separation funnel or separatory funnel is a piece of equipment used in science to separate two immiscible liquids or solutions of different densities. ... Image File history File links Conical_Ground_Glass_Joints. ...

Ball and socket joints

For ball and socket joints, the inner joint is a ball and the outer joint is a socket, both having holes leading to the interior of their respective tube ends to which they are fused. The ball tip is a hemisphere with a ground glass surface on the outside which fits inside of the socket where the ground glass surface is on the inside. Ball and socket joints are labeled with a size code consisting of a number, a slash, and another number. The first number represents the outer diameter in mm of the ball at its base or the inner diameter in mm at the tip of a socket, in both cases where the diameters are their maximum in the joints. The second number represents the inner diameter of the hole in the middle of the ball or socket, which leads to the inner diameter of the tube fused to the joint.

Ground glass ball (left) and socket (right) joints. The ground glass surfaces are shown with gray shading. By putting them together in the direction of the arrows, they can be joined, with some grease applied to the ground glass surfaces.

For either standard taper joints or ball and socket joints, inner and outer joints with the same numbers are made to fit together. When the joint sizes are different, ground glass adapters may be available (or made) to place in between to connect them. Special clips or pinch clamps may be placed around the union of the joints to help keep them together. Image File history File links Ball_and_socket_ground_glass_joints. ...

Round-bottom flasks often have one or more conically-tapered ground glass joint openings or necks. Conventionally, these joints at the flask necks are outer joints. Other adapters such as distillation heads and vacuum adapters are made with joints that fit in with this convention. If a flask or other container has an extra outer ground glass joint on it which needs to be closed off for an experiment, there are often conically-tapered inner ground glass stoppers available for such a purpose. In some cases, small hook-like protrusions made of glass may be fused onto the rest of the glass item near a joint to allow an end loop of a small spring to be attached so the spring helps keep joints temporarily together. The use of a special very small size of conically-tapered fitting for glass, plastic, or metal parts called a Luer fitting or adapter has become more widespread. Originally, Luer fittings were mostly used to connect the hub of a needle to a syringe. Where the use of ground glass presents a problem such as in the production or distillation of diazomethane, which may explode on contact with rougher surfaces, equipment with smooth glass joints may be used. Round-bottom flasks are types of flasks having spherical bottoms used as laboratory glassware, mostly for chemical or biochemical work. ... A syringe consists of a plunger fitted to a tube, called the barrel, which has a small opening on one end. ... Diazomethane is the chemical compound CH2N2. ...

Lubrication

Grease is used to lubricate glass stopcocks and joints. Some laboratories fill them into syringes for easy application. Two typical examples: Left - Krytox, a fluoroether-based grease; Right - a silicone-based high vacuum grease by Dow Corning.

A rather thin layer of grease particularly made for this application can be applied to the ground glass surfaces to be connected and the inner joint is inserted into the outer joint such that the ground glass surfaces of each are next to each other to make the connection. In addition to making a leak-tight connection, the grease allows to joints to be later separated more easily. Fairly recently, Teflon sleeves have been used in between joints to fit them together instead of grease. Grease is a lubricant of higher initial viscosity than oil, consisting originally of a calcium, sodium or lithium soap jelly emulsified with mineral oil. ... A syringe consists of a plunger fitted to a tube, called the barrel, which has a small opening on one end. ... Krytox is a trademark of a family of high performance synthetic lubricants (oils and greases) used in many things from spaceships to computer chips. ... Dow Corning is a multinational corporation headquartered in Midland, Michigan, USA. Dow Corning specializes in silicon and silicone-based technology and innovation, offering more than 7,000 products and services. ... Grease is a lubricant of higher initial viscosity than oil, consisting originally of a calcium, sodium or lithium soap jelly emulsified with mineral oil. ... Teflon is polytetrafluoroethylene (PTFE), a polymer of fluorinated ethylene. ...

See also

• Laboratory glassware