Laboratory glassware refers to a variety of equipment, traditionally made of glass, used for scientific experiments and other work in science, especially in chemistry and biology laboratories. Especially borosilicate glass, pioneered by Otto Schott, or sodalime glass are preferred glass types for scientific experiments and other work in science, especially in chemistry and biology laboratories.
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Applications
Glass use in laboratory applications is not as commonplace as it once was because of cheaper, less breakable, plasticware; however, certain applications still require glassware because glass is relatively inert, transparent, heat-resistant, and easy to customize. There are several types of glass, each used for different purposes. Borosilicate glass, which is commonly used in reagent bottles, can withstand thermal stress. Quartz glass, which is common in cuvettes, can withstand high temperatures and is transparent in certain parts of the electromagnetic spectrum. Darkened brown or amber (actinic) glass, which is common in dark storage bottles, can block ultraviolet and infrared radiation. Heavy-wall glass, which is common in glass pressure reactors, can withstand pressurized applications.
Examples
There are many different kinds of laboratory glassware items.
Examples of glassware containers include:
- Beakers are simple cylindrical shaped containers used to hold reagents or samples.
- Flasks are narrow-necked glass containers, typically conical or spherical, used in a laboratory to hold reagents or samples. Examples flasks include the Erlenmeyer flasks and Florence flasks.
- Bottles are containers with narrow openings generally used to store reagents or samples. Small bottles are called vials.
- Jars are cylindrical containers with wide openings that may be sealed. Bell jars are used to contain vacuums.
- Watch glasses are shallow glass dishes used as an evaporating surface or to cover a beaker.
- Test tubes are used by chemists to hold, mix, or heat small quantities of solid or liquid chemicals, especially for qualitative experiments and assays
- Desiccators of glass construction are used to dry materials or keep material dry.
- Glass evaporating dishes are used to evaporate materials.
- Microscope slides are thin strips used to hold items under a microscope.
- Glass petri dishes are used to culture living cells.
Examples of glassware used for measurements include:
- Graduated cylinders are cylindrical containers used for volumetric measurements.
- Burettes are used to disperse precise amounts of liquid reagents.
- Glass pipettes are used to transfer precise quantities of fluids.
- Glass Ebulliometers are used to accurately measure the boiling point of liquids.
Other examples of glassware includes:
- Glass tubes are cylindrical pieces of glassware used to hold or transport fluids.
- Stirring rods are used to mix chemicals.
- Funnels are used to get materials through a narrow opening.
- Condensers are used to cool hot liquids or vapors.
- Glass retorts are used for distillation.
- Drying pistols are used to free samples from traces of water, or other impurities.
Production
Most laboratory glassware is currently mass-produced, but large laboratories may employ a glass blower to construct specialized pieces. This construction forms a specialized field of glassblowing requiring precise control of shape and dimension. In addition to repairing expensive or difficult-to-replace glassware, scientific glassblowing commonly involves fusing together various glass parts--such as glass joints and tubing, stopcocks, transition pieces, and/or other glassware or parts of them to form items of glassware, such as vacuum manifolds, special reaction flasks, etc.
Various types of joints and stopcocks are available separately and come fused with a length of glass tubing, which a glassblower may use to fuse to another piece of glassware.
Features and accessories
When in use, laboratory glassware is often held in place with clamps made for that purpose, which are likewise attached and held in place by stands or racks. This article covers aspects of laboratory glassware which may be common to several kinds of glassware and may briefly describe a few glassware items not covered in other articles. Describing glassware can be complicated since manufacturers provide conflicting names for glassware. For example, what ChemGlass calls a glass stopcock, Kontes calls a glass plug.
Stoppers
Stoppers are used to seal certain types of glassware. These may be made out of glass as well as other materials including rubber or cork.
Coatings
Glassware may be coated to reduce the occurrence of breakage or failure.
Connectors
- Ground glass joints composed of all glass quickly and easily fit leak-tight apparatus together.
- Glass connectors or adapters are hollow glassware components with ground glass joints open at one or both ends.
- Hose barbs are cylindrical tubes with barbs used to attach hoses and flexible tubing to glassware.
- Keck clips and other clamping methods can be used to hold glassware together.
- Glass tubes, T-connectors, and Y-connectors may be used as interconnecting components.
- Rubber bungs or stoppers may hold glassware together.
Glassware valves
Valves are used to redirect flows through pipes. Two types of valves used in laboratory glassware are the stopcock valve and the threaded plug valve. These and other terms used below are defined in detail since they are bound to conflict with different sources.
Stopcock valve
Stopcocks are a smooth tapered plug or rotor with a handle, which fits into a corresponding ground glass female joint. Stopcocks are often parts of laboratory glassware such as burettes, separatory funnels, Schlenk flasks, and columns used for column chromatography.
Threaded plug valve
Threaded plug valves are used significantly in air-sensitive chemistry as well as when a vessel must be closed completely as in the case of Schlenk bombs. The construction of a threaded plug valve involves a plug with a threaded cap which are made so that they fit with the threading on a corresponding piece of female glass. Screwing the plug in part-way first engages one or more O-rings, made of rubber or plastic, near the plug's base, which seals the female joint off from the outer atmosphere. Screwing the plug valve all the way in engages the plug's tip with a beveled constriction in the glass, which provides a second seal. This seal separates the region beyond the bevel and the O-rings already mentioned.
With solid plugs, a tube or area exists above and below the bevel and turning the plug controls access. In a number of cases it is convenient to fully remove a plug which can give access to the region beyond the bevel. Plugs are generally made of an inert plastic such as PTFE and are attached to a threaded sleeve in such a way that the sleeve can be turned without spinning the plug. The contact with the bevel is made by an O-ring fitted to the tip of the plug or by the plug itself. There are a few examples where the plug in made of glass. In the case of glass plugs, the joint contact is always a rubber O-ring but they are still prone to shattering.
Not all plugs are solid. Some plugs are bored with a T-junction. In these systems the plug extends beyond the threaded sleeve and is designed to form an airtight fitting with glass tubing or hosing. The shaft of the plug is bored from beyond the threaded sleeve to a T-junction just before the bevel plug contact. When the plug is fully sealed, the region beyond the bevel is separated from the plug shaft as well as the bore which leads out of its shaft. When the plug bevel contact is released, the two regions are exposed to each other. These valves have also been used as a grease-free alternative to straight bored stopcocks common to Schlenk flasks. The high symmetry and concise design of these valves has also made them popular for capping NMR tubes. Such NMR tubes can be heated without the loss of solvent thanks to the valve's gas-tight seal. NMR tubes with T-bore plugs are widely known as J. Young NMR tubes, named after the brand name of valves most commonly used for this purpose. Images of J. Young NMR tubes and a J. Young NMR tube adapter are in the gallery.
Glass valves
Valves made entirely of glass may be used to restrict fluid flows.
Fritted glass
Fritted glass is finely porous glass through which gas or liquid may pass. Applications in laboratory glassware include use in fritted glass filter items, scrubbers, or spargers. Other laboratory applications of fritted glass include packing in chromatography columns and resin beds for special chemical synthesis.
Source of the article : Wikipedia
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